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From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: Machined rims, was Re: rim cracks - advice needed
Date: Mon, 1 Apr 1996 20:36:03 GMT
Jason Kangas writes:
> You may be overlooking the fact that Mavic first started machining
> their rims after they welded the joint. The welded joint has to be
> one of the strongest methods for joining a rim. The machining of the
> rim was designed to remove the excess weld material and create a
> consistent braking track. Also, by anodizing the rim first and then
> removing the slippery process from the side of the rim, certain
> cosmetic effects are possible without the normal uneven look of
> partially worn off anodizing.
I'm not overlooking that at all. The bicycle industry is run by
people as unclear on technical matters as the average wreck.bike
experts who expound upon things about which they know little. That
rims do not require any fastening at the joint, completely escapes
them. They could not have done an analysis of this joint or they
would recognize the foolishness that welded joints are. It's an
old "idee fixe" that wants a continuous perfect circle without joint.
Fiamme made rims that all had a ding in the joint because some well
meaning person thought the rims would separate if they weren't
riveted. The riveting machine deformed the profile on both sides of
the joint. This, even though Fiamme had earlier made a whole series
of rims that were smooth and had no rivets, similar to Mavic's butt
joined rims, rims that formerly could be pulled apart although I
almost suspect Mavic now glues them. The joint is held together by
about 1000 pounds force when the spokes of a wheel are tightened.
That they anodize rims is proof that no one is technically at home
there. Materials science literature has ample publications concerning
the fatigue susceptibility of aluminum parts coated with brittle
porous hard coatings (anodizing). The aircraft industry, long ago,
made these discoveries but the bicycle trade, that is mostly driven by
fashion and managed by non technical people, must go through the long
arduous process of first hand experience.
The subject of tire treads is classic in that it is driven entirely by
marketing considerations. The scientific method is not employed here.
Similarly cranks are being offered in forms that have no relation to
their stresses. Most NC machined cranks have minimal torsional
strength and do not address the principal failure modes, but they sure
look techie! I think the "Don't lubricate the spindle press fit"
admonition screams of failure understand cause and effect.
Jobst Brandt <jbrandt@hpl.hp.com>
Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: rim cracks - advice needed
Date: Wed, 3 Apr 1996 19:01:55 GMT
Eric Peltier writes:
>> My point is that I keep hearing of advances in technology such as
>> "hard anodized", "precision machined" and other gratuitous expenses
>> heaped on where they offer nothing but cost. Meanwhile standard rims
>> like the MA-2, formerly called Super Champion Gentleman before Mavic...
> What is your opinion about "ceramic" coatings on the Mavics and the
> Tungsten Carbide Cobalt coating on the Sun MA17's?
Ceramics are insulators, both electrical and thermal, so the braking
energy converted to heat in the brake pad cannot transfer to the
aluminum rim where it can be dissipated. The result is rapid pad wear
and reduced brake effect. The main benefit was intended to be for wet
braking, where water lubrication makes soft pads on wet metal rims
ineffective. Its resistance to wear is probably also a goal for wet
conditions that circulate much grit.
> I just finished up lacing the front wheel with a TCC rim from Sun,
> and had done the rear just before Moab a few weeks ago. It braked
> VERY well in dry weather, but I didn't get to try it in the wet,
> even yet.
I don't know what you call "VERY good" or how you measured it. At low
speed pad heating should not be noticeable but at higher speeds I
expect pad wear to accelerate and retardation to become perceptibly
poorer. I haven't seen any TCC coated rims but I have tried hard
anodized ones that fit the same ceramic description only that the
coating is thin. Even at that they respond more poorly than bare rims.
Jobst Brandt <jbrandt@hpl.hp.com>
Date: 04 Apr 1996
From: hajo@quijote.in-berlin.de (Hans-Joachim Zierke)
Newsgroups: rec.bicycles.tech
Subject: Re: rim cracks - advice needed
Jobst Brandt writes:
> I disagree. I have perfectly smooth continuous rims from Fiamme,
> Super Champion, Ritchey, Campagnolo and Mavic, that are made from
> coiled extrusions. Besides that, I have a stack of worn out rims that
> have such a smooth joint from braking that the crack is hard to find.
Any rim is smooth after enough braking in the wet. For a considerable
number of cyclists, this needs some years. The only company that managed to
manufacture really good rim joints with the traditional method was Campy. I
have seen and ridden several bikes with rim joints that generated interval
brake action.
In fact, one of the two times when I was threatened to sue me for a bike
magazine article, it was for an article about rims with joints of the
"danger" class. This was a funny incident. While the threatening was good
for a laughter, press company CEOs often don't like this kind of mail from
manufacturers. But this time, the company CEO had taken one of our test
bikes for his personal holiday, and returned with the comment that the bike
had been fun, but the rims were so bad that braking was dangerous. And that
we should write something about it. It was the same rim.
The editor smiled and presented the letter with the threatening to sue us
for doing just that. I rolled on the floor laughing when he told me the
story.
> My point is that I keep hearing of advances in technology such as
> "hard anodized", "precision machined" and other gratuitous expenses
> heaped on where they offer nothing but cost.
I agree that "precision machined" is just marketing words garbage. But I
like marketing gags like the one of Ambrosio. They put a "0.02" sticker on
the rim, defining the guaranteed precision at the rim joint. I do not care
a lot _how_ they do it, wether by traditional means, or by machining, or
whatever, I just like good rim joints, that endanger nobody.
> Meanwhile standard rims
> like the MA-2, formerly called Super Champion Gentleman before Mavic
> bought the company, become unavailable because glitzy machined and
> colored rims displace them.
I don't think so. The glitzy machine work replaces purple anodizing. An
industry salesman just told me that "polished" is the HOT rim fashion for
'96.
About 8 years ago, I did a stupid student job in a bike shop. Building
wheels with payment per wheel, stress relieved, high spoke force, built to
defined precision (we had trueing stands with analog precision displacement
metering).
I would have earned my living with good income if I had built a wheel every
40 minutes. This is possible with good tools (like ratcheting screwdrivers
with special blades, a desk with right height, a perfect trueing stand),
and good spoke length tables at the wall. All this was present in this
shop.
Unluckiliy, it also needs rims with good joints, that allow precision
without playing lots of tricks first. With the Mavic Reflex rims of today,
I think I would have done it in 25 - 30 minutes after some weeks of work,
and had been a rich student.
I had to quit that job instead. Too much MA-2s.
> > Niemand übertrifft mich an Bescheidenheit.
>
> Wie soll ich diesen Spruch anbringen?
I like it. An elegant contradiction in itself, using a complete sentence
of only 5 words. I think it is a piece of art. Unluckily, I haven't
invented it, but stolen from Sartre.
hajo
--
Niemand übertrifft mich an Bescheidenheit.
Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: rim cracks - advice needed
Date: Thu, 4 Apr 1996 17:40:35 GMT
Paul Umbanhowar (aka Greg Lewis) writes: [Unabomber?]
> I think you are probably right about the ceramic rims but since it
> seems to be almost entirely based on theory I'll question some of it.
This is not theory but practice. I have burned off brake pads with
these things and have no room for that kind of misplaced technology.
> Ceramics are insulators but so are brake pads. Still seems like the
> majority of heat must be transfered to the rim any way. This coating
> is probably fairly thin and the rim has so much more area and thermal
> mass than the pads that I would still think it absorbs a lot of heat.
When two things rub, heat is generated IN the softer material, not at
the interface, as one often hears. Heat is generated in the face of
the brake pad with high frequency waves known as Schallamach waves.
These occur in several modes that each have a characteristic
frequency, thus we have constant pitch brake squeal over a fairly wide
velocity range is common with bicycles as it is with cars. Skidding
car tires similarly have a constant pitch for the same reason.
These vibrations generate heat in the face of the pad, but because the
pad is an insulator, the heat must dissipated by the rim. Mathauser
puts cooling fins on the back side of brake pads because he is unaware
of this. His heat sinks are mere eyewash. In the millisecond or two
that it takes for a ceramic coated rim to pass the pad at higher
speed, the rim appears as an insulator if. The thermal gradient
through the insulator, as thin as it is, affects the surface
temperature substantially because the heating is concentrated and
short in duration. The underlying conductivity is masked before any
substantial heat can penetrate. Thus, at a "glance" the rim appears
largely ceramic.
> Do you know how the friction characteristics of the pads change with
> temperature? How hot the pads can get before degrading? I imagine
> there is a fair amount of variation between brands.
I haven't made any measurements but I have tried many pads and found
the most stable, durable, and least likely to generate embedded hard
particles to be the red Kool Stop material, the same used today in
Ritchey and Mathauser pads. I use the old clod shaped one piece Kool
Stop pads.
> I've heard of people melting brake blocks but I've had more trouble
> with tires blowing out than pads melting. The decreased heat
> transfer to the rims would help in this case.
Pad melting is an immediate problem, hot tires is a longer term one.
Ultimately the heat must go into the rim. It can't get out any other
way, so the ceramic only makes the pad operate at higher temperature,
or it will limit braking when the pad material breaks down.
> I've been told that the ceramic increases friction and that it makes
> a big difference in stopping power. (This was told to me by a bike
> shop employee so I am remaining skeptical). Granted the pads may
> wear out quicker but if the increased friction produces better
> braking that may be a small price to pay.
That depends on what you mean by friction. Tribology is a largely
misunderstood subject. It includes people who want to maximize wear
and minimize frictional drag (abrasives), minimize wear and maximize
frictional drag (brakes and clutches), minimize wear and drag,
(lubricant and bearings), and maximize wear and drag (demolition).
Increasing friction with ceramics is done at the expense of
demolition type tribology. In dry conditions it melts pads.
> If the ceramic increase friction and also prevents significant heat
> transfer to the rims, it may be a disadvantage in the mountains
> where braking occurs for long periods, but an advantage in less
> hilly terrain where heating occurs more intermittently.
The time constant at speeds of interest is in fractions of seconds,
not several seconds.
> So I remain skeptical of all claims about ceramic rims without more
> evidence. In the mean time I'll stick to my MA-2's.
That's my choice as well.
Jobst Brandt <jbrandt@hpl.hp.com>
Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: Mavic failure
Date: Thu, 4 Apr 1996 17:51:54 GMT
Arne R|kkum writes:
> Yesterday the tube burst a few seconds after that I had put 70 psi
> into it. This was the occasion of spring cleaning, so I had just
> inspected the rim, finding it fine. Now the outer edge of the rim
> burst along with the tube, from the tube valve hole and onward. The
> exploding tube caused the metal to burst, producing a spike-like
> offshoot.
Can you describe the failure in more detail? Where was the rim
fracture and how thick was the material at the failure. The way you
describe the break, I get the impression that it failed in the central
plane of the rim, along the spoke holes. Is this correct.
> Or can it, unless this rear wheel has an initial metal fatigue? I
> would appreciate very much any comment on the issue, including the
> nature of Mavic accidents.
Metal fatigue occurs when the cyclic stresses of use are too high and
this can occur either because the material was too thin or the
extrusion was faulty, having a bad "weld". Most extrusions have a
closure seam that allows the core for a hollow cross section to be
suspended from the side of the die. The closure "weld" where the
metal meets before exiting the die must be suitably located to avoid
fractures in use. This seam can often be detected by inspecting the
unpolished inside of the extrusion or by chemical etching.
Please tell me more.
Jobst Brandt <jbrandt@hpl.hp.com>
Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: rim cracks - advice needed
Date: Fri, 5 Apr 1996 02:28:16 GMT
Greg Lewis writes:
>> When two things rub, heat is generated IN the softer material, not at
>> the interface, as one often hears. Heat is generated in the face of
>> the brake pad with high frequency waves known as Schallamach waves.
>> These occur in several modes that each have a characteristic
>> frequency, thus we have constant pitch brake squeal over a fairly wide
>> velocity range is common with bicycles as it is with cars. Skidding
>> car tires similarly have a constant pitch for the same reason.
> This is interesting. We really hearing the pad vibrate, or is it
> amplified by the rim and brake?
I'm sure there is some sounding board effect but the frequency comes from
the pad material, just as it does form a skidding car tire. The road, in
that event does not resonate.
>> These vibrations generate heat in the face of the pad, but because the
>> pad is an insulator, the heat must dissipated by the rim. Mathauser
>> puts cooling fins on the back side of brake pads because he is unaware
>> of this. His heat sinks are mere eyewash. In the millisecond or two
>> that it takes for a ceramic coated rim to pass the pad at higher
>> speed, the rim appears as an insulator if. The thermal gradient
>> through the insulator, as thin as it is, affects the surface
>> temperature substantially because the heating is concentrated and
>> short in duration. The underlying conductivity is masked before any
>> substantial heat can penetrate. Thus, at a "glance" the rim appears
>> largely ceramic.
> So the surface temperature of ceramic coated rims remains higher
> because the heat does not get conducted into the rim interior.
> In this case isn't the relevant time scale the rotation period of
> the rim? That is the amount of time the heat at the surface can be
> dissipated. I don't see how the short time scale that a section of
> rim is in contact with the pad effects the insulating properties.
> Am I missing something?
The heat causes a temperature gradient that leaves the surface of the
rim and more importantly, the pad at a higher temperature. The pad
faces and insulator that is unwilling to accept heat. If it took
longer, the rim would heat up, but in this case less heat gets that
far than it would with no ceramic. The pad gets heated to its melting
point or at least closer to it than if it were running against
aluminum, the material it was designed for.
This is similar to the mechanic who said the reason the car boiled
over was that the water was going through the radiator to fast and
that a flow restricter would enhance cooling. This does not work.
>> Pad melting is an immediate problem, hot tires is a longer term one.
>> Ultimately the heat must go into the rim. It can't get out any other
>> way, so the ceramic only makes the pad operate at higher temperature,
>> or it will limit braking when the pad material breaks down.
> Ultimately the heat must go into the surrounding air. Again I've
> not had trouble with pad melting. If I understand you, you have had
> pad melting limit the braking power, not just reduced the pad life.
> Is that correct?
Either into the surrounding air or not get generated in the first
place, and that is what overheated brakes do. They cease to convert
kinetic energy to heat. That's what an insulator as a heat sink does
for brakes.
> Is the black coating left on rims from pad melting?
I don't get black streaks from my pads, nor do I get gouges from
embedded debris.
>>> I've been told that the ceramic increases friction and that it makes
>>> a big difference in stopping power. (This was told to me by a bike
>>> shop employee so I am remaining skeptical). Granted the pads may
>>> wear out quicker but if the increased friction produces better
>>> braking that may be a small price to pay.
>> That depends on what you mean by friction. Tribology is a largely
>> misunderstood subject. It includes people who want to maximize wear
>> and minimize frictional drag (abrasives), minimize wear and maximize
>> frictional drag (brakes and clutches), minimize wear and drag,
>> (lubricant and bearings), and maximize wear and drag (demolition).
>> Increasing friction with ceramics is done at the expense of
>> demolition type tribology. In dry conditions it melts pads.
>>> If the ceramic increase friction and also prevents significant heat
>>> transfer to the rims, it may be a disadvantage in the mountains
>>> where braking occurs for long periods, but an advantage in less
>>> hilly terrain where heating occurs more intermittently.
>> The time constant at speeds of interest is in fractions of seconds,
>> not several seconds.
> This again does not make sense to me. The short time scale is what
> determines the heat generation, but the temperature of the pads
> and rims are greatly effected by how long the heat is being
> generated. Pad melting will be much greater if the rim is heated
> up to 200 degrees from long descents.
And heat generated and dissipated by the remainder of the rim is
diminished and the brake pads become less able to convert energy to
heat as they get softer in the portion that is active in doing so.
> I'd like to see a demonstration of some pad melting from one stop.
> Pick and hill, get up to a good high speed and show me that you can
> melt a typical pad from one stop.
I have old Mathauser pads that were to soft or low temperature that
demonstrate the problem clearly. These pads worked well just riding
down the avenue but a hard application going into a turn was grabby at
first and then fade. The pad surface has flow marks as if it had been
held up to a heat lamp to melt. Ceramic will do the same to an
otherwise suitable brake pad. My first experience with this was with
wood rims that seemed OK until I tried to descend. The hot rubber of
my Universal brakes burned my legs as the bits came flying off. Wood
is an insulator but it works pretty good in the rain and it won't melt
the glue that holds on tubular tires.
> Or how about showing me that braking distance is increased because of
> ceramic rims. Again from one stop. If you can then I'll believe you
> about the time scales.
Don't believe it. I have no great interest in proving with research
how bad a bad idea is. Not long ago a similar challenge was thrown my
way for believers in FiberFlite spokes. I have the spokes and the
test fixture but I never got around to testing them because the whole
idea went away before I measured anything. This sort of stuff comes
up all the time. I have better things to do. How about you showing
that ceramic rims have reasonable benefits. I've tried lots of
equipment in my time on the bicycle and I've tried these rims to my
satisfaction.
> If anyone gets the chance to do this test please post the results.
> (you need two identical front wheels except on is ceramic coated
> and the other is plain aluminum. The pads and rim need to clean,
> practice runs are necessary to make sure the stopping distance is
> the minimum possible.) This should really be a double blind test
> (difficult), and repeated by several riders in both wet and
> dry conditions.
Thanks for giving us all a homework assignment. I think I'll pass.
> I'm still not convinced ceramic necessarily results in worse
> braking. For someone who is light and does not ride mountains,
> the temperatures might not ever get high enough to matter.
> For you it is another matter.
Well, convince yourself. It is not in my interest to convert non
believers. I'm just telling you why they don't work and what the
principals are.
Jobst Brandt <jbrandt@hpl.hp.com>
Date: 04 Apr 1996
From: hajo@quijote.in-berlin.de (Hans-Joachim Zierke)
Newsgroups: rec.bicycles.tech
Subject: Re: rim cracks - advice needed
Jobst Brandt writes:
> Ceramics are insulators, both electrical and thermal, so the braking
> energy converted to heat in the brake pad cannot transfer to the
> aluminum rim where it can be dissipated. The result is rapid pad wear
> and reduced brake effect.
I have noticed this with Shimano pads, and have switched to Sachs/Modolo
pads therefore. These pads do not wear that fast on ceramic coatings. I
think it would need a special brakepad.
> The main benefit was intended to be for wet
> braking, where water lubrication makes soft pads on wet metal rims
> ineffective.
No longer. Magura has a new brakepad that is as good on bare (Mavic)
aluminum. Magura publishes pad/rim performance figures.
> Its resistance to wear is probably also a goal for wet
> conditions that circulate much grit.
That's the main benefit. My several-years-old commuter wheels are as good
as new. I just recommended ceramic coatings to somebody who rides 20.000
kms a year. He has exchanged his rims every year or half year for safety
reasons.
The question is when the rim will get cracks - wether the cracks come late
enough to justify the higher price. I'm sure that ceramic coatings would
pay off on ISO 406 rims used for foul-weather riding, but don't know a
manufacturer who does this.
The recumbent owners have huge problems with rim wear, as soon as they ride
every day.
hajo
--
Niemand übertrifft mich an Bescheidenheit.
Date: 04 Apr 1996
From: hajo@quijote.in-berlin.de (Hans-Joachim Zierke)
Newsgroups: rec.bicycles.tech
Subject: Re: rim cracks - advice needed
Jobst Brandt writes:
> In that respect we should all ride mopeds because pedaling is such a
> chore. I don't see the problem in hearing a faint click when you
> apply the brake. I see no reason to burden the bicyclist with such an
> expense
This isn't always a click, but sometimes it was interval braking. But I
agree that the worst rims weren't manufactured by Mavic. I also don't think
that it must be expensive. If the demand is: "Give us perfect rim joints",
and not: "Give us pretty rims", I don't expect more than 1 or 2 dollar
extra.
> You say that as if you were operating a marginal bicycle shop that got
> stuck with a bad shipment of rims.
Me? Operating a bike shop???
But I know quite a lot of bike shop owners. Building a wheel is labour
cost. If I can build a good wheel considerably faster, it is less labour
costs. With an MA-2, I have to trick around, to avoid spokes at the joint
that are nearly loose, or have exceptionally high tension. With a Reflex
rim, I just tighten the spokes, done.
There is no logical reason, why a "Reflex" in polished condition, and with
less pretty machining, should be considerably more expensive than a MA-2.
Mass manufactured, 2$ should pay it. And with shorter work time, there is
no reason why the customer at the shop should have to pay one cent more for
the wheel.
I know that the current sales policies are different.
> After all, good aluminum rims have been used for 50 years or more
> without machined sidewalls. I still do.
The main reason for all the machined rims was Germany, the new DIN norm. We
now have rather strict requirements for brake performance in the wet. Not
THAT strict - my bikes have easily met the requirements 15 years ago.
For years, manufacturers didn't believe that anodizing gives really bad
brake performance in the wet. Now they couldn't meet safety requirements -
all of a sudden the evil came over them... :-)
Since Germany is worldwide second in market importance for bicycles, the
manufacturers reacted quickly with machined rims.
Sure a polished rim with a good joint works as well. I have no doubt that
the industry salesmen will understand this within the next two or three
years.
hajo
--
Niemand übertrifft mich an Bescheidenheit.
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Frame Fatigue - NOT!!!
Date: 14 Aug 1996 17:16:24 GMT
Clarke Stanley writes:
>> Don't overlook that anodizing is so hard and brittle that it has
>> cracks the first time the aluminum is stressed.
> To say that an anodize coating cracks the FIRST time the aluminum is
> stressed may be presumptive. Whether it cracks or not depends upon the
> stress imposed and strength of the anodize coating.
The anodizing cracks when the spoke sockets are inserted and again
when the spokes are tightened, before the rim is ridden. These cracks
grow under use and propagate into the metal to cause break-outs of
sections around spokes and some have separated circumferentially
through into the hollow of the rim so that the tire remained mounted
on the outer portion that was separate from the inner hoop with
spokes. This is neither presumptive or imagined. Bicycle shops that
maintain high priced bicycles have seen enough of these failures to
know it is not a singular fluke.
I have had sectioned and polished micro-graphs made of MA-2 and MA-40
rims for comparison. The cracks are clearly visible in the hard
anodized MA-40 rim and no cracks are visible in the MA-2.
>> These surface cracks subsequently propagate into the metal and
>> cause failure.
> Again, the propagation of cracks into a substrate material depends
> upon the stress imposed, the frequency, the strength of the material
> and stress concentration of the existing crack or notch.
So? On bicycle rims, the forces are the right kind.
>> This is one hard coat that you didn't want on your bicycle on any
>> structural part.
> How about Vitus frames which have been anodised for many years? They
> seem to hold up very well.
These frames have a cosmetic coating that has negligible effect
because it is so thin that it cannot concentrate stress. In contrast,
rims have such thick coatings that they take substantial time for
braking to wear off the coating. The crazing on these rims is visible
with a magnifying glass when the surface is illuminated at a grazing
angle.
>> For this reason structural aircraft parts are not anodized.
> As a metallurgical engineer with about 40 years aerospace
> experience, I can verify that aerospace aluminum structural parts on
> human rated rocket engines are anodized. If they are not anodized on
> aircraft parts, please tell me more about it, because I'm under the
> impression that aluminum aircraft parts also are anodized, but I
> cannot verify it because I have never worked on aircraft parts.
You may find colored anodized parts but you will not find hard
anodized structural parts because these fail from crack initiation in
the hard crust. Thin protective conversion coatings such as alodine
and cosmetic color anodizing identify parts and protect against
corrosion. Anodizing, as is found on bicycle rims, is structurally
destructive.
There is a large amount of literature on this subject in the industry
and if you are involved in aerospace, then I suggest you look under
anodizing in your technical library. It is all there if you want to
learn about it.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt )
Newsgroups: rec.bicycles.tech
Subject: Re: Rim features that actually works
Date: 26 Aug 1996 19:38:29 GMT
Kristan Roberge writes:
> I don't know the value offhand, but good ol' steel has a better
> thermal conductivity than aluminum.
Oh? That's why aluminum pots and pans have steel handles, so you'll
burn yourself. However, aluminum has about five times the thermal
conductivity of steel. That's why aluminum cooling fins are commonly
used on machinery.
> Steel rims are great when dry. Unfortunately they corrode, and
> terrible when wet, and are heavy.
They don't even work well for brakes because steel rims being such
poor conductors brake worse than hard anodized aluminum. The reason
they are so bad in the wet is that they don't make much heat to dry
off and to boot they are smoother. The micro finish of a material is
dependent on its hardness and steel is harder than aluminum. Chromed
rims are the worst when wet.
> Wood would be a example of a material with a poor
> thermal-conductivity,which is why you don't see wood rims much
> anymore, braking performance quickly degraded as the pads heated up.
Apparently you don't speak from experience. I have ridden down passes
in the Alps with wood rims and can assure you that braking isn't half
bad, however, the pad wear material burns your legs down the hill and
then you put on new pads at the bottom of the Stelvio, for instance.
There are other serious structural reasons for not using wood rims.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: WOOD or Composite Rims?
Date: 16 Aug 1998 02:08:52 GMT
Mike Kallal writes:
> I've seen some wood rims advertised in the "Marketplace." Are these
> New?? Do you think they'd have higher compaction density and/or
> lower void than composite technology? What about resistance to
> lateral torsion? Man, I'd LOVE to have a wheel-set built-up around
> Wood Rims, but I'm not sure I'd know how to glue them up (they sound
> so sophisticated, I presume they're tubular).
Of course they're for tubulars and gluing them is done with regular
tubular glue, except that it works a lot better because the rim never
gets hot from braking and glue sticks to wood better then metal.
However, you can't descend with them worth a damn because the rims
accept no heat and burn off most any brake pad you can find, so much
so that the hot pad material will burn your legs as it ablates. If
you break a rim in a crash, and they often break, you can get a free
piercing, possibly even fatal.
I've ridden plenty of wood. Leave it in the museum.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Plain, Anodized or ceramic coated rims???
Date: 31 Mar 1999 00:16:33 GMT
Razoreye writes anonymously:
> How does chroming the rims affect the brakes..... ETC?
Makes the rim as slick as snot in the rain. This produces the worst
brake surface one can imagine for a bicycle rim. Of course you could
sand blast the aluminum and mat finish chrome it, but that wears
smooth too, after a while.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Plain, Anodized or ceramic coated rims???
Date: 1 Apr 1999 18:34:39 GMT
Ole Blokhus writes:
>> I have never used a ceramic rim, but at the shop we see that they
>> eat through brake pads quickly, and are quite expensive.
> They only eat brake pads when brand new. When the ceramic coating
> has become polished smooth, brake pads tend to last much longer than
> with regular rims. A friend used to go through a set of XTR v-brake
> pads in a couple rides. The next season he got a new bike with
> ceramic rims, and he sold the brakes 6 months later with the
> original pads on them. The conditions were largely the same both
> seasons.
Something seems to be wrong with this picture. Ceramic was intended
to improve wet braking, so it was made rough to penetrate the
lubricating boundary layer of water. For these rims, the cause of
brake pad wear is twofold, abrasive roughness and heat. Braking
converts kinetic energy (motion of the bicycle/rider) to thermal
energy, or heat. The heat is generated in the brake pad by material
deformation, it being the softer of the rubbing pair of materials, and
cannot dissipate as it should by conduction into the aluminum rim that
is insulated by the coating.
Insulating ceramic if smooth, is the worst of both conditions, not
working well when wet, and overheating brake pads when dry. This was
already achieved with hard anodized aluminum rims. What improvement
in braking do smooth ceramic rims promise, and if they are better, why
aren't they made smooth when new? Surface roughness can be controlled
in manufacture of these rims, as expensive as they are.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: MA-3 revisited
Date: 9 Dec 1999 01:00:14 GMT
Alex Wetmore wrote:
> I don't see what good it does to polish up rims on a bicycle.
I assume you mean in manufacture. You must decide how clean you want
to keep your bicycle. A bright polish makes aluminum rims more
corrosion resistant and crack resistant over a brush or extruded
finish. Besides, a polished surface is easier to clean.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Spoke gauge, machined sidewalls and dimples
Date: 16 Jan 2000 00:32:34 GMT
Roger Cantwell writes:
>> Hard anodizing is brittle and will eventually crack the rim.
> Shouldn't that be *may* crack the rim? If it was that definite,
> manufacturers would be stupid to make them at all.
I think eventually is a suitable qualifier. It means if the rim is
ridden with a moderate load. The point is that the rim is already
cracked when you buy it, only that the cracks have not propagated into
the metal yet and reside only in the hard crust.
When this came up years ago, when anodizing was first introduced as a
cost enhancer, I had an MA-2 and an MA-40 anodizing, (other than
anodizing, identical rims), both ridden for more than 1000 miles,
sectioned, polished and micrographed to reveal cracks in the anodized
rim and none in the plain rim. The cracks can be seen even with low
magnification if the anodized surface is illuminated with bright
grazing light.
It's not the manufacturers that are stupid, but rather they take the
customer to be stupid, and as we see their method works. People buy
the stuff and tell others how much stiffer their wheels feel with HARD
anodized rims. In fact, the hard ceramic nature of anodizing means
that the surface must crack before the aluminum begins to carry any
load in bending, the means by which spoke loads are supported.
It's much like colored tires. The same people who were sure that
smooth tires were dangerous are now riding colored tires that are
smooth. It all depends on what the customer thinks is important, and
advertising can convince most people of almost anything... like
saddles with slots down the center like the ones that you can find in
catalogs of 100 years ago.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Velocity Rims-Nipple Problems?
Date: 3 Apr 2000 16:06:00 GMT
Bob Mitke writes:
>> Generally, rims without steel sockets and even more so ones without
>> eyelets, are a bad idea
> Before I disagree, please describe the cases in which it is OK not
> to have eyelets.
Most deep V-section rim have a bed that is strong enough to support
spoke loads, however, it requires good lubrication to prevent galling.
On the other hand, who needs (heavy) deep V-section rims.
>> Meanwhile the bicycle industry, pandering to the whims of the
>> weight watchers who spend inordinate amounts on equipment with
>> functionally inappropriate materials, drops useful and reliable
>> products from the market.
> Get all your friends that agree with you together and submit a nice
> big fat rim order, exactly like you want it (sleeved, pinned,
> etc..). Extrusion die drawings don't go away. If enough people
> agree with you, you won't have any problems convincing a company
> like Sun or Weinmann to run a few thousand rims for you.
As you see, Mavic doesn't give a damn about that. A larger contingent
than I could ever assemble was buying their MA-2 rim when they
discontinued it. Many disbelievers commented here that "they wouldn't
do that" when in fact they had already done so.
> Heck, you could even design your own extrusion profile if you wanted
> to. You would have to pay for tooling, but spread that cost over a
> few thousand rims and the increase in per unit cost is only a couple
> of bucks...
I see you believe everything. It isn't true. Fortunately I have
something to say about IRC smooth black tread (Avocet) tires and that
is why we still have them, in my estimation the best performing tire I
have used. I've used a lot of different tires over the years. If you
think you can influence Continental, your fooling yourself.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Rims, Annodizing
Date: 25 Jul 2000 15:28:51 GMT
Max (?) writes:
>> Machining on rims, in contrast is done to appease bicycle retailers
>> who complained bitterly about brake squeal on new bicycles
> Machining was started to be used to finish the braking surface off
> after welding the seam, not for retailers that don't know how to toe
> in brake shoes properly. It was then caught onto by the marketers.
Rims were smoothly welded for many years before anyone considered
machining them. As I mentioned, Martano tubular rims were extruded
with grooves in the braking surface to achieve the same effect. What
is telling is that new brake pads and new shiny rims squeal no matter
how you toe in the pads. The slick surface of the rim must be worn
off and machining achieves this in two ways, texture and no varnish.
You may have noticed that the finish is like the surface of a vinyl LP
record. That is what prevents brake squeal.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Broken Spoke(s) - Why ?
Date: 5 Aug 2000 22:51:13 GMT
Steve Bailey writes:
> I don't believe the silver Open Pro's were hard anodized. I believe
> the hard anodizing puts a brown coating on the rim, at least that's
> what a 3rd Open Pro that I use has. The Reflex rims were only
> mentioned as to the history of the hubs. No spokes broke on the
> older Reflex BTW.
Even thinner anodizing causes cracking although less than the olive
green dark rims like MA-40's that were the perfect example because
they were identical in all other ways with MA-2 rims that did not
crack. The two rims were from the same extrusion and were identically
manufactured except for the anodizing. As the layer approaches zero
the effect also vanishes because the cracking has such a fine pattern
that it doesn't concentrate stress at any one crack.
Just the same, anodizing is inexcusable on such a highly stressed
aluminum component, one that is naturally beautiful in its most robust
state - polished. Polishing connecting rods in high performance
engines is not idle make-work, it prevents cracks. So what do rim
manufacturers do, the anodize polished rims to give them a head start
on failure and tell the public that it makes the rim stiffer, as if
stiffer were better and achievable with this treatment. Then they
told us they were heat treated which turned out to be another ploy
because the alloy used is not heat treatable.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Broken Spoke(s) - Why ?
Date: 6 Aug 2000 03:12:51 GMT
Mark McMaster writes:
>> So what do rim manufacturers do, the anodize polished rims to give
>> them a head start on failure and tell the public that it makes the
>> rim stiffer, as if stiffer were better and achievable with this
>> treatment. Then they told us they were heat treated which turned
>> out to be another ploy because the alloy used is not heat
>> treatable.
> Many, not all, rims are made of 6000 series aluminiums, which are
> heat treatable. The extrusion temperature of these alloys is above
> the temperature necessary for heat treating, and quenching the
> aluminum after it leaves the extruding die can result in mild amount
> of hardening, of up to a T3 temper. The quenching necessary can be
> done by spraying it with a mist of water as it leaves the extruding
> die, although rim walls are thin enough that they can be air
> quenched (water quenching has the additional advantage of cooling
> the aluminum faster, making it easier to handle and increasing
> material through-put).
> The extrusions could be further heat treated to a higher temper with
> additional processing, although I do not know if any rim
> manufacturer does this.
> So, with some rim alloys, a manufacturer's claim of heat treating is
> not entirely incorrect, even without post extrusion processing.
So all that said and done, why do these rims crack when we had ridden
silver shiny rims without a crack for as long as they had aluminum
rims since switching from wooden ones. It was the advent of the dark
anodized rims that heat treatment became a promotional issue, the
same time when rims began to break up, some separating through the
circumference of the hollow section so the tire was on the outer one
and the spokes on the inner one. We've come back from that extreme
but not far.
I recall that when these claims were first made, several of these rims
were found to not be heat treatable by users who had access to
analysis labs. I went to the trouble of getting an MA-2 and MA-40
sectioned and polished to make micrographs of their crack propagation.
As if there was any doubt. Both rims had a couple of thousand miles
on them and of course the MA-2 had no cracks while the anodized
surface of the MA-40 was full of them, some of which had advanced deep
into the metal.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: How to know when to replace rim?
Date: 18 Aug 2000 16:41:23 GMT
Jeffrey L. Bell writes:
> Just out of curiosity I measured the wall thickness on the section
> that broke loose.
> It was in the range .9 to 1.0mm, except for one spot that had a
> funny tear in it that was less than .8mm. This thin spot was at the
> joint in the welded and machined rim.
> Metalurgically, is there anything in the grain of the surface that
> would tell me where the failure started?
If it broke with that thick a wall it must have been an anodized rim
with crack propagation from the anodizing. Anodizing on the tensile
side, the inside of the sidewall is where cracks develop the best even
though the outside is worn free of the crust.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: How to know when to replace rim?
Date: 19 Aug 2000 22:21:31 GMT
Tom Thompson writes:
>> If it broke with that thick a wall it must have been an anodized
>> rim with crack propagation from the anodizing. Anodizing on the
>> tensile side, the inside of the sidewall is where cracks develop
>> the best even though the outside is worn free of the crust.
> So, one cannot even see the cracks unless the tire is removed and
> the rim then inspected from the inside? Jeez, that's a little scary
> - and all the reason I need to stay away from anodized rims.
It's worse than that. Because most of our wreck.bike folks like to
buy the latest rave rim, tire, frame, wheel, etc, especially if it's
counter to good sense, the reliable standard equipment is no longer
available. A rim that isn't anodized, welded and machined is a
scarce object. As you see the most durable best all around rim, the
MA-2 was discontinued by Mavic, the largest rim supplier. That's
spooky.
This has been getting worse at a rapid rate. First plain functional
rims disappeared, then 32 and 36 spoke road rims vanish and all you
can get are $40-$50 rims.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Rim Wear Question
Date: 18 Aug 2000 22:24:37 GMT
anonymous snipes:
> Put the edge of a ruler across the braking surface and estimate the
> size of the gap. If it's about 2mm you should start thinking about a
> new rim. If it's 2.5mm or more, replace it before your next ride.
I see we are getting some more hypothetical advice that is dead wrong.
Wall thickness in most rims is around 1.5mm. Your advice serves only to
show that you don't do this.
> The 217 is only slightly less soft than an medium-priced French
> Brie. I once burned through one in 3 months, all on a 6 mile a day
> commute. I highly recommend an upgrade to Mavic's 517 SUP.
Oh how cute. Brie! You think that Mavic has special soft alloys for
some of their rims. It's hard enough to get one that extrudes well
and is durable enough not to fracture. Their anodizing is what causes
most of their failures, not the hardness of the alloy. SUP is
gratuitous machining on the sidewalls that makes the wall thickness
undefined. The purpose of this is to prevent brake squeal on new
bicycles, nothing else.
On their web site Mavic lathers the reader with the following BS:
SUP
Concept :
- After bending, the rim joint is arc welded. The welded seam is then
milled by digitally controlled machines.
Yes, and to what end. Aluminum rims have been in use for more than 40
years without welds with no problems.
Benefits :
- On a SUP rim, the resistance of the joint can increase to 90 %. On
ordinary sleeve-joint rims, resistance at the joint is 40 % to 60 %
lower than on the rest of the rim
Resistance of the rim joint to WHAT? The rim joint is entirely a
compression joint that never sees tension. If the alignment spud
fits closely, and they do or you could pull them apart, then this is
specious at best. This kind of BS is what feeds the masses.
- No visible joints that could cause shuddering during braking.
As I said, we've been riding butt jointed rims for a long time and no
brand named rim has presented any functional discontinuity at the
joint... but they would lead you to believe so.
- The "monobloc" geometry makes wheel building and balancing easier.
Easier for whom? I assure you that this is based on myth and as they
say "whole cloth". However, if you look on the Mavic web page:
http://www.mavic.com/eng/tech/techno.htm
You'll find a whole assortment of these techno buzz words, none with
any merit.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tight fitting tires needed
Date: 30 Aug 2000 14:25:30 GMT
Mark Perry Ruebay writes:
> Recently I purchased a hybrid bike to use as a commuter. When I went
> to change tires from the stock to something closer to a 32c I found
> that I couldn't make any of them stay on the rim very well. I've
> tried some wire beaded and some Kevlar beaded but if I come anywhere
> close to the minimum recommended inflations for the respective tires I
> usually end up with the tire popping off the rim and me frantically
> deflating the tube before it bursts.
You failed to give the most important information, and that is, what
rim are you using? What may not be apparent is that the tires we ride
are in act clinchers that stay on the rim primarily by the clinch of
the hooked sidewall that retains the tire bead. To test this, I cut
the bead wire in five places (on a tire that was worn out) and mounted
it on an Mavic MA-2 rim where it stayed in place while inflating it to
100 psi.
I suspect you have a straight sidewall rim, good only for low pressure.
No tightness of tire will help you much there. Get some better rims.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tight fitting tires needed - blow off test results
Date: 31 Aug 2000 17:12:33 GMT
Mark McMaster writes:
>> You failed to give the most important information, and that is,
>> what rim are you using? What may not be apparent is that the tires
>> we ride are in act clinchers that stay on the rim primarily by the
>> clinch of the hooked sidewall that retains the tire bead. To test
>> this, I cut the bead wire in five places (on a tire that was worn
>> out) and mounted it on an Mavic MA-2 rim where it stayed in place
>> while inflating it to 100 psi.
> In either of these tests, was the tire with the cut bead ridden any
> distance, to verify that the bead stayed clinched as the tire
> sidewall flexed under load?
I won't try that because the tire is about to explode anyway, the
cords having been cut where the bead wire was cut. The point of the
experiment is to demonstrate that the clinch is the active part of
this. The whole subject came to my interest when I first heard about
tire blow-offs of steel bead tires from braking heat. I was also
aware that wire beads did not keep tires on straight wall rims at
less than half the suggested inflation pressure. When folding tires
came along, I noticed that they looked much like ancient clinchers
that had no structural bead girth and discovered they could be
stretched to be larger than the rim just like ancient clinchers. The
wire cutter experiment was done to convince a colleague that these
were in fact clinchers all along and that the restrictive bead length
of folding tires was gaining little to nothing for retention.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Wheel deflection (rebuilt wheel rubs pads)
Date: 12 Sep 2000 19:56:25 GMT
Andy B M? writes:
> The dish is correct, but the brakes were slightly off center. And
> yes, the new rim is still quite loud when braking, so the old wheel
> may have rubbed silently. And the rim is an old MA-2, so no
> machining. And it is taking too long to wear them in and get them
> to shut up. They are quite loud right now, although they quiet down
> after about 30 miles. But then loud again for the next ride.
I don't understand what 30 miles of riding can do that would gradually
quiet the brakes, unless it is mostly down hill with braking. The
problem is one of wearing off the glaze on the rim and brake pads that
can either be from manufacture or from oil contamination since then.
This effect is best fixed by either riding through a long mud puddle
with the brakes, on or wetting the rim with soap and putting household
cleanser in the rim-to-brake interface and riding that with the brake
on. If more people, and bicycle shops in particular, had done this,
we wouldn't have to bear the expense of machined rims today.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: ?Fix Ceramic Coating?
Date: 13 Oct 2000 20:21:59 GMT
Andrew Kalter writes:
> Does anyone know how to fix/repair chips on the ceramic coating on a
> set of rims. I have Mavic Crossmax wheels which have taken a lot of
> abuse which has resulted in chips in the ceramic. This causes the
> braking to become very uneven.
> Is there any aftermarket coating I can use to fill in the ships to
> smooth out my braking?
If there was one, the rim makers wouldn't go to the trouble of baking
a ceramic coating onto the rim. Ceramic coat is hard and that also
makes it brittle.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: MA2 Replacement
Date: 20 Oct 2000 01:05:38 GMT
Michal Knudsen writes:
>>>> Check the internal shape of the extrusion. The MA-3 isn't even
>>>> remotely related to the shape of the MA-2.
>>> Talked with Eric at Mavic today. Turns out that indeed they did
>>> use the MA-2 die as I have previously stated. The old MA-40 die
>>> was also used for the MA-3 rim.
>> Let me echo that the MA-3 has nothing to do with either of those
>> rims in cross section, size, configuration or otherwise. One is a
>> single hollow section rim and the other a rim with three chambers
>> of two alignment pin holes and a main chamber. I don't know where
>> you get this.
> I confirmed the worst on the phone today with Mavic. They made
> entirely new dies for the MA-3 rim. Why, then would they have just
> not made more MA-2 dies? Must be because something has become
> burdensome in the MA-2 production. Why else would they go through
> the trouble of making a 500+gram, machined rim, if the MA-2 was
> easier and in more demand?
What you mean WE white man... burdensome my ass. They just decided
that they would concentrate on boutique rims from now on. It's not
like the MA-2 was not selling. They could have jacked up the price
but I believe there are new folks at the helm who have no idea what
the MA-2 was good for and why people preferred it over other rims.
The decision makers are not always technically adept. These seem to
be the opposite but marketing makes up for their failings. You see
people flock to their Helium and Ksyrium rims that are named after who
knows what, but it sounds good.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: MA2 Replacement
Date: 18 Oct 2000 16:48:18 GMT
Michal Knudsen writes:
>> by any chance, did you ask eric about producing the MA-2's again?
> I didn't Tom. They are a very hard rim to make. Parallel sidewalls
> are hard to roll exactly, polishing has become a burden, plus
> mistakes can't be machined over or anodized in a lot of cases. They
> became too expensive to produce at their price point. I have a few
> pairs of NOS 36 hole MA-2s left though if you are looking, Mike.
How come is it that these excuses for Mavic are so free flowing from
rim people when they don't make any sense? It really challenges
credibility. The MA-2 cost half what alternatives cost. They were
not flat sided nor anodized, machined or welded, all processes that
cost more. To say they were hard to make is ludiocrous. All rims in
the past had similarly curved cross sections and made good closure at
the joint, be that Fiamme, Ambrosio, Nisi, Martano, Super Champion,
Weinmann, Scheeren, or even Mavic. We were not all born yesterday.
Polishing has becone a burden... give me a break!
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: "3-cavity cross section design ... more effectively than double
eyelets"
Date: 9 Nov 2000 21:05:11 GMT
Jon Isaacs writes:
> Rim designs are complicated and a compromise between weight,
> difficulty of manufacture and strength/durability. The question is
> not how to build the strongest rim, that is rather easy, just make
> it solid. The question is how to distribute a minimal amount of
> material in the most reasonable way that is manufactureable.
You make it sound so difficult. The ideal all around rim was
developed long ago and was made by many manufacturers for tubulars.
In fact there wasn't much difference between rims 30 years ago except
finish... how the sockets and eyelets were inserted and the manner of
closing the rim joint. Good clincher rims, similarly emulated that
shape and did so for many years, the MA-2 being the last survivor of
that era.
What we see now are marketing ploys surrounded by vague claims of
functional superiority, unsupported by reasonable proof or technical
logic. None of the extruded cross sections are "hard to make".
Looking at electronic heat sink extrusions can give an idea of how
complex an extrusion is easily made. Although some defenders of the
industry claim that welding and machining is needed to satisfy today's
market, I have a stack of rims on which you cannot find the rim joint
in the brake contact zone, blindfolded.
> To make this compromise is not an easy task and requires more than a
> bit of analysis (and testing) that is probably beyond the scope of
> some "rants" on a web site.
Bending of beams is well understood as is the practical aspect of rims
and how the tire attaches to it. I don't know what scope you imagine
but it isn't there. We have computer modeling applications that can
optimize these cross sections with ease. It may seem obscure to people
not in the field but it isn't.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: rim strength
Date: 28 Nov 2000 17:26:32 GMT
David L. Johnson writes:
> The answer to the original question was more obvious back in the
> good 'ol days. Anyone who had a set of Scheeren Weltmeister rims
> would know that the built wheel is much stronger than the rim.
> Those rims were extremely weak on their own, being little more than
> a thin cylinder of aluminum compressed into a more-or-less box
> section, held in place by balsa-wood (really) blocks at each spoke
> hole.
These were interesting rims in that the designer seemed to realize
that rim cross section was weakest at the nipple holes and that much
of the weight of most rims was wasted because all the wall thickness
was mainly chosen to bridge these holes. For a tubular tire track or
TT rim, where braking is not important, a thin walled rim could be
made with little material loss at the spoke locations. The Scheeren
achieved double wall support for spoke loads by using hardwood
separator blocks locally inside the rim at nipple holes and by
dimpling the rim bed just enough to accept the nipple head that rose
slightly above the rim bed, could get by with a hole only as large as
the nipple shaft, angle drilled through the rim. These rims probably
had the best strength to weight ratio for any rim made.
Jobst Brandt <jbrandt@hpl.hp.com>
From: jobst.brandt@stanfordalumni.org
Subject: Re: Rolf Sestriere Wheels
Newsgroups: rec.bicycles.tech
Date: Fri, 07 Sep 2001 16:27:04 GMT
Paul Southworth writes:
>> As was pointed out, the Rolf patent is invalid because the paired
>> spoke arragement it describes was already in use in 1870 as was
>> shown in pictures of antique bicycles:
>>http://www.meuseummercantile.com/antique_bicycle.htm
> That doesn't seem like a valid URL. meuseummercantile.com is
> not a registered domain name.
Make that:
http://www.inkgroup.com.au/calendar/photography/bicycle/int.html
As Mark McMaster offered earlier on this subject, the bicycle in the
second row, third picture has paired spokes. I guess it got garbled
when I saved the URL.
Jobst Brandt <jobst.brandt@stanfordalumni.org>
From: jobst.brandt@stanfordalumni.org
Subject: Re: Rolf Sestriere Wheels
Newsgroups: rec.bicycles.tech
Date: Fri, 07 Sep 2001 22:14:03 GMT
Jay W. Beattie <jbeattie@lindsayhart.com> writes:
>> http://www.inkgroup.com.au/calendar/photography/bicycle/int.html
>> As Mark McMaster offered earlier on this subject, the bicycle in the
>> second row, third picture has paired spokes. I guess it got garbled
>> when I saved the URL.
> I haven't been reading the NG and missed Mark's post. Has the
> patent been ruled invalid, or is someone just claiming that it
> incorporates known, but undisclosed prior art?
The patent examiner obviously didn't dig deep enough... it's only a
bicycle. The prior art unambiguously invalidates the patent whether
there has been a ruling on it or not. If challenged, I doubt that
Rolf will attempt to defend it. That's why anyone can build such
wheels without royalties.
Jobst Brandt <jobst.brandt@stanfordalumni.org>
From: jobst.brandt@stanfordalumni.org
Subject: Re: Snaping Spokes
Newsgroups: rec.bicycles.racing,rec.bicycles.tech
Date: Sun, 23 Sep 2001 23:53:11 GMT
Chris Reeder writes:
>> I can only go by what Mavic says:
>> http://www.mavic.com/eng/prod/fiche/rim/r_openp.htm
>> That's a lot of welding, anodizing and machining if their web site is
> What's the problem with machining? you're going to machine it
> anyway every time you grab the brakes.
My brakes act as a tracer lathe and take off the same amount around
the rim that has a known wall thickness. Machined rims have an
unknown and variable wall thickness, all at the users expense. I
prefer to do my own rim wear rather than a pre worn rim from the
manufacturer. All the BS of why we need machining is a blatant dodge.
Rims can be made to have an undetectable joint and have been made that
way for more than 50 years. I have a new MA-2 rims that have no
detectable mismatch at the rim although this is the excuse given for
machining Mavic (and other) rims today.
I suspect the reason for machining rims is to prevent brake squeal on
new bicycles. Machining is done with a pointed tool that leaves a
vinyl LP like surface. This effectively suppresses brake squeal.
Jobst Brandt <jobst.brandt@stanfordalumni.org>
From: jobst.brandt@stanfordalumni.org
Subject: Re: vintage lightweight wheelbuilding
Newsgroups: rec.bicycles.tech
Date: Thu, 15 Nov 2001 16:37:47 GMT
Mike Lee writes:
> I'm contemplating building a 3X, 36 hole wheel using Superchampion
> Medaille d'Or rims. These rims are 270 grams and maybe too light
> for street use(I would be selective where to ride though). Has
> anyone built wheels using rims this light for general use and if
> they did how did it all work out? I'm bout 180 lbs which probably
> doesn't make me a lightweight.
Beware, these rims cannot take much tension before they warp into a
potato chip. Stress relieve early to protect yourself against rim
damage. This is the rim on which I learned about the limit of
tension. Shortly after that experience, a friend went on a ride with
me with a newly built rear wheel with which we climbed steep hills
with no problem, however, when braking into the first curve on the
descent, his wheel went into a big wobble. This was understandable
for a wheel at the tension limit. Tension in the rear half of the
wheel rises on braking and can exceed the buckling compression of the
rim. Fortunately, judicious reduction of tension on some spokes got
things back in order.
These were favorite criterium wheels in the days of tubulars. Ride
them but inflate your tires hard or you'll put a ding in the rim the
first time it bottoms!
Jobst Brandt <jobst.brandt@stanfordalumni.org>
From: jobst.brandt@stanfordalumni.org
Subject: Re: New Bontrager Road Wheels?
Newsgroups: rec.bicycles.tech
Message-ID: <wf528.10783$TI3.99492@typhoon.sonic.net>
Date: Sat, 19 Jan 2002 02:56:28 GMT
Benjamin Weiner writes:
> On the subject of wheels, I don't really care what anyone else
> chooses to ride, but clearly if flashy wheels displaced ordinary
> ones and made it impossible to find e.g. reasonable rims that would
> be regrettable. OTOH, don't Bontrager themselves make sensible
> rims?
What you mean "if"? The Mavic MA-2 and its siblings have been
discontinued, leaving only inferior models in their place. The
non-welded, non-anodized, and rims with sockets and eyelets are gone.
Meanwhile, most of the high demand rims cannot be readily built
without special equipment, tension being more than spoke twist will
resist. I see an effort by manufacturers to stop the home built wheel
trend.
They're doing a good job, whether intentional or not.
Jobst Brandt <jobst.brandt@stanfordalumni.org> Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: New Bontrager Road Wheels?
Newsgroups: rec.bicycles.tech
Message-ID: <bWn28.10993$TI3.102219@typhoon.sonic.net>
Date: Sun, 20 Jan 2002 00:10:47 GMT
Mike Jacoubowsky writes:
>> I see an effort by manufacturers to stop the home built wheel
>> trend.
> OK, I'll bite. What's the "home built wheel trend" all about? When
> did it start? Better yet, who are the forces trying to stop it?
> Did it really get so large as to become a threat to either the
> standard or boutique wheel market? Can we point to anything in
> particular that indicates an industry in collusion against THE
> PEOPLE? (Why is the movie "Meet John Doe" coming to mind?)
Not at all against "the people" but headed opposite to do-it-yourself
consumers. 16-spoke wheels cannot reasonably be built except with
tools and fixturing that riders don't have. Even if they did, they
couldn't do a roadside repair as I have often enough for bent wheels
from a fall or collision. It's like the BMW 7-series that recently
stopped on the road for no reason other than an electronic failure
that cannot be repaired other than replacing the module.
> Every day I leave the shop, wiping my brow, thinking, whew, got
> through another day... sure is tough though, now that everyone's
> building their own wheels! What will I do to pay the bills? (The
> truth? The more people work on their own bikes, the more hooked on
> cycling they'll become, and they'll more likely get additional
> people into it. Doesn't matter whether it's overhauling a bottom
> bracket, adjusting a derailleur, fixing a flat or building a wheel.
> It's GOOD for business, not bad).
The point is that working on ones own bicycle becomes progressively
more difficult with things like 16-spoke wheels or cartridge BB
spindles that defy repair. Both of these things can fail and need
work, work that may be out of the rider's capabilities.
> You talk of your favorite rims being discontinued, as if Mavic made
> an intentional decision to discontinue a great product in favor of
> lesser ones. Why would anyone in their right mind intentionally do
> such a thing?
That's a good question. Judging from stock on hand in most bicycle
shops here and in Europe, this was a hot selling item. The reason for
discontinuing them seems to come from the OEM market which is probably
much larger than the after market. Since fashion is what sells new
bicycles, there was no room for a utilitarian rim like the MA-2. That
still doesn't explain the existence of the MA-3, a looser in
comparison.
> Isn't it more likely that we're looking at a normal product
> evolution, and (from your standpoint) seeing things at a low ebb at
> the moment, but sooner or later things will get better? Kind of
> like the way Detroit built a whole lot of loser cars for awhile
> before getting their act together and building (relatively) decent
> stuff again?
They haven't and they don't. It's all like "Roger and me", the movie
about what killed GM and is going on at Ford, Chrysler already having
capitulated. We have a bunch of business types running technical
companies of which they understand little. Marketing is important but
long term technical development makes marketing possible. My model of
this, be that GM or HP, is that only the output is scrutinized without
an understanding of where that output arises. It's like observing a
black box with an output shaft that turns, wiggles and pumps in a
complex motion. There is no way of estimating what the mechanism is,
however, shown the mechanism, the output can readily be determined.
> Of course, Mavic's not the only manufacturer of rims either, and
> there are at least a few left that don't also make high-end prebuilt
> wheels. If the demand is there for an MA-2 equivalent, wouldn't you
> expect one of those companies to build one?
As I said, aftermarket is not an interesting field.
> PS: Perhaps someone should market a "home built wheel" package? It could
> have your book, a pair of rims, and spokes of appropriate length for a set
> of small flange 32-spoke rims. Seriously. It could possibly include
> something like a Heathkit-style manual for the actual assembly. Perhaps
> when you retire from HP, it's something you might want to consider.
Sounds like a Phil Wood enterprise, something that doesn't appeal to
me. Thanks for the suggestion. I don't want to get into the fickle
bicycle industry.
Jobst Brandt <jobst.brandt@stanfordalumni.org> Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: Rim Cracks
Newsgroups: rec.bicycles.tech
Message-ID: <qZTp8.11842$44.73298@typhoon.sonic.net>
Date: Mon, 01 Apr 2002 07:27:18 GMT
John Carrier writes:
> Just finished a major tune-up on my bike and while installing a new
> tire and cleaning up the rim I discovered cracks radiating from a
> couple spoke holes on the rear rim. Both are from drive side
> (highest tension) spokes. 1800 miles on the rim.
Anodizing puts a ceramic crust on the aluminum and because it is so
much harder than aluminum. It takes all the load of any stress on the
rim and cracks before the aluminum carries any load. These cracks are
visible on a new wheel when inspected under grazing light with
magnification. That anodizing causes structural failure is well
understood in the aircraft industry but, as usual, the bicycle
industry is immune to cross contamination from sources outside their
own shop.
Early on, I had a used Mavic MA-40 and an MA-2 sectioned, polished and
photographed in the metallurgy lap at Alcan Aluminum that showed
anodizing cracks propagating into the aluminum while the MA-2 had no
cracks.
> Rims are Mavic Reflex Tubular. I recall reading about similar
> problems with the Reflex Clinchers (now replaced with the Open Pro).
> Has anyone had a similar experience with the tubular rim?
Unless there is a major revolt (and even then with minimal
probability) there will be no improvement in this department. There
is NO reason to anodize, weld or machine rims, all price increasing
features, that do the rider no good. Machining absolves the bicycle
shop from squealing brakes on a show room bicycle, a feature that
wears of in the first few brake application in wet weather.
Fashion being what it is to most bicyclists, we won't even hear an
audible response to this situation, just as we haven't since I first
wrote on this subject years ago. In fact, after I wrote about it, I
got the impression that Mavic stopped making the MA-2 (their best all
around rim) that I touted, in retribution for my negative comments.
> Obviously, I'll have to replace the rim... it's going to fail. Is
> the failure mode catastrophic (One moment you're riding, the next
> you're sliding down the pavement)?
Yes? And with what? There isn't much choice today although some rims
are silver anodized which is no better. Besides they are welded and
mostly machined.
Jobst Brandt <jobst.brandt@stanfordalumni.org> Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: Rim Cracks
Newsgroups: rec.bicycles.tech
Message-ID: <vXsq8.12362$44.76974@typhoon.sonic.net>
Date: Wed, 03 Apr 2002 01:31:07 GMT
Craig Brozefsky writes:
>> The cracks are hairline, and the wheel is on my
>> townie/beater/commuter, so I won't replace it until the sidewall or
>> an eyelet gives out, and then probably with an MA-3, which is what
>> I used to replace a 32h MA40 last year when an eyelet did pull out.
>> That rim had 6000-7000 miles on it. I did some light loaded
>> touring on the MA-2, and for much of it's life I weighed in excess
>> of 200lbs. I'm now down to low 190s, so maybe I will get more
>> mileage out of my wheels.
All cracks are "hairline" until separation, so that is no consolation.
My pedal cranks that broke also had hairline cracks until they failed.
That is why I inspected them for (hairline) cracks under sunlight at
various angles.
> I have some MA-3s with hairline cracks around one or two eyelets.
> The rear has two eyelets with hairline cracks and is 36H and
> slightly out of true (haven't trued it up since it's just barely
> off). The front is 32h and has one one crack I could see. I was
> using bright overhead lights at an angle, not direct beams like a
> flashlight so perhaps there is a better detection method. On that
> note, any tips on detecting and gauging metal fatigue in various
> materials with common household items would be welcome, books
> included. I could use some tips or pointers on evaluating and
> dealing with steel frames too. Is there perhaps a "Metallurgy for
> the Home Wrench" text? Jobst, does your book cover this topic or
> have pointers to materials on it?
We rarely had rim failures before the low spoke count/anodized craze
began. Therefore, no one worried about these things. There were rims
with eyelets only and no socket to distribute load to the other wall
of the rim, but then no one who rode much used them. The MA-3 is such
a turkey but to underscore that, it is anodized.
> I am not planning on replacing these until there is a more definite
> failure, barring some evidence that there is a likely chance of a
> disastrous failure mode (front wheel collapsing) indicated by cracks
> in the anodizing. Is there a way to gauge the cracks? It seems
> like this bit of triage will be more necessary when we can't buy
> non-anodized rims anymore.
I don't know what users can do to motivate rim companies to produce a
reasonable and useful product. I have given up.
> This is on my fixed city bike and I am quite dependent upon it and
> spend a good deal of time on it each day.
I bought a small cache of MA-2's when it was almost too late. I would
have bought more had I known how fast they would vanish. It was the
most popular rim here and in Europe where nearly every bicycle shop
had them in stock. In Linz Austria, my friend had a wheel failure and
we just went into the bicycle shop, bought a new MA-2 and on our way
again. I saw these rims everywhere I went.
Jobst Brandt <jobst.brandt@stanfordalumni.org> Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: aero rims stronger?
Newsgroups: rec.bicycles.tech
Message-ID: <7Xgx8.19860$44.126202@typhoon.sonic.net>
Date: Tue, 23 Apr 2002 17:34:59 GMT
Brian Plaugher writes:
>> Why do you want a stronger rim?
> What I want is a durable wheel. My CXP-30s have 36 spokes, not the
> fewer number or non-standard spokes seen these days. I am building
> up a second bike, and have the option of getting some CXP33s (32
> spoke). My sole interest in aero rims is for overall wheel
> durability. My question, rephrased: to what extent do aero rims add
> to the durability of a wheel?
None. If the tire bottoms on a road hazard it will generally dent the
bead of the rim, which is no stronger on a deep sectioned rim than on
others. Sidewall wear is also the same, sidewalls being much the same
across the field of rims, although machined rims may be slightly
thinner locally. As far as load carrying, the old socket and eyelet
Mavic MA-2 was, in my estimation, the best all around rim. I don't
have loose spokes and the rims remain true through many 1000 miles,
usually failing from worn out sidewalls, but also from dings in the
bead. I have a collection of these in my garage.
Jobst Brandt <jobst.brandt@stanfordalumni.org> Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: gritty road brakes
Newsgroups: rec.bicycles.tech
Message-ID: <Dsl_a.11269$dk4.430667@typhoon.sonic.net>
Date: Wed, 13 Aug 2003 07:07:15 GMT
Terry Morse writes:
>> And for the record, I've read substantial verbiage on this group to
>> the effect that anodizing causes fatigue. In rim applications this
>> is almost never the case from all the examples I've seen.
It's good you add "from all the examples I've seen" because materials
literature is full of description of such failures. Back in the days
of the MA-2 I sent a well used MA-2 and a G-40 to the metallurgical
lab at ALCAN to a bikie and tribologist who ran them through
micro-inspection of cut and polished cross sections. As expected, the
MA-2 had no cracks while the G-40 had a crazed surface and several
large cracks that were initiated by its brittle hardcoat.
>> In extreme cases, cracked anodizing /can/ be a fatigue initiator,
>> but this is not seen often in the kind off applications we're
>> talking about here.
What do you call "extreme cases", in the early days of anodizing at
Mavic we had daily reports of cracked rims here on wreck.bike. Fresh
out of the crate these MA-40 rims displayed crazed surfaces when
illuminated by bright grazing incidence light. I suspect that is
because the extrusions were anodized before forming hoops.
>> All kinds of fatigue-loaded components in planes, cars, motorcycles
>> and bicycles are anodized for corrosion resistance very
>> successfully with no adverse affects. One notable example has to
>> be suspension forks. Both bicycle and motorcycle forks use [hard]
>> anodized stanchions for improved friction properties, corrosion and
>> wear resistance, and I've yet to see fatigue resulting from the
>> anodizing alone - it's always been initiated by stone strike damage
>> or some other flaw.
You picked the wrong application. These elements are built for
rigidity and do not sustain high stress. Rims flex continually in use
and sustain high bending stresses, ones that effect the "outer fibers"
from the axis of bend greatest. On top of that there are stress
concentrations and residual stress in the rim around spoke holes. It
is the aircraft industry that has the most to say about the hazards of
anodizing that acts as a natural crack initiator and must be avoided
for any high stress applications.
What makes you such a defender of poor engineering and manufacture?
What do you get out of this?
> Hard (Type III sulfuric acid 0.0023") anodizing reduces the fatigue
> life of Al alloys by about 60%. You can find references to this
> number in the literature. Hard anodizing is only appropriate for
> thick, lowly stressed members. Rims don't qualify for hard anodizing
> on either count.
> terry morse
I'm glad to see that others can see past the false promotional claims
of such manufacturers. Unfortunately many people identify with their
purchase so completely that finding fault with it becomes equivalent
to self criticism... I am my bicycle, my bicycle is me. I was smart
enough to buy it. It must be good.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: gritty road brakes
Newsgroups: rec.bicycles.tech
Message-ID: <9%x_a.11466$dk4.433979@typhoon.sonic.net>
Date: Wed, 13 Aug 2003 21:23:17 GMT
Jim Beam writes:
>> It's good you add "from all the examples I've seen" because
>> materials literature is full of description of such failures. Back
>> in the days of the MA-2 I sent a well used MA-2 and a G-40 to the
>> metallurgical lab at ALCAN to a bikie and tribologist who ran them
>> through micro-inspection of cut and polished cross sections. As
>> expected, the MA-2 had no cracks while the G-40 had a crazed
>> surface and several large cracks that were initiated by its brittle
>> hardcoat.
> Jobst, Mavic don't make the ma40 any more. isn't it time you also moved on?
So what! The point is that identical extrusions, (and I don't recall
whether it was a G-40 or MA-40) one polished, the other anodized
demonstrated the effect described in metallurgical journals about
anodizing, a brittle surface coating developed in/on the parent metal.
> 1. Last time you talked about your "ALCAN" friend you said it was
> dye penetrant testing. That would not reveal extrusion flaws in the
> microstructure. It's a little disturbing to see you subtly massage
> your story to suit your argument.
Yes? So what is not to your liking? Dye makes cracks visible in the
cut and polished cross sections. What "disturbs" you about that?
Besides, this is all old hat.
> Are you going to post the pics so we can all see what you really
> did?
I filed those away and would have to search for their location.
That's pretty old stuff.
> 2. MA-2 was also available in anodized. I have one to prove it.
> you never differentiate between Ma-2 "bright" and MA-2 silver
> anodized. Presumably neither cracked for you.
The anodized version was called an MA-40 or G-40. I have never seen a
black MA-2.
> 3. A fork is a low-stress application??? You care to step outside and
> debate that some time big boy? I've never heard such a crock.
That is so because a fork failure usually leads to serious injury. If
ridden in rain, rims wear out before developing fatigue cracks and
only since rims were anodized did a large number of rims have sections
pull out at individual spokes. Some rims without double wall sockets
even cracked circumferentially so that the tire remained mounted on
the outer part that was no linger connected to the bed.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: Ksyrium rim cracks
Newsgroups: rec.bicycles.tech
Message-ID: <8uz_a.11497$dk4.434389@typhoon.sonic.net>
Date: Wed, 13 Aug 2003 23:04:36 GMT
Tom Nakashima writes:
> I just spoke with the plating shop here at the Stanford Linear
> Accelerator Center, they said they've never seen cracks in the
> anodizing. We're going to run a test on .062" aluminum, have it
> black anodized then bend it to see if cracks occur. Any suggestions
> for other test, we also have a Rockwell hardness tester here.
I think you'll need to specify depth and "hard anodized" to make a
valid comparison. Cosmetic anodizing can be made thin enough that it
has essentially no effect on cracking much like the light pink rims
from Mavic.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: Ksyrium rim cracks
Newsgroups: rec.bicycles.tech
Message-ID: <sEy_a.11483$dk4.434224@typhoon.sonic.net>
Date: Wed, 13 Aug 2003 22:07:20 GMT
Tom Nakashima writes:
>>> Are these cranks in the rim itself, or the anodizing? I've gone
>>> through quite a few Mavic MA-2's, and Open 4s, never seen a rim
>>> crack from just riding or hard braking.
>> If the cracks are visible, they are in the metal, regardless of
>> anodizing. The MA-2 may not have cracked but had you used the
>> identical rim with black anodizing, you would most likely had
>> cracks. That rim would have been a MAVIC G-40 rim.
> A little confused now, I know you said "most likely" and "may not
> have cracked." Mavic made two similar rims, the MA-2 and the G-40,
> only the G-40 is black anodized and has more potential to crack? So
> it is the anodizing which weakens the rim? If you can lead me to an
> FAQ or literature on this I would love to read it.. Just curious,
> what happens when the rims crack? Can they collapse at anytime?
Crack generation is not a sudden event but a fatigue failure that take
many thousands of stress cycles (loaded wheel rotations) to develop.
The cracks are especially easy to see on dark anodized rims and it is
the crazed surface of the anodizing that initiates crack development.
It is much like bending the knee having a scab. The hard, inelastic
scab cracks and tears the redeveloping skin beneath, causing bleeding.
In contrast, after soaking the scab in water it can often be removed
and the knee bent without tearing the skin.
Anodizing is a hard and brittle ceramic coat that already is crazed
from rolling the rim into a hoop. Additional (mostly invisible)
cracking occurs when sockets and eyelets are riveted into place.
These cracks can often be seen by strong illumination in a grazing
incidence. The thicker the anodizing, the greater the initial crack
size.
http://aerade.cranfield.ac.uk/subject-listing/esdu/ES104.html
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: The Book, The Wheel, No Taco
Newsgroups: rec.bicycles.tech
Message-ID: <Vuu0b.12966$dk4.479947@typhoon.sonic.net>
Date: Tue, 19 Aug 2003 19:02:13 GMT
Martyn Aldis <martyn.aldis@syntagma.co.uk> writes:
>>> that would be true in the absence of other defects. but as you can
>>> see in this pic,
http://technology.open.ac.uk/materials/mem/images/images_cc/ccf3.gif
>> Your picture is of a machined sidewall, not an extruded form. The
>> profile was anodized in the extruded bar condition and is anodized
>> inside and out. When forming the hoop, the anodized surface crazes
>> being less elastic than the aluminum substrate that is yielding
>> about
> I'm interested to know how you can tell that the process took place
> before the hoop was formed in this case. On rims with welded joints
> it looks like the weld is made and tidied up before the surface
> finishing process.
You're right, welded joint rims are anodized after forming. I was
thinking of the butt-joint-with-filler-piece rims that were formed
after anodising. That process was probably a reason for more failures
when that was the mainstay than now.
This is an additional expense since rims in the circular form require
more space than extruded bars for the anodizing process. In any case,
the sidewalls are machined to have the "record groove" surface after
anodizing, another intermediate step that makes rims more than twice
as expensive as they need be.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: The Book, The Wheel, No Taco
Newsgroups: rec.bicycles.tech
Message-ID: <nXQ0b.13370$dk4.484941@typhoon.sonic.net>
Date: Wed, 20 Aug 2003 20:34:27 GMT
Martyn Aldis writes:
> Perhaps the move to anodized rims is not just a way of charging
> more. It could go with the move to alloys that are stronger (with
> the appropriate heat treatment) but are also less corrosion
> resistant. I think this lack of corrosion resistance could be the
> cause of the cracking problems not the surface finish but I have no
> solid evidence. I do not have information on what goes into the
> modern alloys for a start, let alone what heat treatment they get.
That doesn't make sense because rim failures began as a general plague
with the advent of anodizing and there is no doubt that the rim makers
were totally in the dark about the effects as they showed by their
promotional literature. They emphasized "Hard anodizing" giving the
relative hardness of the coating to aluminum and claiming that it made
stronger stiffer rims. Instead we got spoke pull-outs and
circumferential cracking.
After hefty debate here on wreck.bike the tone gradually changed and
anodizing got thinner. They couldn't just stop doing that because
then it would be an admission of guilt. So now we have occasional
failures and smartly colored rims. Ksyrium being the latest
escalation of expense without function. It has ALL the rave features:
Welded, anodized, sidewall machining, back side relief, and heavy.
> I've had a go to in this NG to see if anyone has anything to offer
> on stress corrosion cracking but it looks like nobody has.
>> and my skepticism of alodine usage by Mavic "back in the day"
>> http://groups.google.com/groups?q=willett+alodine&ie=UTF-8&oe=UTF-8&hl
> Yes alodine is a trade name for a particular conversion coating
> solution that has become generalised to mean dip or brush on
> conversion coatings in general. Although there are applications
> where conversion coatings are used as a final finish, rather than
> pre-paint, such as electrical shielding, as you say it does not
> appear to be an obvious choice for rims. Perhaps there is a rugged
> type that Mavic used.
> However, isn't this alodine thing a bit of a red herring?
Yes of course it is. We've been there before.
> The rims being sold now are anodized and they are said to crack more
> than the good old sort. Is the finish the cause?
Yes and it isn't a change in alloy that causes it. As I explained in
a simple but directly related analogy close to the flesh, bending a
scab on the knee will crack it and cause bleeding while softening it in
water and washing it off will allow even the new pink skin to withstand
the bending stress. A ceramic hard-coat (anodizing) works the same way.
> I've tried Google but I just get the same recycled stuff from this NG
> and other bicycle talk. What's needed are some solid references from
> materials science.
http://tinyurl.com/kn4d
List papers on the subject but does not display them.
http://www.poeton.co.uk/w1/a300.htm
Read under "Mechanical Strength/Fatigue Strength" and find:
"Hard anodising also reduces the fatigue strength of the base material by
approximately 47%."
I find that information on the web dodges around the issue and doesn't
even explain what causes the reduction in fatigue endurance if at all.
http://www.ase4anodising.co.uk/Hard.htm
http://www.acorn-nisil.com.au/anodising.html
http://www.hard-anodising.co.uk/tap_ha.asp
http://www.reactivesuspension.com/services.html
http://www.magnesiumcoating.com/w1/default.asp?page=design.htm
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: The Book, The Wheel, No Taco
Newsgroups: rec.bicycles.tech
Message-ID: <ymq3b.16146$dk4.534416@typhoon.sonic.net>
Date: Thu, 28 Aug 2003 16:47:26 GMT
Martyn Aldis writes:
> I think the question of why some rims crack after fairly modest and
> normal use is an interesting and legitimate one for a technical
> group. Jobst has given some useful links in this thread about
> anodization and reduced fatigue life (reduced by up to 47 percent if
> you anodize but do not use a suitable sealing process). He does not
> appear to give much credit to the technical people at Mavic or other
> rim makers. They can read anodization process specifications too
> and are well qualified to apply what they mean to the product as
> they will know what alloys and treatments they are using. He also
> has an idea about how the cracks in anodization could spread into
> the metal. There have been intelligent questions raised about
> limitations to this idea. There is a useful layman's introduction
> to crack propagation in the classic book:
> The New Science of Strong Materials or Why You Don't Fall Through the
> Floor by James Edward Gordon.
> http://www.amazon.com/exec/obidos/tg/detail/-/0691023808/qid=1062060018/s
> r=1-1/ref=sr_1_1/102-2458197-9842507?v=glance&s=books
What seems overlooked in the assessment of rim cracks is that my book
was written in the days when rims did not crack. Rims made by such
companies as Fiamme, Ambrosio, Mavic, Super Champion, Martano, Nisi,
Scheeren, and others. Wheels were built and tensioned as described in
the book, and lasted until they wore thin from braking or were
crashed. Cracked rims were practically unknown.
From what we have read in this thread, one might get the notion that
skills of extruding aluminum and choosing the alloy were lost at about
the time that Mavic introduce anodizing to rims. Those of us who
consciously witnessed that time, noticed that while great claims of
superior strength through hard anodizing were made rims began cracking
left and right, some cracking circumferentially through the side walls
into the hollow chamber leaving the tire on one half and the spokes in
the other. What's more is that at that time there was a shiny MA-2
and an anodized MA-40 of which only the MA-40 cracked.
Manufacturers weren't entirely blind to this but were not ready to
admit an error. Besides, they did not want to give up the
non-metallic (non-silver) aluminum rim. So now we have colored rims
that are anodized but not hard anodized, which reduces the tendency to
crack but does not get us back to polished rims, something that is
more durable and less expensive than anodizing.
> I tried in another thread to raise the question of very high
> strength alloys and stress corrosion cracking. I think that is
> interesting because it does not involve large numbers of stress
> cycles and may indicate that high static stress could be part of the
> problem. (That is why I suggested Brandt's law of spoke tension
> could be limited.) I had an idea some of these rims use 7000 series
> alloys that are more prone to corrosion problems than the 6000
> series but I now see Mavic say Maxtal is a 6000 alloy so that may be
> a dead end. As far as this group goes that thread disappeared into
> a discussion of motor industry politics at once while this thread
> turned into personal bickering. If anyone who follows this group
> actually knows anything about the technical details of these
> failures they do not seem to want to show their hand. They may be
> right that some views have become so entrenched that no progress
> will be made.
Why should one use an alloy that does not perform as well as a lesser
one in the face of proven reliability of the so called lesser alloy?
I suppose we could investigate stress corrosion and all sorts of other
diversions, but it remains that rims did not crack before all this
"material enhancement" came on the scene.
So what was the secret of all the shiny rims that did not crack in the
days of yore? Are we to believe that today's riders are all heavier
and stronger than those of, say Eddy Merckx's day and that they are
more demanding of their wheels? I don't believe a word of it.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: 14/15/14 vs. straight-gauge 15
Newsgroups: rec.bicycles.tech
Message-ID: <t1L3b.16441$dk4.541042@typhoon.sonic.net>
Date: Fri, 29 Aug 2003 16:18:33 GMT
Till Rosenband writes:
>>>> It's the most robust equipment that is available without a
>>>> significant price penalty. Why _not_ 36 holes, eh?
>>> Why not 24 holes? Why not 48 holes? etc.
>> I'm glad you asked. There is a best ratio between rim cross
>> section, spoke diameter and number of spokes. As the spoke count
>> is reduced, spoke tension must be increased to prevent slackening
>> in use. This demands a greater rim strength in bending to bridge
>> between spokes and it requires a stronger rim bed to prevent spoke
>> pull-outs. At the other end, hubs must be made stronger to retain
>> higher spoke tension.
>> Since spoke tension is limited by the circumferential compressive
>> strength of the rim, more spokes don't hurt although they cannot be
>> as tight as fewer spokes, but they can support a greater load
>> because it is distributed among more spokes. That is why 48 spokes
>> have served tandems well for those willing to ignore the fad of
>> fewer spokes. It boils down to how many spokes per length of rim
>> and for 700c rims it comes down to 36.
>> All this was developed from over 100 years of trial and error, back
>> in the days when the bicycle was an important transportation
>> vehicle and racers were not rich professional athletes who could
>> afford replacing wheels that failed readily. Of course this
>> doesn't affect riders who ride mainly new wheels and several sets
>> of them.
> You write that for regular bikes 36 holes are optimal, and "48
> spokes have served tandems well". I'm curious how the optimum spoke
> count scales with load. I think it's reasonable to assume that the
> tandem's wheels will carry twice the load of the 36 spoke wheels.
> Yet they only have 1/3 more spokes. I would expect a 48 spoke wheel
> to serve two riders about as "well" as a 24 spoke wheel serves one.
It is a matter of how many spoke fall in the load affected zone ad
that is not linear with load. I'm not saying that 48 spoke tandem
wheels are optimal, only that there is benefit in that number of
spokes using otherwise conventional dim profiles. I'm sure a better
cross section could be achieved for tandems.
> Imagine a 24 spoke wheel that is sitting on the floor and is
> carrying 100 lbs. It is bent out of round a bit to accommodate the
> load. If we now double the spoke count while simultaneously
> doubling the load, nothing should move. That's assuming the rim
> really acts like a wet noodle, the way you describe it in your book
> "The Bicycle Wheel". Even if rim rigidity played a role, the tandem
> rim might be twice as strong as the regular one, so I would expect
> the tandem wheel carrying 200 lbs to look very similar to the 24
> spoke wheel carrying 100 lbs. Hence the cyclical stresses will be
> similar in 48 spoke tandem wheels and 24 spoke regular wheels, and
> their durability should be the same, too.
> I've never ridden a tandem. Are 48 spoke wheels considered durable?
> Does anyone feel the need for more spokes?
I started the 48 spoke concept with Spence Wolf of Cupertino Bike Shop
when tandems in the 1950's suffered spoke and rim failures at a great
rate. In those days one cold request rims with different drillings.
In any case, the wheels made a big difference and have been used by
average sized tandem riders who travel.
Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA
From: jobst.brandt@stanfordalumni.org
Subject: Re: Mavic MA-40 - Piece of Crap?
Newsgroups: rec.bicycles.tech
Message-ID: <243Gb.4727$XF6.102893@typhoon.sonic.net>
Date: Tue, 23 Dec 2003 22:11:10 GMT
Jim Beam writes:
> Getting back to the ma40, all modern rims are made from extruded
> aluminum. Extruded aluminum, depending on subsequent heat
> treatments, will usually have a strongly anisotropic microstructure.
> [Just like striped toothpaste coming out of a tube.] Modern alloys
> are extruded much closer to their ductility limits than some of the
> older ones. It's part of what makes them strong. If one sees
> cracking following the extruded microstructure of a component, one
> /has/ to assume this microstructure plays a significant role in
> failure. I believe the ma40 was a somewhat unsuccessful attempt to
> push Mavic's then-used alloy to its limits but it's failure paved
> the way for the "open" rim series with a much superior alloy. The
> "open" series and their successors have not been as failure prone,
> regardless of anodizing.
I have a store of MA-2 rims and they are not anodized. They are
polished aluminum with a clear lacquer finish that just barely presents
an insulating I. surface rim displays electrical continuity with a
flashlight battery on its bead edge.
> I'm not sure if it's still up, but there was a very illustrative photo
> that showed the effect of microstructure on rim failure:
> in ASCII: The more common failure:
_______________ crack
> ______ ______
> / \ / \
> / \ / \
> ___| | ____| |____ crack
> | | | |
> \ / \ /
> \______/---- \______/
_______________ crack
> Lousy drawing, but this is supposed to show the photo with the two
> cracks initiating at the eyelet. This is important because if you
> look at an anodized rim with a magnifier, [silver 517 being a
> classic example], you will see cracks in the anodizing *radiating*
> around the eyelet where it has been punched through the rim.
> Straight out of the factory. Again, the anodizing cracks exactly
> radiate around the spoke hole.
You'll find that these cracks are aligned with extrusion marks and the
cracks of interest are those across bridging stresses from edge to
edge of the rim, there being significantly less bending stress between
spokes. That riveting eyelets and sockets causes crazing is not
unusual, however, the cracks of interest are those that lie across
principal bending planes. These are the ones that propagate into the
metal. Non anodized rims having no crust do not develop cracks as
readily although cracking is possible with cyclic overload. Steady
stress great enough to cause cracks would cause immediate failure
similarly to spoke failure.
> If anodizing were to be the sole cause of cracking, one would
> therefore expect to see the cracking exactly axial with the lines of
> the cracked anodizing, as we see for the crack on the left. And
> there would be no variation is this failure mode.
Not so. Those cracks are not in line with the principal stress,
however, there have been star burst failures on rims with sufficiently
thick anodizing.
> But on the right, this photo also showed cracking *tangential* to
> the spoke eyelet - i.e. /not/ following the radial cracks in the
> anodizing but following inherent flaws in the metal's extruded
> microstructure.
These all ran along the direction of extrusion, finally breaking
across the rim the slender bridge they made of the mid section of the
rim. This is one of the inherent disadvantages of extrusions.
> One *cannot* therefore solely attribute cracking simply to
> anodizing, whether it be hard, silver, black or purple. There don't
> seem to be any real micrographs on the net showing what extruded
> material looks like, but this is a good representation:
http://www.stud.ntnu.no/~fjeldly/forming.html
> Just like a piece of wood is easy to split along its grain, so can
> be a faulty extrusion.
Or for that matter a good extrusion.
> The ma40 was junk. Just throw it away. No, most modern rims do not
> have this problem.
Oh BS! A modern rim with anodizing presents the same failure. The
difference is that manufacturers are cutting back on anodizing
thickness.
Jobst Brandt
jobst.brandt@stanfordalumni.org
From: jobst.brandt@stanfordalumni.org
Subject: Re: Mavic MA-40 - Piece of Crap?
Newsgroups: rec.bicycles.tech
Message-ID: <U19Gb.4771$XF6.103661@typhoon.sonic.net>
Date: Wed, 24 Dec 2003 04:58:28 GMT
Jim Beam writes:
>>> Getting back to the ma40, all modern rims are made from extruded
>>> aluminum. Extruded aluminum, depending on subsequent heat
>>> treatments, will usually have a strongly anisotropic
>>> microstructure. [Just like striped toothpaste coming out of a
>>> tube.] Modern alloys are extruded much closer to their ductility
>>> limits than some of the older ones. It's part of what makes them
>>> strong. If one sees cracking following the extruded
>>> microstructure of a component, one /has/ to assume this
>>> microstructure plays a significant role in failure. I believe the
>>> ma40 was a somewhat unsuccessful attempt to push Mavic's then-used
>>> alloy to its limits but it's failure paved the way for the "open"
>>> rim series with a much superior alloy. The "open" series and
>>> their successors have not been as failure prone, regardless of
>>> anodizing.
>> I have a store of MA-2 rims and they are not anodized. They are
>> polished aluminum with a clear lacquer finish that just barely
>> presents an insulating -
> /is/ it laquer? Are you able to remove with the correct solvent?
It is lacquer and the edges of the bead have areas where the lacquer
has worn off from handling. These are unused rims with a mirror like
finish. Even if it were anodizing, if thin enough to conduct and
leave a mirror like shiny finish, it would be so thin as to have no
effect on crazing.
> As I said, Mavic sold these polished & anodized, but all the silver
> ones I've ever seen, and ;) I /have/ looked since we first discussed
> this, have definitely been anodized.
How did you determine that. At best, I believe they are clear alodine
finish as I pointed out to the last flood of Mavic apologists and
black anodized rim defenders. Clear alodine finish has a conductive
surface. That is why I specify it on many parts I design where
electrical conductivity and dimensional integrity are required.
>> - surface and the rim displays electrical continuity with a
>> flashlight battery on its bead edge.
> What does that prove? Laquer and anodizing are both insulators. If
> you were trying to say that your rims are polished, as is an old
> Fiamme rim I have, then it will conduct on any surface and you
> should readily see that.
What it proves is that it is not anodizing, something that doesn't rub
off and is not readily worn off by handling. To pursue your claim
that it is not lacquer would require rubbing them down with lacquer
thinner or paint remover, something I am not ready to do for your
curiosity. I intend to ride on these rims for a long time to come.
>>> I'm not sure if it's still up, but there was a very illustrative photo
>>> that showed the effect of microstructure on rim failure:
>>> in ASCII: The more common failure:
>> _______________ crack
>>
>>> ______ ______
>>> / \ / \
>>> / \ / \
>>> ___| | ____| |____ crack
>>> | | | |
>>> \ / \ /
>>> \______/---- \______/
>>
>> _______________ crack
>>> Lousy drawing, but this is supposed to show the photo with the two
>>> cracks initiating at the eyelet. This is important because if you
>>> look at an anodized rim with a magnifier, [silver 517 being a
>>> classic example], you will see cracks in the anodizing *radiating*
>>> around the eyelet where it has been punched through the rim.
>>> Straight out of the factory. Again, the anodizing cracks exactly
>>> radiate around the spoke hole.
>> You'll find that these cracks are aligned with extrusion marks and
>> the cracks of interest are those across bridging stresses from edge
>> to edge of the rim, there being significantly less bending stress
>> between spokes.
> I think we're on the same page, but which paragraph? Yes, the
> cracks that support the "anodizing only" hypothesis /do/ share the
> same axis as extrusion, but there's no definitive causal
> relationship between the two.
There is a direct relationship between cracking and stress
concentrations. These cracks are initiated by the hard surface crust
on the rim. I don't understand where you are trying to direct this.
The only difference between the MA-2 and MA-40 is anodizing. What
does all this diversionary metallurgical jargon have to do with this?
> I guarantee that a "bad" extrusion, unanodized, will fail in axactly
> the same way as your diagram, whereas a "good" extrusion, anodized,
> will not, or at least, not during a normal component lifetime. the
> "pull-through" cracks at the top & bottom of your diagram are not
> caused by cracking of the anodizing radiating from the spoke hole.
Now you are implying that the failed rims were bad extrusions. Are
you proposing that MA-2 rims were inspected for extrusion quality and
if found to be lacking, were relegated to the hard anodizing tank to
be renamed MA-40?
>> That riveting eyelets and sockets causes crazing is not unusual,
>> however, the cracks of interest are those that lie across principal
>> bending planes. These are the ones that propagate into the metal.
> You would expect, but not exclusively, which where my original diagram
> and the photo that it's based on came from.
Your diagram shows longitudinal cracks as does my additional picture.
These are not solely extrusion failures because they did not occur on
MA-2 rims.
>> Non anodized rims having no crust do not develop cracks as readily
>> although cracking is possible with cyclic overload. Steady stress
>> great enough to cause cracks would cause immediate failure
>> similarly to spoke failure.
>>> If anodizing were to be the sole cause of cracking, one would
>>> therefore expect to see the cracking exactly axial with the lines of
>>> the cracked anodizing, as we see for the crack on the left. And
>>> there would be no variation is this failure mode.
>> Not so. Those cracks are not in line with the principal stress,
> How not so? If the r/h crack in my diagram is not in line with the
> principal stress, then doesn't it argue a secondary cracking
> mechanism?
So? What explanation consistent with your radial crack theory do you
have for this occurrence? I didn't ignore stress direction. What you
choose to ignore is that for the previous 50 years, such cracks were a
rarity and were seen principally on tandems and other overloaded rear
wheels.
>> However, there have been star burst failures on rims with
>> sufficiently thick anodizing.
> See above. Yes, you /can/ see failures like that, and yes, that
> /would/ be anodizing induced.
>>> But on the right, this photo also showed cracking *tangential* to
>>> the spoke eyelet - i.e. /not/ following the radial cracks in the
>>> anodizing but following inherent flaws in the metal's extruded
>>> microstructure.
>> These all ran along the direction of extrusion, finally breaking
>> across the rim the slender bridge they made of the mid section of
>> the rim. This is one of the inherent disadvantages of extrusions.
> Extrusions are not inherantly flawed. Indeed, the opposite is often
> true. Flaws come with bad processing, bad q.c. and bad material
> selection.
Are you refuting your earlier claim of orientational structural
differences in extrusions. I don't understand your dodging and
weaving and ignoring the mass of failure evidence occurring subsequent
to the advent of anodized rims. A failure that was predicted and
subsequently occurred.
>>> One *cannot* therefore solely attribute cracking simply to
>>> anodizing, whether it be hard, silver, black or purple. There
>>> don't seem to be any real micrographs on the net showing what
>>> extruded material looks like, but this is a good representation:
http://www.stud.ntnu.no/~fjeldly/forming.html
>>> Just like a piece of wood is easy to split along its grain, so can
>>> be a faulty extrusion.
>> Or for that matter a good extrusion.
> Not if properly done.
You seem to be saying that all failures result from extrusion faults
when in reality extrusions are known to have orientation and strong
and weak axes, just as the wood you cite.
>>> The ma40 was junk. Just throw it away. No, most modern rims do
>>> not have this problem.
>> Oh BS! A modern rim with anodizing presents the same failure.
> Since when? what's a current anodized rim cracking failure rate?
> how does that compare to the same alloy unanodized? That's an
> entirely unsupported assumption.
It is hard to compare, there being no rims of the kind that failed so
readily. Today's rims are heavier, have a deeper cross section, and
have no broad flat inside circumference. Some of the rims are so
massive in the failure region that gratuitous machining is done there.
A process patented by Mavic. This machining coincidentally removes
the anodizing that would cause failures although at spoke
penetrations, wall thickness is so massive that no failures have
occurred there to my knowledge.
>> The difference is that manufacturers are cutting back on anodizing
>> thickness.
> Measurements please.
I see, you believe the lower failure rate is due to improving rim
extrusions, nothing else.
> Fyi, Mavic & Ambrosio are introducing shot peening and other
> "kinetic" compressive residual stress surface treatments. That
> should mitigate any last fear you have about premature fatigue in
> modern rims.
Oooh! I'm getting a headache from all these expensive "enhancements"
without which a plain polished 320 gm rim survived excellently years
ago.
Are you sure you aren't a government spin doctor who also interprets
political blunders as advances these days. I see your sig seems to
refer to government. Your apologist style makes me wonder in whose
employ you are writing this stuff.
Jobst Brandt
jobst.brandt@stanfordalumni.org
From: jobst.brandt@stanfordalumni.org
Subject: Re: Mavic MA-40 - Piece of Crap?
Newsgroups: rec.bicycles.tech
Message-ID: <u9uHb.5206$XF6.115274@typhoon.sonic.net>
Date: Sun, 28 Dec 2003 05:49:14 GMT
Carl Fogel writes:
> You might become fascinating by trying to put a number on how
> rapidly the MA-40 rims failed. Elsewhere in this thread, Jim Beam
> suggested that rims wear out from braking in only 25,000 miles, but
> that the accelerated fatigue of anodizing-induced cracking might
> become a problem in 40,000 miles.
Let's put it this way, many of the failed rims, specifically MA-40's
had not yet had their braking surface worn through to the metal when
they failed. I never rode on these, being aware of their drawbacks.
I had the opportunity to use someone else's MA-40 when he complained of
bad braking, which I verified before we switched front wheels back to
our own. That was my only experience.
> Or you might name the manufacturer and explain what part of which
> process you think that they don't understand (anodizing, machining,
> fatigue, or whatever) rather than leaving us to guess.
If you attend the InterBike trade show and talk to some of the
manufacturers, it becomes evident that some of these processes are
stabs in the dark for market share, with no sensible explanation for
doing so. Take mixed color treads on tires. If you ask why the
answers are contradictory since you need the best traction you can get
for braking straight ahead as well as while cornering, yet they one
manufacturer claims the green tread in the center is for braking and
the black on the sides for cornering while the next one will give the
same explanation for the reverse pattern.
None of them will tell how they came upon their crank attachment
scheme or for that matter it's advantages since they cant explain away
their previous design that was claimed to do the same things best.
For instance, the reason for the previous Shimano crank (spline)
attachment failures with people who stand, right foot forward, was not
understood although it seemed to be a random occurrence. You read its
cause here if you recall.
If you ask about anodizing, you get the same "harder, stronger, better
wear," etc talk you can get here, in spite of early rim failures that
were unknown prior to anodizing. This is akin to asking a bicyclist
who shaves his legs, why. The answers dodge that it is for the same
reason women or body builders shave... vanity, but practitioners don't
want to admit it, just as the anodizing folks don't. Its like the
black SUV and black windows. It's the IN thing.
Jobst Brandt
jobst.brandt@stanfordalumni.org
From: jobst.brandt@stanfordalumni.org
Subject: Re: mavic rims suck?
Newsgroups: rec.bicycles.tech
Message-ID: <W0tZb.2483$_3.40175@typhoon.sonic.net>
Date: Fri, 20 Feb 2004 19:15:02 GMT
Jay Beattie writes:
>> Here is one reference, if you look in the "ANODIZE" paragraph:
http://www.matronics.com/rv-list/hovan/tips/AlAnDef.html
>> Here is a good picture of a failure, never seen before rims
>> were anodized:
http://www.wiredfool.com/2003/06/25/impendingFailure
> Does the wearing off of the anodizing on the braking surface reduce
> the chance of anodizing-related failure on the worn area. In other
> words, if you rub it off, is it still a problem? I never really
> put-together sidewall failures and anodizing, assuming it was just a
> wear problem.
As you can see in that picture, the anodizing is still fresh and
whole, but even if it weren't, anodizing on the inside of the rim is
probably the greater culprit because it is there that the material is
under tensile stress that opened the crack. Besides, I believe crack
initiation from the hard crust has already begun shortly after putting
the rim in service... or even before that. When the MA-40 rim came
along, I inspected new rims under grazing incidence light and saw
crazing around spoke eyelets.
Jobst Brandt
jobst.brandt@stanfordalumni.org
From: jobst.brandt@stanfordalumni.org
Subject: Re: mavic rims don't *all* suck
Newsgroups: rec.bicycles.tech
Message-ID: <dPe1c.5397$_3.78799@typhoon.sonic.net>
Date: Wed, 03 Mar 2004 06:20:57 GMT
Tim McNamara writes:
> If you're referring to Bike Pro's Web site, then I'll reiterate that
> Bike Pro's stuff was not all that accurate, mainly being a
> repetition of hoary old myths and legends. The example already
> cited by someone else in the Bike Pro Web site that anodizing makes
> rims stiffer is a classic. However, there was also quite a bit of
> accurate stuff, and it was an attempt to provide much more
> information than most bikies had access to without paying the high
> prices of a Sutherland's or similar tome.
Actually anodizing make the rim measurably stiffer since the exterior
skin has a far higher modulus of elasticity than aluminum. The
problem is as soon as its tensile and compressive strength is exceeded
by any significant load, the stiffness is mostly gone leaving a crazed
hard skin that initiates the cracks under discussion here.
I can only repeat the example of a scab on you knee that stiffens the
skin but breaks as soon as the knee is significantly bent, blood being
the indicator. That is the most palpable example of material mismatch
similar to aluminum and anodizing that comes to mind readily.
Jobst Brandt
jobst.brandt@stanfordalumni.org
From: jobst.brandt@stanfordalumni.org
Subject: Re: Welding An Aluminum Rim
Newsgroups: rec.bicycles.tech
Message-ID: <5FH5e.13898$m31.136010@typhoon.sonic.net>
Date: Sat, 09 Apr 2005 03:06:41 GMT
Kenny Post writes:
> I have a Campy rim made of Aluminum. The rim was originally joined
> together by way of a metal sleeve which slots together both ends and
> is glued together making the hoop. About a year ago I hit a pot
> hole and the rim split apart at this metal sleeve. The metal sleeve
> is irreparable, but the rim is still good. I was wondering if it's
> feasible to have a welder weld the rim seam together and have the
> weld ground down smooth and flat to the braking surface. Can this
> be done and would this wheel be safe to ride on?
Don't mess with the welding. This is not something that can be done
other than by resistance welding in a fixtured machine and with a
slight oversize of the hoop that gets slightly shorter in the process.
As has been discussed here in the past, once the rim is tightly
spoked, it won't even need an alignment insert to operate under load,
the compression forces are great enough to keep the rim aligned.
Since this alignment is not there when you start spoking the wheel,
you either need an external guide, such as a C-clamp and pressure
plates both laterally and radially to hold the rim flush. Once
complete, a tight wheel puts insufficient shear stress on the cross
section to go out of alignment.
This was made clear in the days of tubular rims that were all aligned
with inserts of varying precision and often required a bit of lateral
shoving to avoid having a step in the brake surface. Many of these
rims were not held together. That is they could be manually pulled
apart before spoking.
If your rim s truly undamaged, build it up again as I described. On
the other hand, I can't imagine damaging the insert without bending
the rim.
Jobst.Brandt@stanfordalumni.org
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