From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: Clinchers vs. Tubulars
Date: 14 Dec 1996 18:09:54 GMT

Matt Haldeman writes:

> Why is colored tread inferior to carbon black? I am seeking info on
> this point...I haven't seen any specific reasons you may have posted
> earlier on this point so forgive my asking again if it's already
> been covered.

It has already been covered but it's been a while.  Carbon black for
obscure reasons, something that Mr Goodyear discovered by accident,
greatly improves wear resistance, and coincidentally, wet traction.
It does not make the rubber harder or softer as such, but improves
wear and traction.  The polymerization of butyl rubber changes its
wear rate and traction as well and that is what came along about ten
years ago when tires began lasting about twice the mileage.
Specialized Touring II tires wore out about twice as fast as current
tires that use newer compounds, however, carbon black was and is the
most important feature in traction.

Colored treads do not contain carbon black or they would be black,
because the amount of carbon is substantial (over 25%).  Because
appearances are more important than function in today's society, tire
manufacturers are producing colored tires for automobiles even though
they are poorer in wear and traction than black tires, but to make up
for that they cost more, as do bicycle tires with color.

Jobst Brandt      <jbrandt@hpl.hp.com> 

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Best cornering tire profile???
Date: 9 Nov 1998 21:27:20 GMT

Jere Cunningham writes:

> So lets get down to details, what sort of descending, on what
> surface, and what kind of tire are we discussing here?

> Road bike, road tires (Conti Gran Prix vs Michelin Synergics),
> asphalt, tightly curving downhills of 3-5 miles.

As I said, you cant feel any difference on good road tires until they
slip out on you.  That's why hard cornering is such a rarely practiced
skill.  Most riders have no idea where the limit is and finding it
hurts.  That is why the Avocet tire tester was designed, so that the
maximum lean angle could safely be determined.  The washout angle is
precipitous and repeatable.  Bicycling just performed a series of
tests on that and published a muddled report on what they found using
this machine.

I designed this machine to verify that slicks are the best cornering
tires and that on clean dry pavement, 45 degrees is a good limiting
angle.  Tires with profiled tread all perform worse than slicks, but
then you know that from drag racers, racing cars, and racing
motorcycles that all use slicks.

Colored tread is a fad and fashion statement.  This becomes apparent
when the makers put different rubber on the center of the tire than at
the sides, some use black in the center others use colored.  Their
explanations diverge enogh to makes these marketing ploys obvious to
the wary observer.  You need maximum traction upright when braking
hard into a turn and you need maximum traction when you are leaning
hard in that turn.  Now where do you think that leaves room for two
kinds of rubber, wear durability being greatly subordinate to good
traction?

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Continental Tires Dangerous?
Date: 23 Apr 1999 17:03:06 GMT

Bill Little writes:

> Just curious Jobst, what do you ride?  I've seen some implication
> that you ride Avocet.  Which model and what kind of mileage do you
> get?  I have been successful with continental grand prix (I got 5k
> on the pair last summer, no flats, the back is looking a little
> ragged) but I am open to advice.  The local bike show had Michelin
> Axial Pro for ~$25 US so I'm trying them this year.

I rode Clement Campionato del Mundo tubulars and some Paris Roubaix
until Specialized offered the Touring II so called 700-28c tire,
the first reasonably available and durable clincher.  I never turned
back from clinchers, having ridden many miles and repaired many tires
until then to the degree that I was solidly familiar with the problems
of tires.

When Avocet decided to enter the tire market I convinced them to make
a smooth tread tire, a slick, because that is essentially what we rode
in the days of tubulars, the tread of those tires being about 1/2mm
deep when new.  Fortunately there was no time to make any other tread
pattern before the introduction date, so I got my tire as well as a
whole line of slicks.  These tires competed with Specialized that had
the majority of the high performance market although Michelin also had
a slick that had a tread that aged and cracked rapidly at that time.
The Avocet, made by IRC, had a new compound that doubled tire life
while having as good or better traction than other tires.  Today
most tires have a similarly wearing tread.

Wear rates of tires can be compared by the roughness of the surface
after climbing the same hill.  The otherwise smooth surface wears into
characteristic waves, called Shalamach waves, whose period is
proportional to wear rate.  The difference between Avocet and Touring
II tires was more than 2:1.

My first experience in durability was on my annual Alpine tour where,
in the past, I had to rotate tires in the middle of the trip to go
2000 miles with Touring II tires.  The Avocet tires last about 3000
miles on this kind of riding for me.  The amount of climbing is
apparent in the trip reports in the URL below.  During the rest of the
year I put on half my mileage riding to work on the local hills so I
get far more per tire.  I use the Road 20 (steel bead, no Kevlar) tire
and am completely satisfied.

http://www-math.science.unitn.it/Bike/Countries/Europe/#Jobst

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: Best clincher tyres for road racing
Date: 20 Jan 2000 18:11:46 GMT

Rob Kaufman writes:

>> What concerns me more are the colored tires that have poor traction
>> on wet surfaces and poor wear, but fashion seems to be more
>> important than safety.

> The only independent tests of wet traction I know of, were done by a
> German cycling magazine.  I do not have the material available at
> the moment, but my recollection of the results is that only colored
> tires with silicium had wet traction worth a damn, but it was still
> about 10% less than a carbon black model from the same manufacturer,
> and presumably of similar construction.

(German) Silicium : (English) silicon

> However, the best silicium colored tires (continental, Vredestein
> and Michelin) were better some brands' carbon black tires.  I
> believe the claims of lower rolling resistance were also confirmed,
> but it was not as great a difference as the manufacturers claim.

> Correct me if I'm wrong, or share some more data with us.

In the days of yore, Clement made tubulars for extra low rolling
resistance that were not black.  For smooth tracks pure latex was used
while a special red tread was offered for criteriums.  Most of us
tried these and eventually rode in the rain to discover their lack of
wet traction.

The colored tire effort was begun several years ago to market mini
cars like the Smart, that was to have color matched tires.  The
European auto trade publications reported that although the tires were
nearly as good as black ones, they were not ready for the market, to
put it cautiously.  Nothing has been said in a few years on this project.

My reading is that they chose to shelve it for now and let the bicycle
industry use it where fashion is more important than function.

> (I stocked up on Michelin Supercomp HD tires when they were discontinued and
> went on sale, but I am running low.  What now, Avocets?)

And why not.  As long as I have anything to say about it Avocet will
continue to offer their high performance smooth black tread.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: New Light Clinchers
Date: 21 Mar 2000 00:53:00 GMT

Jim Feeley writes:

>> Colored rubber doesn't hold worth a damn on wet roads and doesn't
>> wear as long as black rubber..

> Is that universally true? If so, why?  I could guess but perhaps
> someone knows for sure why that may be.

http://www.columbianchemicals.com/about/rubblack.htm
http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/carbonbl/basic_cb.html
http://www.stw.nl/projecten/T/tst4489.html

This last reference indicates that silica instead of carbon has not
achieved the performance of carbon.  Low RR can be achieved without
silica or carbon and has been used for TT tires has been used about as
long as track racing has existed.

I'm sure some web searchers can find more.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Rotating tires
Date: 13 Jul 2000 16:04:44 GMT

Bob Mitke writes:

>> Besides, most of the folks who wouldn't ride slicks when they first
>> came out a few years back, are now riding not only slicks, but
>> colored slicks, the slipperiest tires made.

> What is the magnitude of the difference in the frictional
> coefficients between colored and black bicycle tires (holding
> everything else constant)?

It's enough to make riders fall on wet curves you wouldn't suspect as
limiting.  The colored tires were developed for small cars in Europe
but never achieved road performance, both wear rate and traction, that
was necessary for introduction.  The whole project got pushed off to
bicycle tires where customers are perpetually snowed by the hype.

> Furthermore, will the vast majority of the people purchasing tires
> be able to perceive the difference in performance of a colored tire
> as opposed to a black tire?  I have ridden a lot of tires, colored
> and otherwise.  There are a lot more important things to worry about
> than color...

So why buy colored tires?  They cost more, wear out faster, and slide
on wet pavement.  I don't buy it.  Color IS the most important feature
for most (aka vast majority aka overwhelming majority) riders.
Falling on an average wet curve doesn't seem to convince people.  They
attribute it to their own lack of skill.

> If we limit the topic to cornering, I would think that the magnitude
> in cornering speed gains would be significantly greater if you were
> to work on the proper cornering technique as opposed to switching
> the color of your tires...

I think you confuse getting through a turn fast with safely leaning
the bicycle.  People have two problems in cornering, picking the best
line, and how far one can lean (of which estimating the speed/lean
ratio is a part).  However, if the tire has poorer wet traction than
what one previously had, then wet riding becomes a hazard.

> I think I remember the old Avocet Fasgrip adds had some stuff about
> cornering speeds and friction coefficients (I remember the ad with
> the guy leaning over in a turn and a blow up of the contact patch or
> lean angle or something).  Perhaps you could refresh my memory about
> the technological claims in their ad campaign and comment on their
> relative significance to the average bike rider...

They have measurably lower rolling resistance, longer tread wear, and
better cornering traction.  These attributes were measured, published
and shown graphically.  The picture to which you refer is the third in
the web site below:

http://www-math.science.unitn.it/Bike/Countries/Europe/Tour_Reports/Tour_of_the_Al

>> Hey, but what's more important, the look or the way it works.

> In my opinion, the first slick tires attracted attention to
> themselves because they were differentiated from the competition by
> their aesthetics.  Only after a customer is interested in these
> unique looking products can they be educated about any possible
> benefits (minute or otherwise)...

I think there is more to it.  The merits of the slick tire were argued
here endlessly by riders who were sure that the micro-tread patterns,
ones that mimic automobile tread patterns, gave perceptible advantage
on wet pavement because it prevented hydroplaning.  There is no
hydroplaning for bicycle tires of this size.  In contrast, it took no
effort to get people to buy colored tires.  Colored smooth tires.

Just to underscore that, we read here of people who want to color their
natural colored skin-walled tires with shoe polish so they can make
their tires look as 'functional' as the others.

> A commercially successful design accomplishes both of the following
> tasks (among other things):

> 1) aesthetics

> 2) functionality

The function being appearance?

> Colored tires work for the vast majority of people under the vast
> majority of conditions.  Color just happens to satisfy point #1
> above.  The underlying technology is still functional.

How does that make up for the poor wear rate and wet traction?

> If functionality was the only design goal for the products we buy,
> our lives as consumers would be pretty boring...

I see.  You find bicycling boring.  So why do you ride?  It couldn't
be to display gaudy and esoteric equipment?

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Colored Tires?
Date: 19 Jul 2000 20:56:13 GMT

Shawn A? writes:

> Occasionally I catch references to "colored tires being inferior" on
> various threads on this board.  The snippets claim things such as
> lower c of friction, poor cornering, poor handling in the wet, etc.
> I understand that the colored tires use something other than the
> traditional carbon black on top of the casing (silica?) but alas, I
> missed the original discussion.

In an effort to sell micro-cars in Europe with color matching tires,
non black tires were developed but without success.  Carbon black in
tire rubber gives it both wear resistance and wet traction, features
that were not achievable with other non black tire compounds.  That
carbon black is an essential element in tire tread is well known.  How
to make an equivalent tire without it is not yet known.

> Can someone please explain what is going on here?  Any references to
> actual tests or measurements would also be appreciated.

We have been waiting for such tests, but all I have are reports in the
European auto press that the tires failed to meet requirements in both
wear and wet traction.  Shortly after these reports, colored bicycle
tires came to the market.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Colored Tires?
Date: 20 Jul 2000 21:28:10 GMT

Shawn A? writes:

>> Carbon black in tire rubber gives it both wear resistance and wet
>> traction, features that were not achievable with other non black
>> tire compounds. That carbon black is an essential element in tire
>> tread is well known. How to make an equivalent tire without it is
>> not yet known.

> Thanks for the straight answer, but I am still missing something.
> Your statements seem to imply that tires without Carbon Black are
> inferior--you site wear resistance and wet traction.  You also post
> that no measurements are available for the new compounds...
> therefore, I assume you are referring to historic attempts at making
> colored tires that failed miserably, and not the modern breed.  So I
> ask, what were they doing and how (in a quantifiable manner) did
> they fail?

The last "old" style tires were the Specialized "Umma gumma" tires for
the 7-11 team that were never used after too many crashes in training
in the rain.  The tires in question today use silica filaments like
chopped up fiberglass (I have only read about them) that are supposed
to make up for carbon black while not adding color that can be
achieved by pigments as desired.  That carbon black has the effect on
rubber that it does was not understood when it first occurred by
accident in the making of tires.  The chemical and physical effects of
the combination has some unexpected synergy.  I don't know anything
about that other than that it works better than any substitute yet
found.

> Also of interest is why Carbon Black is so good at wear resistance
> and wet traction.  I understand a little about CF in the dry but
> what happens in the wet--thin films and such?  What property does CB
> have that is hard to replicate with colored compounds?

It's not the colored compounds that affect wear and traction, but
rather the silica that is part of the rubber mix in lieu of carbon
black.  Friction occurs on a microscopic level that is not readily
apparent.  We see this by the many worthless tread patterns and sipes
that come and go with tires.  Pavement traction involves the surface
microstructure of the sand and gravel from which it is made, not the
sand and gravel itself.  That is why wet slick (steel gratings or
paint stripes) surfaces remain slick regardless of tire tread patterns.
A homogeneous material is easily polished and the harder the smoother.
On the other hand, rubber with no additives is not only smooth but it
presses against another smooth surface with no hard asperities that
might penetrate a water film.

What may be less apparent is that in thin films liquids do not behave
as one might expect and cannot be easily displaced.  That is why oil
in ball bearings can provide fluid separation between balls and races.
Similarly, a squeegee glides effortlessly across a wet pane of glass
on a boundary layer of water even though it has a sharp edge.  Carbon
black apparently enables rubber to not tear or abrade on the
asperities in pavement aggregate.  What the effects are is unclear to
me but that it works and is dependent on carbon black is clear to me.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Colored tires
Date: 27 Jun 2001 21:50:03 GMT

Pete Biggs writes:

>> Colored tire rubber was developed for the auto industry to go with the
>> micro cars such as the Smart by DB and others so they could color
>> coordinate the cute little vehicles.  When the process could not
>> produce a tire that had god wet traction and reasonable tire life, the
>> project died.  You haven't seen colored tires, other than white walls,
>> on cars or motorcycles for that reason.  You definitely won't see them
>> on racing cars in the near future.

> 'Lot of questions:--     (As this is a technical forum, hard facts and
> detail would be valuable for such an important issue).

I have no tests.  The history comes from the European auto magazine
Auto Motor & Sport where the progress of these tires was qualitatively
reported over several years and then laid to rest when the tires never
produced either acceptable wet traction or war life.  That was about a
year or so before the rubber began appearing on bicycle tires.

Items such as the following make big promises but didn't deliver.  I
find interesting that the emphasis is on rolling resistance rather
than the heart of the matter, which to me is traction and wear.

http://www.rubbernews.com/subscriber/technotes/073195.html

> Is the concern 50/50 between life and traction for motor racing, or
> is life more of an issue?  After all, bicycle tyres don't get such a
> scrubbing or such mileage.  Note. Vittoria coloured bicycle tyres
> have black central tread for increased life.

Many of these tires do not use carbon black for the black rubber and
besides, there are two conditions that require optimal traction,
braking and cornering and the combination of both.  Therefore, colored
tread anywhere within the contact patch is a detriment to performance.
Besides, as I mentioned often, the same people that were afraid of
carbon black slick tires are now riding slick colored tires with no
qualms.

> Are all coloured compounds as bad as each other?  Have any traction
> tests been done on the current crop of coloured tyres?  Have they
> improved in recent years?  It would be useful to know how many
> degrees fewer a bike could be leaned over with coloured tyres.

The problem is lack of carbon black, not the color.  Color is only
possible with silica, which is clear/white.  Carbon black overwhelms
any color added.

> If the coloured stuff is softer, doesn't that mean it's more grippy?

It may be when dry but it is not when wet.  Clement made TT tires, not
to be used in the rain, that had red tread with no carbon and no
silica for lowest RR.  The lowest RR track tires used 1mm thick latex
treads on bare wall silk casings.  Glues on with track glue, these
tires probably fell off the bottom of RR charts, having condom thin
tubes.  You can't have the best of all worlds all the time.  These
tires were no good anywhere but on board tracks, even concrete wore
them out in one meet.

Jobst Brandt    <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Colored tires
Date: 28 Jun 2001 00:11:18 GMT

Terry Morse writes:

>> Items such as the following make big promises but didn't deliver.  I
>> find interesting that the emphasis is on rolling resistance rather
>> than the heart of the matter, which to me is traction and wear.

>> http://www.rubbernews.com/subscriber/technotes/073195.html

> Carbon black is also a UV inhibitor. I wonder how colored tires will
> stand up to UV radiation without carbon.

On bicycles, no different because they wear out so fast.  On the other
hand, we know what white-walls do.  They oxidize and crumble so you
can scrub off the old rubber with a brush when you wash the car.

Jobst Brandt    <jbrandt@hpl.hp.com>