From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: Delta Patch Kit Efficacy
Date: 5 Jun 1997 20:36:53 GMT

Brian Ray writes:

> Anybody had similar problems with these patches? I've got butyl
> tubes, I think this is a for-butyl patch kit (perhaps I'm a complete
> idiot here--I know Delta makes latex tubes). I think I'm following
> the instructions exactly: rough up the tube, apply the cement, let
> dry for a few minutes, then smoosh the patch onto the tube and press
> it for a few more minutes.

Among the things you mention, "roughing up the tube" is not the
purpose of the abrasive in the patch kit.  The intent is to remove the
mold release agents that remain on the surface of the tube from
manufacture.  The mold release will release the patch if not removed.
That is why the tube must be scrubbed until it has a matte finish.
That is to say, its glossy skin must be removed.

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.misc
Subject: Re: Dumb question
Date: 4 Jun 1999 19:55:13 GMT

Noah Wildman writes:

> I have yet to satisfactorily glue patch a blown tube. I seem to not
> be able to find an answer to a seemingly simple question. How long
> does one let a patch set until its ready to be inserted and
> reinflated?

You didn't say whether you are using self adhesive patches or ones
that require application of liquid glue to the inner tube.  Self
adhesive patches perpetually have the problem of newly applied glue
patches because they do not make a chemical bond with the tube and can
always be peeled off unlike well set glue patches that cannot be
removed mechanically... that is without solvents that dissolve the
patch.

On that subject you might wamt to read an FAQ item:
----------------------------------------------------------------------
Subject: 8.59  Patching Tubes
From: Jobst Brandt <jbrandt@hpl.hp.com>

The question often arises whether tubes can be practically and safely
patched.  I suppose the question comes up because some people have had
leaky patches or they consider it an arcane exercise.  Either way, it
need not be difficult if simple rules are followed.

Mold release

Tubes are made in metal molds to which they would stick if mold
release were not sprayed into the mold.  The release agent is designed
to prevent adhesion and it will do the same for patches because it
remains on and in the surface of the tube.  To make a patch stick,
this material must be removed.  That means, the sand paper in the
patch kit is not to roughen the surface but to remove it.  Not
removing the 'skin' of the tube is a major reason for leaky patches.

Once the mold release has been removed, rubber solution can be applied
with the finger by wiping a thin film over the entire area that the
patch is to cover.  After the glue has dried so that no liquid or
jelly remains, leaving the area with a tacky sheen, the patch should
be pressed into place.  Patches can be made from tube material but
this must be done carefully following the same procedure as preparing
the tube.  The trouble is that butyl tube material, unlike patches, is
impervious to rubber cement solvents and will never cure if the glue
is not completely dry.  This presents a substantial problem.

Patches

Patches commonly have a metal foil cover on their sticky side and a
cellophane or impervious paper cover on the other.  The foil should be
pulled off to expose the adhesion surface and the patch pressed into
place.  The backing paper or cellophane often has perforations that
will break if the tube and patch are stretched.  This makes peeling
the cover from inside to outside of the patch possible and prevents
peeling a newly installed patch from its position.

REMA patches, the most commonly available in north American bicycle
shops, have a peculiarity that not all have.  Their black center
section exudes a brown gas that discolors light colored tire casings
in daylight.  This causes the brown blotches often seen on sidewalls
of light colored tires.

Leaky Patches

Assuming the patch was properly installed, it will still possibly leak
after a few miles, if used immediately after patching.  Because the
tube is generally smaller than the space inside the tire, to prevent
wrinkles on installation, it will stretch when inflated as does the
patch.  Although it stretches less than the rest of the tube by the
greater thickness, it resists stretch more than the tube alone.  Under
the patch, the stretched tube tends to shrink away from the patch, and
because there is no holding force from inflation pressure at the hole,
the tube can peel away from the patch that is held by air pressure.

If the puncture is a 'snake bite', the chances of a leak are even
greater.  Pinch flats from insufficient inflation or overload are
called snake bites because they usually causes a pair of holes that
roughly approximate the fang marks of a snake.  These holes are near
the rim where the contour of the tube is nearly a sharp fold.  This
location is especially susceptible to the tube separation at the hole
closest to the rim.

In a rolling tire, the patch and tube flex, shrink, and stretch making
it easier for the tube to separate from a partially cured patch.  To
test how fast patches cure, a patch can be pulled off easily shortly
after application, while it is practically impossible after a day or
so.  For best results, the freshly punctured tube should be patched
and put in reserve, while a reserve tube is installed.  This allows
a new patch more time to cure before it is put into service.

A tube can be folded into as small a package as when it was new and
practically airless, by sucking the air out while carefully using the
finger opposite the stem to prevent re-inflation.  This is not done by
inhaling but by puckering the cheeks.  Although the powders inside the
tube are not poisonous in the mouth, they are not good for the lungs,
but then that's obvious.

Minutia

The difficult part of loose patches is that separation always stops at
the edge of the patch because air pressure prevents further
separation.  The annoying intermittent slow leaks that occur, often
close when the tube is inflated outside a tire, so the offending patch
cannot be found.  Old tubes to be discarded often reveal partial
failures by cutting through the center of patches with shears.

Tires are less flexible at a patch and will wear slightly faster
there, but patches have no effect on dynamic balance since wheels are
so imbalanced that patches have no effect on the heaviest position of
the wheel.  Heat from braking can accelerate separation of a fresh
patch but this generally does not pose a sudden hazard because lifting
patches most often causes only a slow leak.

------------------------------

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Confetti (Was How man times?)
Date: 28 Aug 2000 16:12:13 GMT

A? Muzi writes:

> Tubes used to come with a dusting of talc and it's still a good
> idea.  For patching, an alcohol prep is way faster and more
> efficient than a scraper.

I take it, you carry a bottle of alcohol with you on bike rides; and
where do you keep it?  The purpose of sanding the tube is to remover
the skin that contains residual mold release from manufacture.
Alcohol does not dissolve the rubber, and therefore, does not get rid
of the mold release.  A piece of beltsander cloth is an ideal abrasive
in contrast to those scratch pads in the metal lids of auto part patch
kits that do nothing but put scratches in the tube that must be filled
with rubber solution.  Plastic ones only polish the tube.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: How man times?
Date: 26 Jul 2000 20:50:35 GMT

Dave Blake writes:

>> As was mentioned, run your thumb around the inside of the tire to
>> feel whether there are other sharp objects.

> I would recommend visual inspection first. If something is sharp and
> tough enough to pierce the fiber casing of the tire, it will quite
> likely go right through your skin as well.

In theory that sounds good but in practice these objects don't cut the
thumb that swipes.  I know of no one in my circle of friends who has
had such an injury nor have I had one over many years of the practice.
This fear is similar to theoretical inhalation of talcum from sucking
air out of an inner tube to flatten it for folding.  Air is not sucked
with the lungs but with the mouth, but then that's obvious if you have
done it.  Just the same, like "never brake in a curve", these dire
warnings propagate like chain letters with no visible means of support.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jobst.brandt@stanfordalumni.org
Subject: Re: How much glass don't we see?
Newsgroups: rec.bicycles.tech
Message-ID: <vkBBa.18126$JX2.1113766@typhoon.sonic.net>
Date: Fri, 30 May 2003 04:44:11 GMT

Jasper Janssen writes:

> Because *if* there's something on there that's loose enough to brush
> off, you've got 50% chance of banging it in instead of taking it
> out, and 50% chance of having it pierce your gloves and making you
> remember when you last got tetanus shots.  Especially glass shards go
> through gloves like a hot knife through oil.

Oh you lie!  What about bare hands?  That's the same bugaboo that
people fear when patching a tire.  They don't want to run their thumb
around the inside of the tire casing to find the cause of their
puncture for fear of bleeding to death.  Your scenario only adds to
that fear.  What do YOU get out of that?

I and riding companions have been wiping tubulars in the old days and
wiping the inside of clinchers for nigh on 50 years with no such
incident.  I have often volunteered to run my thumb around the inside
of fearful tire patchers on the road, unable to convince them of its
safety... mainly because people like you keep the bloody myth alive.

It is not impossible, but highly improbable, and until you get even a
small scratch in the thumb, you better do it to find the obstacle.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Glass and tire wiping
Newsgroups: rec.bicycles.tech
Message-ID: <BqMCa.18873$JX2.1162559@typhoon.sonic.net>
Date: Mon, 02 Jun 2003 18:10:41 GMT

Sam Huffman writes:

>> I too learned the "feel for the seat stay" trick.  Quit wiping a
>> few years ago, though, and haven't noticed any difference in flat
>> frequency.

Saved a lot of dirty hands as well, I'm sure.  I came to that
conclusion on the first few rides with wiping riders, from observing
how many wheel revolutions passed before the wipe began.  It didn't
make sense and the analysis makes it even more preposterous.

> Out of curiousity, what happens when something more significant than
> glass is also on the tire? I got a flat the other day after riding
> over a small patch of glass. The glass didn't cause the flat but a
> wood staple I hadn't seen did.  One of the sharp points was embedded
> in the tire and the other wasn't.

This is the old bugaboo that migrates to finding the offending cause
of a flat tire while patching.  As was discussed in a related thread,
these tales keep anxiety up and the image of gushing blood vivid.
Keep it up.  However, It doesn't readily happen and has never occurred
in my bicycling experience.  It is theoretically possible but don't
bet on it.  Finding the wire, glass, or thorn by wiping the thumb
around the inside of the tire is not hazardous and is essential to
keeping air in the tire.  Even Michelin wires, that are fairly common
on roads, need be found by braille when patching.

> It seems to me that wiping the tire could easily have resulted in
> slicing my hand open with the staple, glove or no.  Has anyone
> experienced this?

Only if you ignored the rotation piece of hardware that was going
click-click-click as you rode.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Glass and tire wiping
Newsgroups: rec.bicycles.tech
Message-ID: <ccPCa.18931$JX2.1163939@typhoon.sonic.net>
Date: Mon, 02 Jun 2003 21:20:08 GMT

Sam Huffman writes:

>> However, It doesn't readily happen and has never occurred in my
>> bicycling experience.  It is theoretically possible but don't bet
>> on it.  Finding the wire, glass, or thorn by wiping the thumb
>> around the inside of the tire is not hazardous and is essential to
>> keeping air in the tire.  Even Michelin wires, that are fairly
>> common on roads, need be found by braille when patching.

> There is a significant difference between encountering a very small
> sharp object (not even readily visible to the eye) while slowly
> rubbing one's finger around the inside of a tire and encountering a
> 0.5" staple leg at perhaps 150 rpm. Particularly when the hand
> cannot be removed quickly. Do you have any reason to believe this
> couldn't happen?

> It wouldn't surprise me that this has not happened to you, since you
> are not a tire-wiper. That is why the query was posed to those who
> are.

>>> It seems to me that wiping the tire could easily have resulted in
>>> slicing my hand open with the staple, glove or no.  Has anyone
>>> experienced this?

>> Only if you ignored the rotation piece of hardware that was going
>> click-click-click as you rode.

> Unfortunately there was no "click-click-click". After maybe 25 yards
> the only sound I heard was the *pfft* - *pfft* - *pfft of escaping
> air.

Nature is also at work here and a forward leaning protuberance on a
tire gets bent back and flat against the tire.  The likelihood of the
scenario so often pictured here as you have does not occur and not
because people don't manually wipe tires, but because protruding glass
is broken off and exposed wires bent back.  You need to look at the
occurrences and decide why they don't exist.  When I first began
bicycling tire wiping was THE rave.  None of these folks had the
slasher incident that is so often portrayed in this space.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tire cord problem...
Newsgroups: rec.bicycles.tech
Message-ID: <0TMCa.18877$JX2.1163037@typhoon.sonic.net>
Date: Mon, 02 Jun 2003 18:41:00 GMT

anonymous writes:

> Are there steel cords in Continental Ultra 2000 tires?  I thought I
> had picked up some glass but there was not a visible puncture from
> the rod side of the tire.  I felt around on the inside of the tire
> and ran across what appeared to be a steel belt or wire coming from
> the center of the casing that was causing the flats.  I broke out
> the trusty Leatherman and whittled away at the wire? thing that was
> causing the flats until it was gone.  But the curiosity of having a
> steel wire coming through is surprising.  I also wondered, if the
> cord was broken, am I more at risk for some catastrophic failure
> when I hit a corner at speed?  The tires don't have 750 miles on
> them...

Congratulations, you have just picked up a "Michelin wire", Michelin
being the inventor of the steel belted radial tire that today is made
by many tire makers.  You should have pulled the wire out.  It is not
a normal part of your tire although the wires are common on roads.  We
don't see them often because they lie flat on the road.  My experience
is that they enter only rear tires because they must first be tilted
up by the front tire... or a closely preceding rider, although I've
never seen that happen.

That gets us back to why rear tires statistically have more flats than
front tires.  It is not from the heavier load on the rear wheel as
myth and lore would have us believe, but rather that debris lying on
the road must be tilted up to enter a tire, something the front wheel
does well.  It is also the culprit in ripping off derailleurs with a
"derailleur stick" that lies flat on the road or trail and gets tossed
onto the chain directly ahead of the derailleur.  Bingo!

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tire cord problem...
Newsgroups: rec.bicycles.tech
Message-ID: <dOTCa.18985$JX2.1167090@typhoon.sonic.net>
Date: Tue, 03 Jun 2003 02:33:45 GMT

Dave M Wyman writes:

>> That gets us back to why rear tires statistically have more flats than
>> front tires.  It is not from the heavier load on the rear wheel as
>> myth and lore would have us believe, but rather that debris lying on
>> the road must be tilted up to enter a tire, something the front wheel
>> does well.

> That explains two annoying flats. Three weeks ago my rear tire was
> punctured by a three inch nail. The nail pushed through the tread, then
> in and out of the tube, and then out the tire's sidewall - I assume the
> tire is ruined, although the puncture diameters are rather small. It was
> an almost new tire, and an expensive one, to boot.

> A year and a half ago, my rear Specialed "Fatboy" slick rolled over a
> piece of glass shaped and sized like an arrowhead! The hole in the tire
> was significant - after I pulled out the piece of glass, I put in a new
> tube, put a patch on the inside of the tire, and then rode half a dozen
> miles home with my fingers figuratively crossed.

My pursuit of these questions started at an early age.  This one arose
when my father told me that rear car tires get more flats than front
tires because the driving torque sucked them in.  I was in the first
grade at that time and  my father was an economist, not an engineer.
However, it started me on questioning any such claim that wasn't
substantiated by some reasonable explanation, be that about cars,
airplanes or bicycles.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tube Patching Question
Newsgroups: rec.bicycles.tech
Message-ID: <dsUCb.2711$XF6.61089@typhoon.sonic.net>
Date: Sun, 14 Dec 2003 07:38:49 GMT

Bob who? writes:

> I was patching some tubes today and read the following in the
> instructions.

> "...the patch starts the vulcanization immediately but the complete
> vulcanization is achieved only after the tire runs on the road."

> What ramifications does the above statement hold?  How long can I
> wait before using my now patched tubes, etc?

First: It is not true that the common patches vulcanize.  If you want
to try it, just heat a patched tube by pressing the patch against a
fairly hot Teflon coated frying pan.  This is the best method of
pulling off an old REMA patch.  Vulcanized patches do not come off.

Unless the patch is fairly well cured, rolling on the road only helps
lift the patch... from the inside to outside starting at the hole.

http://draco.acs.uci.edu/rbfaq/FAQ/8b.1.html

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tube Patching Question
Newsgroups: rec.bicycles.tech
Message-ID: <9BbDb.2812$XF6.65376@typhoon.sonic.net>
Date: Mon, 15 Dec 2003 05:25:25 GMT

Pete Biggs writes:

>> First: It is not true that the common patches vulcanize.  If you
>> want to try it, just heat a patched tube by pressing the patch
>> against a fairly hot Teflon coated frying pan.  This is the best
>> method of pulling off an old REMA patch.  Vulcanized patches do not
>> come off.

> That's disappointing.  My Velox patches that appeared to be
> vulcanized have failed the frying pan test.  Still, they normally
> stick and stay stuck very well.

> Why is cement sometimes called "vulcanizing rubber solution"?

Snake oil!  It sounds good and I bet you can't find a definition for
that term.  Vulcanizing is done with heat, not fluid.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tube Patching Question
Newsgroups: rec.bicycles.tech
Message-ID: <oQqDb.2905$XF6.67097@typhoon.sonic.net>
Date: Mon, 15 Dec 2003 22:45:40 GMT

Dave Kahn writes:

>> 7.  Remove cellophane/paper (snipping edges in advance makes peeling
>> off possible without disturbing patch; press down again to make
>> sure though).

> Some patches have covers that are very difficult to remove.  Folding
> the stuck-on patch with the cover on the outside of the curve will
> often split the cover making it relatively easy to peel away from
> the patch.  Peeling from the split towards the edge is also less
> disruptive to the feather edges.

Rema, the most commonly use patch here and in Europe, has a cellophane
cover with a prepared break line across its center.  After positioning
the patch, stretching it in the direction that causes the break line
to separate, the cellophane will peal away from the center of the
patch making it easy to remove without lifting the patch.  The break
line is discernible as a faint dotted line on the shiny surface.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Using Tip Top Original Patches
Newsgroups: uk.rec.cycling,rec.bicycles.tech
Message-ID: <6pEzc.16974$Fo4.220687@typhoon.sonic.net>
Date: Tue, 15 Jun 2004 15:16:18 GMT

John B? writes:

>> With all patches, foil side faces tube.

>> Snipping edges of cellophane in advance makes it easy to peel it off
>> afterwards.

> I never bother, as trying to remove the cellophane may lift the edge
> of the patch.

That's why the cellophane is split in the middle... so you can peel it
from inside to outside of the patch periphery with no lift-off.  This
is done by manually stretching the tube and patch so the cellophane
breaks across its barely visible perforations and lifts in the middle.
Cellophane is not stretchable and should be removed to allow the patch
to elastically cover the puncture area.

Aluminum foil is used to keep the 'red' side from losing its adhesive
quality through evaporation.  Cellophane does likewise but being less
impervious, is on the back side of the patch where it is good enough.
The foil is easily removed by bending down a corner by which the
cellophane remains flat and allows pulling the patch from the foil.
Do not cut off the corners because they are there to lift the patch.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Using Tip Top Original Patches
Newsgroups: uk.rec.cycling,rec.bicycles.tech
Message-ID: <LoFzc.16989$Fo4.220808@typhoon.sonic.net>
Date: Tue, 15 Jun 2004 16:24:11 GMT

Mike DeMicco writes:

>> That's why the cellophane is split in the middle... so you can peel
>> it from inside to outside of the patch periphery with no lift-off.
>> This is done by manually stretching the tube and patch so the
>> cellophane breaks across its barely visible perforations and lifts
>> in the middle.

> They should perforate the cellophane in both the x and y directions.
> I have still had the edge of a patch lift when pulling off the
> cellophane from inside to out.  Now, I wait a day for the patch to
> cure before removing the cellophane.

A double split would make removal more difficult because it would
guarantee four pieces.  The time to dry the adhesive is before
applying the patch.  Then pulling off cellophane from the center will
not lift the patch.  At least REMA gave this some thought.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Using Tip Top Original Patches
Newsgroups: uk.rec.cycling,rec.bicycles.tech
Message-ID: <lZOzc.17113$Fo4.221938@typhoon.sonic.net>
Date: Wed, 16 Jun 2004 03:17:37 GMT

Jeff Starr writes:

>>> I never bother, as trying to remove the cellophane may lift the
>>> edge of the patch.

>> That's why the cellophane is split in the middle... so you can peel
>> it from inside to outside of the patch periphery with no lift-off.
>> This is done by manually stretching the tube and patch so the
>> cellophane breaks across its barely visible perforations and lifts
>> in the middle.  Cellophane is not stretchable and should be removed
>> to allow the patch to elastically cover the puncture area.

>> Aluminum foil is used to keep the 'red' side from losing its
>> adhesive quality through evaporation.  Cellophane does likewise but
>> being less impervious, is on the back side of the patch where it is
>> good enough.  The foil is easily removed by bending down a corner
>> by which the cellophane remains flat and allows pulling the patch
>> from the foil.  Do not cut off the corners because they are there
>> to lift the patch.

> Hi, Park tells you to leave the cellophane on, take a look:

http://www.parktool.com/repair_help/FAQGP2.shtml

> See the section that has the heading - Patching an inner tube using
> the VP-1 Vulcanizing Patch Kit

Well, that's because the cellophane on these patches is not split and
pulling it off from the edge will lift the patch.  Therefore, that has
little to do with REMA patches, patches known as the best available.

> I had removed the cellophane the first time I used them and then
> read the instructions.  What do you think?

I think I'll continue to use REMA patches and will remove the
cellophane as REMA sees fit to do.  If you don't, and must use the
tube after patching, the patch cannot expand freely with the tube
whereby the glue joint will be stressed as the tube expands to fill
the tire volume (that is obviously greater than the tube or the tube
would wrinkle on installation).  REMA has been in this business for a
long time and does a good job.

You may have seen previous discussions on how to patch tubes here, in
which it was proposed that if the patch peels off, then the glue was
not sufficiently dry.  You can try that, but even after five minutes
of drying a patch can be pulled off easily by pulling the cellophane
from one edge.  That is why I recommend patching the punctured tube,
using the spare tube that should be in the back-up kit, putting the
freshly patched tube in the back-up kit and letting it cure.

http://draco.acs.uci.edu/rbfaq/FAQ/8b.1.html
http://draco.acs.uci.edu/rbfaq/FAQ/8b.11.html
http://draco.acs.uci.edu/rbfaq/FAQ/8b.13.html

That's enough for tires right now.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: tubes cost to much.
Newsgroups: rec.bicycles.tech
Message-ID: <AcG5e.13884$m31.135825@typhoon.sonic.net>
Date: Sat, 09 Apr 2005 01:28:00 GMT

Benjamin Lewis writes:

>> I also wonder, since the glue is vulcanizing (unless you are
>> talking about so-called "glueless" patches), how much heat it would
>> take to melt the glue.

> I've never tried it, but according to Jobst:

> http://www.sheldonbrown.com/brandt/patching.html

> "With heat supplied by a hot iron or heated frying pan at moderate
> temperature, patches come off easily."

> I have no idea what this would translate to in terms of rim
> temperature while braking, but it certainly sounds plausible that
> this could occur for patches close to the rim.

You can peel them off with care, they do not separate and fall off.
It still takes force but it doesn't tear the patch into little slivers
and leave red rubber lumps behind, the usual result of pulling off a
cured patch.

Brake temperatures only heat the underside of the tube and even there
it is not enough for a patch to separate.

Jobst.Brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: tubes cost to much.
Newsgroups: rec.bicycles.tech
Message-ID: <hKQ5e.13922$m31.136144@typhoon.sonic.net>
Date: Sat, 09 Apr 2005 13:26:37 GMT

Bill Bushnell writes:

>> Brake temperatures only heat the underside of the tube and even
>> there it is not enough for a patch to separate.

> Could you please clarify your statement?

> Are you stating that rim heat due to braking would never be
> sufficient to soften cured patch glue enough to make it leak air
> under pressure?

Pressure is not what makes patches leak in the first place, it is
patch separation and that is independent of pressure as long as it
high enough to ride, the tube being fully expanded to the tire cross
section (aka stretched).  Unless the patch is in contact with the rim,
it won't get heated significantly and even then, it takes a good tug
to separate it from its attachment.  Patch separation occurs from the
tube peeling away from the patch beginning at the perforation.  That
peel force is small if you consider how little force is required to
stretch the tube to the tire cross section, and then consider the
local tension of the arc of that curvature.

> I've experienced a suspicious loss of air on several occasions,
> always on downhills that required significant braking (e.g. Kings
> Mtn. Rd., Vista Verde/Ramona, etc.), always in warm or hot weather,
> and always when using tubes patched on the rim side.

Did you do an autopsy on the patch?  If you did and it wasn't a new
patch, it must have been lifted off before, or it was a freshly placed
patch.  Don't leave this sort of thing to mystery.  Investigate!  It
was definitely not rim heating that caused the failure.  You can
assure yourself of that by using the "heat on the frying pan" method
to remove a well cured REMA patch.

> The symptoms were always the same: several occasions in close
> succession of hard or moderate braking, the last of which would be
> followed shortly by a rapid loss of air, accompanied occasionally by
> audible hissing.  The tube would hold air outside of the tire, even
> when inflated to greatly swollen proportions.  Tubes patched many
> times on the tire side but not on the rim side never gave me this
> kind of trouble.  I stopped having these kinds of flats when I
> starting retiring tubes that got damaged on the rim side.

That is a classic uncured patch syndrome.  The only part of the patch
that is still in place is the rim.  Besides, on the rim side, patch
peel is greater because there are right angle bends at the tire-rim
interface that help peel a fresh patch.

> Do you have an alternate explanation for these kinds of flats?

You mean "this kind of flat" or "these flats" don't you?

http://www.sheldonbrown.com/brandt/patching.html

Jobst.Brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: glueless patches.
Newsgroups: rec.bicycles.tech
Message-ID: <hVs%d.11649$m31.121949@typhoon.sonic.net>
Date: Mon, 21 Mar 2005 05:25:33 GMT

Mike Jacoubowsky writes:

>>> I've been using Aireon glueless patches lately and they work
>>> great. Sick of the glue and only getting 1 out 3 to work.  I never
>>> tried glueless because of the bad rap, until I saw another guy use
>>> them, and couldn't believe how simple it was and the good results.
>>> Are the Aierion's just better than the other brands, why the bad
>>> rap?

>> Because they don't always stick and stay stuck.  3 out of 3 normal
>> patches should work and stay working forever.  You're probably
>> doing something wrong, like not sanding the tube enough, or not
>> letting the glue dry before applying patch, or inflating to test
>> with tube outside of tyre.

> My experience with the thin, pre-glued patches (the ones I use are
> under the Trek label, but they're sold by others as well) have been
> excellent.  They have worked nicely as permanent patches, not
> something temporary that I would have to worry about down the road.
> The big advantage I see to them is that there's no tube of glue to
> dry up... once opened, there's a definite shelf life to the small
> tubes of glue that come with patch kits.

What is less apparent is that tubes of glue do not dry up AFTER they
have been opened, but do so all the time because the makers of this
stuff don't realize that the crimp on the bottom of the tube is porous
and the solvent in the glue, highly volatile.  That's why it dries so
quickly when used.  Bicycle shops with low turnover of stock sell
pre-dried glue tubes.  I have had the opportunity to puncture the
threaded end only to find a veritable void with a little stiff jelly
after squeezing the tube hard enough.

> On the other hand, I had poor results with the much-thicker square
> patches made by Park.

So how well can you pull one of these off after a week in place?  What
makes them "cure" and become permanent as glue+REMA patches do?

Jobst.Brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: glueless patches.
Newsgroups: rec.bicycles.tech
Message-ID: <3JF%d.11716$m31.122222@typhoon.sonic.net>
Date: Mon, 21 Mar 2005 19:59:59 GMT

Mike Jacoubowsky writes:

>> So how well can you pull one of these off after a week in place?
>> What makes them "cure" and become permanent as glue+REMA patches
>> do?

> I don't find any noticeable difference between the peel-ability of a
> Rema vs one of the Trek pre-glued patches.  What is it about a
> standard patch that makes it "cure" as you say, that's different
> from what you might expect from a pre-glued patch?

If you try to remove a REMA parch after a day or so, it doesn't come
off and cannot be peeled off... unless you use heat as described in
"removing patches".  If you can peel a pre-glued patch off with a
fingernail, it isn't as secure as it should be.  Can you do that?

> Doesn't really matter that much to me though, as they (the pre-glued
> patches) seem to work just fine.  I do notice, however, that
> pre-inflation is more likely to cause one to lift an edge than would
> be the case with a Rema, but after they've been used for even a day
> in a tire, they seem every bit as "bonded" as a Rema would be.

Well, that's the question.  They are apparently more sensitive to
preparation and use judging from the number of people who have
reported poor reliability and have cast doubt on them.  Of course
there are also users who have poor success with the glue and patch
method so it's hard to tell.  I have not used them.

Jobst.Brandt@stanfordalumni.org