From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: slicks vs. treads for road bike
Date: 8 May 1999 22:50:32 GMT

Marco (who?) writes:

>> So pick just about any tire with a high tpi count for durability
>> and puncture resistance,

> Would you say WHY you think this.

> Finer threads are weaker threads. They cannot be more durable ( look
> at the Conti sidewall comments posted all the time for starters )
> and cannot be more puncture resistant unless the tread is stronger
> with more resistant rubber components holding it into a casing.

I think you'll find that high TPI tires have uniformly higher burst
pressures than the "kite string" tires.  There may be exceptions but
the fine cord is usually a higher strength fiber than the fat cord
cheap tires.  The fine threads make a far thinner casing that flexes
with little losses.  This is apparent from rolling resistance curves
that show high TPI tires have low rolling resistance and are
relatively unaffected by inflation pressure (lots of flex to little
flex).  You can draw your own conclusions about individual brands and
their side wall failures.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Threads per inch / tires?
Date: 13 Sep 2000 15:51:51 GMT

Andrew Wilks writes:

> But it's not counted like TPI for sheets or other fabric goods.
> Tire manufacturers counts all the threads in all the layers in the
> middle of the tread. So 240 TPI is probably 3 layers of 80 TPI
> material. Most tires are 3 layers under the tread. The cloth loops
> under the bead in a U shape and then each side folds over the center
> tread section.

I don't know on what tires you are basing this but good bicycles tires
are two ply with an overlap of the end plies under the tread to make
that zone three ply.  However, the TPI refers to the threads per inch
in one ply and because it is not a weave but a parallel layup, TPI is
the inverse of the thread diameter.  Therefore 240 TPI = 0.004"
thread.  I don't know of any tire that uses such fine thread and I
have seen many fine silk tubulars.

You might want to check:

http://draco.acs.uci.edu/rbfaq/FAQ/89.html

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jobst.brandt@stanfordalumni.org
Subject: Re: DOUBLE TIRE GRIP REDUCE ROLLING FRICTION
Newsgroups: rec.bicycles.tech
Message-ID: <gk4P9.57441$Ik.1850012@typhoon.sonic.net>
Date: Fri, 27 Dec 2002 22:17:48 GMT

G? Daniels writes:

> An additional question was did anyone decide to run more durable
> tires than the 'silks' and did the heavier carcass reduce speeds or
> increase finishing probability?

This is not conjecture.  Silk is stronger than cotton, the alternative
fiber, and latex, the elastomer with the least hysteretic losses
adheres well to both of these natural fibers (in contrast to Nylon or
Rayon).  With greater tensile strength finer silk threads can be used
(higher TPI) to make thinner two ply casings.  Thinner casings have
less flexural losses than a thicker casing, that is they flex more
easily as we know from experience with materials.

Failures among tires are almost exclusively from punctures with sharp
objects.  This has nothing to do with thin casings but primarily with
thin treads.  Therefore, laying the blame on silk tires is misplaced.

> The newton people previously formulated centripital rotating mass as
> more or less inconsequential visavee Colorado cyclists' eye-popping
> wheel/gram $ photo layout while here we see people once riding on
> delicate/DNF prone tires to take off a few grams.  Amazing!  but
> reasonable?  Or was this something "everyone else does it"

What is "formulated centripital rotating mass" and what does it have
to do with tire durability?  Had you ridden in the days of tubulars, I
believe you would not make such claims.  Most alpine passes were
unpaved and flats were less common than today for lack of bottles
thrown from cars.  You must be vis-a-vis kidding.

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

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tubular rim glue ???
Newsgroups: rec.bicycles.tech
Message-ID: <W7c3c.7171$_3.94289@typhoon.sonic.net>
Date: Tue, 09 Mar 2004 04:56:22 GMT

Carl Fogel writes:

> So here's a truly ignorant question: compared to silk or cotton,
> would Kevlar be better, worse, the same, or impossible?

No.  Kevlar has high losses and does not adhere well to inter-ply
casing elastomers.  This was first discovered with Kevlar belts to
prevent flats.  If the belt is thick enough to do much good, the tire
performs like a slug.  That is why Kevlar belts don't do much good,
they being made so thin to leave some life in the tire.

Silk has far more strength than cotton because the filaments are many
times longer that the longest filament in a cotton boll.  Cotton
relies partly on filament overlap and friction to give its thread
tensile strength.  Silk can do that with far fewer filaments because
they are so long.  Thin casings that could hold high pressure were two
important features of silk tires, and of course the resulting weight.
These tires were truly paper thin.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: Tire casing differences
Newsgroups: rec.bicycles.tech
Message-ID: <kxfb8.197$hb6.1403@typhoon.sonic.net>
Date: Fri, 15 Feb 2002 21:59:44 GMT

References: <a4hmfc$ben$1@newton.pacific.net.sg>
Organization:

Soon Chung writes:

> Most of you must have noticed the advertised differences in the
> casings of different brands of tires but how do the differences
> translate to the real world?  Do high thread counts really mean
> lower rolling resistances? What difference do materials used make?
> Some use cotton, or poly cotton, or pure synthetics.  Silk?

Thread count is an inverse way of telling you how thin the casing
plies (2 - 3) are.  For instance 65TPI is 0.015" thick because that is
the diameter of a single thread.  The thinner the casing, the less
losses it has when flexing as it rolls through the compressed part of
its rotation at the road.  The stronger the thread, the thinner it can
be and still hold the pressure.

Most synthetic fibers are stronger than cotton.  In the days of yore,
tubulars using silk were the thinnest and toughest but then we don't
make parachutes of silk anymore either.  Silk has its benefits though,
because latex rubber, the least lossy, adheres to silk and cotton
while synthetic fibers often need a primer so that when the tire is
molded, the tread will remain attached to the casing and the casing
plies will remain in tact.

As you see, Bridgestone-Firestone did not solve this problem
adequately for the newer tread compounds that, when introduced on
bicycle tires (IRC/Avocet), doubled tread durability although it did
not adhere to the casing.  For this purpose, IRC discovered that
putting a thin false tread of the old rubber on first gave the wear
tread solid hold.

At that time, I began noticing cars pass me with tread separation,
making that slap-slap-slap... sound.  I mentioned this her in this NG
but should have sent some e-mail to the tire makers, but then they
didn't want to hear about it anyway, IRC being auto tire makers as
well.

> What about the Pariba kind of casing: according to their website,
> the casing they use is like a flat tube/sock, as compared to
> separate/distinct fabric layers joined by rubber.

I don't know how they join the ends of this tube but is makes sure you
cannot repair such tubular tires, but I think we are discussing
clinchers and I can't find any Pariba tubulars on the net.

http://www.vredestein-bike.com/pariba/

What advantage do they claim for this process?  I notice they have an
oxymoron "High-tech design manufactured by hand".  What's the "by
hand" got to do with it?

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