From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Slick tires worn, how to tell?
Date: 11 Jun 1998 21:07:05 GMT

Jeffrey Fass writes:

> How can I tell if my slick clinchers are worn enough to change?  It
> always looks the same.  I don't want to find out with a tear and a
> crash.

Don't worry that your tires might break open.  Tires do that from old
age, not wear, so it could happen with any tire, profiled tread or
smooth, if you wait long enough.  If your tires are not damaged by
road hazards, they will serve you well until the cords show through
the tread rubber.  In the event that this occurs on your rear wheel,
exchange front and rear tires if you are on a long ride.  Because
front tires wear at glacial rates, this will enable your to finish the
day without incident.  You won't notice additional wear on the tread
bare tire.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question ...
Date: 25 Aug 1998 16:14:01 GMT

Lyle Rooff writes:


>>> I find that I get a lot of tiny little cuts on the tire before I
>>> get even close to having the cords show.  Would you ignore these
>>> little cuts, or would you change tires?

>> If its over a longer period and you ride in the wet, little cuts
>> that penetrate to the casing have a damaging effect on the cords.

> Would this apply to tires with nylon/synthetic cords, or just to cotton?

All bicycle tires.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question ...
Date: 25 Aug 1998 16:32:07 GMT

Leon Gierat writes:

>> Should you be on a longer ride when cords show up, exchange front
>> and rear tires because the tread-bare tire will not wear
>> significantly on the front.  I've done it, it works, while others
>> have tried to finish on the tire only to BAM.

> I'd much rather have a rear tyre blow than a front. A rear blowout
> is usually controllable, a front can send you all over the place.
> The tread bare tyre may not wear significantly on the front, but
> being so thin, will be much more susceptable to punctures.

Oh pshaw.  You won't have a blowout unless you waited too long before
realizing you were in the cords.  A trace of cords won't accelerate
flats either.  I've ridden through so many tires and I have piles of
treadbare tires in the old tire repository.  All this fear mongering
seems to go a long way even though it's based on a bunch of imaginary
hypothetical images of how things work.

> I'd personally never ride a dodgy tyre on the front. If you're tyres
> are getting so thin that the cords may show through on a long ride,
> then it's probably time you replaced them anyway.

So what is a "dodgy tire" anyway?  When I start on a days ride, my
tire may have enough tread that no cords are showing and in the course
of the next 100 miles in the hills it could show some.  At that time
switching tires works fine.  In contrast, not switching has lead to
unnecessary tire failures and a hitch hike to a bike shop or a phone
call for help.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question ...
Date: 26 Aug 1998 16:09:38 GMT

Leon Gierat writes:

>>>> Should you be on a longer ride when cords show up, exchange front
>>>> and rear tires because the tread-bare tire will not wear
>>>> significantly on the front.  I've done it, it works, while others
>>>> have tried to finish on the tire only to BAM.

>>> I'd much rather have a rear tyre blow than a front. A rear blowout
>>> is usually controllable, a front can send you all over the place.
>>> The tread bare tyre may not wear significantly on the front, but
>>> being so thin, will be much more susceptible to punctures.

>> Oh pshaw.  You won't have a blowout unless you waited too long
>> before realizing you were in the cords.  A trace of cords won't
>> accelerate flats either.  I've ridden through so many tires and I
>> have piles of treadbare tires in the old tire repository.  All this
>> fear mongering seems to go a long way even though it's based on a
>> bunch of imaginary hypothetical images of how things work.

> Surely it follows that the thinner the tread on the tyre, the less there
> is for a thorn (or whatever) to go through.

Surely this does not follow.  Flats from thorns go through a road tire
whether it is new or old and so does most glass.  If that weren't the
case, people with new tires would not get flats.  I have not found a
difference in occurrence of flats right down tot the cords showing.

> Haven't you ever used those really cheap inner tubes that are really
> thick, and found something stuck in that hasn't gone all the way
> through? Or likewise, picked bits out of your tyres that haven't
> gone through far enough to cause a puncture.

I'm sure you can come up with a thorn-proof tube scenario that
supports your visualization but we are concerned with tires and how
far to wear them out.  Now you come up with "cheap inner tubes" and
extraneous musings.

> Are you saying that the cords and the casing are the major constituent of
> the puncture resistance of a tyre? If so (and if you are correct), then
> I'd have to agree, worn down tread isn't an issue and it's fine to run a
> tyre with the cords showing on the front.

There is no puncture resistance against objects sharp enough to
penetrate a tire, it's only advertising that tells you that.  Placing
more material between the inside of the tube and the road improves the
odds minimally until you get to thicknesses that make the tire roll
about as bad as a solid tire.  For practical tires, the ones most
people ride, the best flat protection is to watch where you ride.

> I still stand by my statement of preference to have a rear puncture
> rather than a front. (And to have to walk home rather than take the
> ambulance (I know extreme example, scare-mongering - hey, I didn't
> mean it kids...))

The argument was about a blowout, not a flat.  A tire worn to, but not
into the cords, will not blow out.  What you are saying is that you
would rather blow out your rear tire and walk home than exchange the
front and rear tires if you noticed cords showing in spots.  You are
speaking hypothetically, I am speaking from experience.  I assure you
it works.

>>> I'd personally never ride a dodgy tyre on the front. If you're
>>> tyres are getting so thin that the cords may show through on a
>>> long ride, then it's probably time you replaced them anyway.

>> So what is a "dodgy tire" anyway?  When I start on a days ride, my
>> tire may have enough tread that no cords are showing and in the
>> course of the next 100 miles in the hills it could show some.  At
>> that time switching tires works fine.  In contrast, not switching
>> has lead to unnecessary tire failures and a hitch hike to a bike
>> shop or a phone call for help.

> *My* definition of a dodgy tyre is when it's full of cuts in the
> tread, or if there's a sidewall wearing through (usually takes a
> badly adjusted brake, but Contis seem to do it at will!?!), or any
> other signs of wear other than the obvious 'tread disappearance' of
> where the rubber is wearing away.

So what does all that have to do with the question of tire wear?  If
you ride enough that tire wear is a consideration, then tires aren't
years old when they get thin.  What you describe are the tires I see
in the bike stand at work that have ancient tires on them.

> I dunno, perhaps I'm just a wuss, but I really don't like the
> thought of the consequences of having a front blowout when
> descending at speed.

You haven't done this and are imagining it.  It doesn't occur that
way.

> P.S. It sounds as if you know (or think you know) all about tyres,
> please explain and then maybe I won't scaremonger anymore.

I think two things are at work.  People tell these stories that get
better with retelling and the original event is misinterpreted so that
cause and effect is not understood.  Some people are so terrified of
flats from these two effects that they ride solid tires.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question ...
Date: 24 Aug 1998 21:38:38 GMT

F. Hayashi writes:

>>> Is it time to replace my Conti Grand Prix 300 when the profile on
>>> center section of the thread is now flat ?

>> So?  Are the cords showing yet and if not, ride till the cords show
>> up.  Why do you care what the cross sectional shape is?  The tire
>> is flexible and will conform to the road.

> I find that I get a lot of tiny little cuts on the tire before I get
> even close to having the cords show.  Would you ignore these little
> cuts, or would you change tires?

If its over a longer period and you ride in the wet, little cuts that
penetrate to the casing have a damaging effect on the cords.  If you
ride much, tire wear is rapid enough that the casing does not degrade
materially from small cuts.  You can usually see that the cords are
about to show anyway, because there are some high spots that show
first and the cords put a ripple on the smooth tread surface.

Should you be on a longer ride when cords show up, exchange front and
rear tires because the tread-bare tire will not wear significantly on
the front.  I've done it, it works, while others have tried to finish
on the tire only to BAM.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question ...
Date: 31 Aug 1998 15:44:49 GMT

Tom Ace writes:

>>> Why did I get flats much more frequently with tubulars than with
>>> modern clinchers (which I ride at the same pressures that I rode
>>> tubulars at, over the same kinds of streets)?

>> I don't know.  Why don't you tell me.  You were there, I wasn't.
>> I don't experience increased flats as my tires wear thinner.

> I'd be speculating.  I was hoping an engineer with extensive
> knowledge about tires might be able to explain it.  It wasn't just
> me getting more flats with tubulars, it was everyone I rode with as
> well.

Since my riding hasn't changed much over many years, I can say for
sure that I did not get more or less flats with tubulars than the
clinchers I ride now.  The only difference was that some pinch flats
but certainly not all were avoided by having latex tubes.  It was
after all in tubular days (1950's) that I coined the term "snake bite".

> Is it your view that the idea of tubulars flatting more readily
> than clinchers (at comparable pressures) is an unfounded legend?

Yes.  Each rider carried one spare tubular.  It worked.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire Rotation?
Date: 9 Oct 1998 15:15:49 GMT

Steven J. Schiff writes:

> I have a Trek 7500 hybrid bike which I bought new in April.  I've
> got about 1300 miles on it, and I'm starting to see a little bit of
> wear on the tread of the rear tire.  The front tire shows no wear at
> all.  Should I swap the front and rear tires to equalize the wear?

Wear out the rear tire and then switch, putting the new tire on the
front, otherwise your front tire will some day be so old that its
casing fails.  It's best to wear them out by rotation, but do it when
the rear one wears out (to the cords).

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire Rotation?
Date: 12 Oct 1998 15:40:33 GMT

Sheldon Brown writes:

>>> Not if you care about safety.  Put the good tire in front.  I do
>>> this with my car too; when I buy tires, I buy a pair, put them on
>>> the front and move the worn ones to the rear.

>> I agree that the new tire should go on the front but not for that
>> reason.  There is no excuse to ride a tire that is not trustworthy
>> on either the front or rear.  Both will cause a serious crash if a
>> casing failure occurs in a swift curve, the place where Murphy's
>> law predicts for such a failure.

> Tires are analog, not digital, and their trustworthiness lies on a
> continuum.  I'd prefer to have the more trustworthy tire in front.

I disagree.  Trustworthiness has a cutoff beyond which the tire is a
hazard, that being old age cracking, sidewall fraying, or any
distortion of the casing.  I'm sure you can think of others.  I don't
consider a casing failure acceptable on either wheel and that is
digital.  Not that it hasn't occurred.  That's one reason why I am
glad to not be riding tubulars anymore.  There were too many sources
of undetectable failure.

>> That said, in the days when Specialized Touring II was the best all
>> around durable tire, we first rode them smooth and then moved them to
>> the front because the raised center ridge of a new tire cornered
>> poorly.

> This was a special case, and is mainly of historical interest.
> Generally, where wear affects traction at all, it makes it worse,
> not better.  I would always rather have the tire with better
> traction in front.

We needn't have that concern anymore because you can buy tires that
have the best traction from the outset.  Although most people confuse
bald auto tires with slick bicycle or motorcycle tires, slick bicycle
tires have the best traction, wet or dry and do so until the cords are
showing.

>> In those days the tread wore down about twice as fast as today so
>> there was no significant aging problem.

> Huh?  Tires used to wear faster?  Aging "problem?"  Whuzzatabout?

Tires didn't get OLD because they wore out so fast.  Cracked tread and
water intrusion into the casing fibers is a major degrading effect and
one that makes old tires dangerous to ride.

> Sheldon "It's Kinda Academic For Me, 'Cause I Hardly Ever Wear Out
> Tires.  I've Got So Many Bikes To Share The Wear, And Have A
> Weakness For Upgrading To The Newest, Coolest Newfangled Tire Models
> Before I Get To Wear Out The Old Ones." Brown

Then you may not be exposing them enough to the weather for them to
rot on the wheel, but it is a major problem.  It is the academics who
should worry.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire Rotation?
Date: 12 Oct 1998 15:51:32 GMT

Stuart Longhurst writes:

> Jobst, you dont have to go back that far to find tires which are
> very good but dont last, look at the Corratec semi-slick, I wore one
> out in Spain (Sierra Nevada) in just about three weeks.

My point was more to the side that the best and longest mileage tire
available at that time didn't last more than about 2000 miles in the
mountains.  On my summer tour I had to rotate tires just to stay out
of the cords.

You can always find special purpose tires that have minimal tread.
The Avocet TT tire is for TT's.  Using it for touring or stage racing
is not reasonable as are the tires you mention.

> Getting back to tire rotation, although I don't rotate mine, I ditch
> them when they've worn down, a minor factor influencing the
> interchangeability is of course directional threads. Many tires are
> produced for either front or rear wheel use, and not both.

There is no advantage to directional tread.  As I mentioned, the
motorcycle people went through all that in the 1950s gradually
converging on slicks today.  All the directional jive is just that.
No one has measured the slightest advantage.  On the contrary, the
slightest tread patterns have shown a decrease in cornering on testing
machines.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire wear question
Date: 7 Sep 1999 15:46:07 GMT

David T. Blake writes:

> The question this brings up is are the drive forces substantial
> in the wear of the tire compared to gravitational forces ?

Yes.  On several occasions I observed the wear rate of a new smooth
tread tire with mold flash, ridden in the flat in comparison to
climbing long steep hills.  The mold flash goes away rapidly in the
hills but stays around for more than 100 miles on flatland.  Similarly
such a tire wore a visible flat band on a 250 mile tour over the
Sierra Nevada including Sonora Pass with its more than 20% grades.
This distance, in flat riding, just wears off all traces if mold flash
without a flat wear track.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire Wear
Date: 14 May 2000 22:23:59 GMT

Tim McNamara writes:

>> Tire life will depend on your weight and riding style.  But you
>> should expect the rear tire to last only about half the mileage of
>> the front (if that).  I'm 195 lbs and get about 1300 miles from a
>> rear tire.  The life of the front tire is usually determined more
>> by cuts and rot than tread wear.

> Wow.  YMMV I guess.  I am disappointed if I get less than 3000 miles
> from a rear tire... and I weigh 210 lbs.

It also depends on where you ride.  If you ride mostly in the
mountains you'll find tires last less than half as long as in the
flat.  It also depends on how much tread you start with.  An Avocet TT
has about 2/5 as thick a tread as an Avocet Road but have a smaller
cross section.  Lets compare riding on various terrain with the same
tire.  Typically, I put on more than 2500 miles in the Alps with an
Avocet Road rear tire before it gets close to wearing through, whereas
I formerly used Specialized Touring II tires that required rotation on
the same rides and were both bare.  Today most riders in this area use
colored tires that wear out even faster.  They wouldn't be seen on an
ordinary tire or rim for that matter.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.misc,rec.bicycles.tech
Subject: Re: Avocet tire wear question
Date: 1 May 2001 15:45:44 GMT

David L. Johnson writes:

> I've been using Avocet Fasgrips for about a year now, and think they
> are the best thing since sliced bread.  But I have a question about
> determining when they are worn out.

When the cords begin to show you have another 50 miles if you don't
happen to be climbing a long steep hill.  However, before that you can
see a different shade of black rubber becoming visible down the center
of the tire.  This is the "prime" coat that prevents "Firestone" tread
delaminations, the layer that Firestone chose to not use.  About 100mi
after the prime coat shows, cords or their location will become visible.

> One tire, a 25mm 20K (Kevlar belt, wire bead) which has been on a
> rear wheel all its life, seems to be showing a second layer of
> rubber.  When I saw this clear boundary appearing, near the middle
> of the tread, I thought it was wearing through to the Kevlar
> (especially in one area that was the result of a skid).  I took the
> tire off and shined a light from the other side, and it seemed that
> there still was rubber left.  The "second layer" that is showing
> through now for close to half way around in the center of the tread
> feels like rubber, looks like rubber.  It's maybe slightly darker
> than the rest of the tread.  No fabric visible yet.

You're getting close.

> Is this tire worn out, or can I trust it a bit longer?  I would
> guess it has somewhere between 3,000 and 4,000 miles on it.

You've been riding in the flats too much.  Climb more hills and you'll
find they last about 3000.  Before these tires, I use Specialized
Touring II tires that I had to rotate on a 2500mi trip in the Alps to
finish with two tires with cords showing.  Now, with Avocet Road 20's,
I don't rotate and make the whole trip.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.misc,rec.bicycles.tech
Subject: Re: Avocet tire wear question
Date: 2 May 2001 00:01:41 GMT

Dave Chen writes:

>> You've been riding in the flats too much.  Climb more hills and you'll
>> find they last about 3000.  Before these tires, I use Specialized
>> Touring II tires that I had to rotate on a 2500mi trip in the Alps to
>> finish with two tires with cords showing.  Now, with Avocet Road 20's,
>> I don't rotate and make the whole trip.

>> Jobst Brandt      <jbrandt@hpl.hp.com>

> M.r. Jobst, could you explain the mechanism behind tires lasting
> longer on the flats vs. hills?

Make that Mr. Brandt or Jobst, lest we get conflicting uses of my name.

When climbing, especially when standing, the rear wheel slips on paved
roads, something that becomes more apparent on gravel roads, where
complete wheel spin can occur during the power pulse that occupies a
relatively small part of the pedal stroke.

Another way this should be apparent is that front tires wear at less
than half the rate of rear tires and it is not proportional to load
either.  The same is true for car tires.  On rear wheel drive cars,
the rear tires wear noticeably faster than front tires.  Front wheel
drive exacerbates that problem greatly in that all cars do most of
their braking with the front wheels and steer around curves.  Adding
the propulsion to this makes rear tires wear far less than half as
fast as front tires on such cars.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Tire Resistance Ratings
Date: 3 May 2001 17:58:09 GMT

Stephe Thayer writes:

> I'm I the only one that finds it odd that the Avocets have ALL the
> lowest rolling resistance on this chart and that also just happens
> to be the company Jobst works/worked for?

The tests were performed in Japan by the rubber institute and Avocets
are not the only low RR tires.  As I pointed out, if the tubulars had
been mounted with hard glue, they would have been even lower, as one
would expect from the thickness of the tube, casing and most
importantly, tread.  After all, flexing of elastomers is where RR
occurs and at the time of these tests, Avocet was the first to use
a new thinner but more durable tread rubber made by IRC.

It was the introduction of this rubber to bicycle tires that increased
tread life greatly while also improving traction.  That was the
incentive to make the picture of high speed cornering to show that
this tread has good traction and that slicks corner well.

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

The age of these tests and the picture is apparent from the old toe
clips and straps.

The pilot run of these tires suffered from Firestone delamination (and
probably for the same reason) because the new compound did not adhere
well to casings.  The solution IRC found was to make the tread of two
layers, the first, a thin layer of the old tread rubber that is
inferior but adheres well to casings, and the second the wear layer
that adheres well to the old rubber.  Firestone/Bridgestone seems to
have not chosen this costly step without success.  The two layers turn
out to have another benefit in that it gives a warning that there is
about 100 miles of tread left when the color changes.  Both rubbers
are black but distinguishably different in surface texture.

What should be noted is that no one has made subsequent RR tests that
are anywhere as comprehensive and inclusive of tires on the market.  I
suspect there is little interest in the subject from what I see on the
road.  Fashion is far more important to the current market, so why
belabor the subject of functional differences between tires.  That's
not where it's at.  No one gives a hoot that colored tires have poor
traction, especially in the wet, and that they wear out fast, but they
cost more to make up for that.

Jobst Brandt      <jbrandt@hpl.hp.com>