From: praetzel@maxwell.uwaterloo.ca (Eric Praetzel)
Subject: Re: Team Motorola will Race on Clinchers in 1993
Organization: University of Waterloo
Date: Fri, 8 Jan 1993 17:34:46 GMT

In article <3450015@hplred.HPL.HP.COM> jbrandt@hplred.HPL.HP.COM (Jobst Brandt) writes:
>   [regarding different tires]
>I don't feel a big difference although I find the wear out rates
  Dito.  I can't say that I have felt any differences between the various
  tires (tubular or clincher) that I have ridden on.

I just did a bunch of measurements on various Conti's, IRC and a few other
tires I had laying around.  Tires like the IRC Triathelon were supposed to
have an "oval" cross section.  My ass. Since everyone lays their cords pretty
well the same way the result is that they are all pretty well circular.  The
measurements bore that out.
  How on earth could anyone attribute ride characteristics to the casing?
You are talking about something that results in a fraction of a percent of
the total loss and then you are talking about small percentage changes in
that.  Terry is relying upon his butt in this case but how do you expect to
feel a one part in > 1000 change?  There may be accustical changes but thats
about all.  If you change the pressure by 1% you will change the "feel" of
the tire much more because that is on the order of 1% and not fractions of
a hundredth of a percent as in the casing.  So you have to agree that shape
and casing are insignificent at best.
  Getting back to the differences in strength of a tubular vs clincher because
of the rim.  So?  The wheel is a tension structure.  Since the spokes are the
same and the same tensions are used the wheels have equal strength.  It is not
all that dependant upon the rim.  This reminds me of how much "stiffer" aero
profile rims are.  Yes they are on paper but by the time you build the rest of
the wheel around it you will not have much if any difference (yet again some
people claim to feel it).
  As for comparing different tires on different courses.  Good luck.  To test
a tire the _only_ reliable way is on a machine.  It has been documented over
and over than man is a poor judge of anything and when you are riding a bike
how do you know what to attribute to the frame, bars, saddle, human flesh,
tires, wheels, processing in your wetware or external sounds .....?  I am not
in a mood to go argueing that.  But the variety of opinons only reinforces 
that evidence as far as I can see.  Others will try to use that to prove that
the machines are not measuring what our senses are.  Well it certainly is not.
But the machine measurements are repeatable; day after day after day.  That 
can not be said for human perceptions.
  So if you feel that your tires are holding you back.  Go ahead.  Spend 5*
as much and get the top of the line tubies with whatever rim happens to be
_the_ rim this week, and don't forget those very important spokes and nipples.
The fact is that you are playing with fractions of a small percentage.  Feel
it?  Ha.  Notice it?  Can you determine which part of your coast down is due
to air drag and which is tire drag?  Dream on.
  - Eric 
>slightly different.  I used the larger cross section versions and
>ride Avocet ROAD (non K and steel bead).  These last plenty long and
>have all the other characteristics that appeal to my liking besides
>being offered by Avocet free for the testing.
>
>> I have noted that Conti's have a _much_ stiffer ride and have
>> written this down to the shape of the tire (Conti's are
>> elliptically shaped and Michelins round.)
>
>I don't believe the cross section of the tire is any different from
>any other equivalent quality tire.  They are all round.  There is
>nothing in the casing that would let it inflate to any other cross
>section such as a structural belt or variable cord angle.  The side
>walls are no stiffer than the way they feel when deflated and that
>isn't much.
>
>> It would seem to me that handlebar mounted accelerometers couldn't
>> miss the difference since it is so pronounced.
>
>I think you will see more of such tests with Specialized using such
>a measurement to promote their tires and suspension.  It is sad that
>Bicycling is so advertising bound that they are afraid to test
>anything.  With their budget and staff they could be a leader in
>qualifying new products rather than letting the market decide at
>great customer cost.
>
>jobst_brandt@hplabs.hp.com