From: praetzel@maxwell.uwaterloo.ca (Eric Praetzel)
Subject: Re: Team Motorola will Race on Clinchers in 1993
Organization: University of Waterloo
Date: Thu, 21 Jan 1993 13:10:58 GMT

In article <1993Jan20.213657.28021@hpcvusn.cv.hp.com> harry@cv.hp.com (Harry Phinney) writes:
>praetzel@maxwell.uwaterloo.ca (Eric Praetzel) writes:
>: A good double blind
>: experiment would show you that what you attribute to tires is complete 
>: delusion.
>
>Now this is a good, unbiased sort of attitude to take into testing.  You
  Please.  Say that with a smilie.

>This is not entirely true.  In a criterium you get to know each corner
>quite well.
  Gee.  I just get dizzy.
  From what has been posted I would begin to think that changing the tire
  would give miracilous traction.  When I slide or things get skittish I
  put it down to a change in the pavement and not inadequacy of the tires.
  Then again I would also blame myself for having different velocity/
  acceleration, position.  The tire comes well after all of those.

>:   Again.  I question everything your experience.
>
>That's fine, but I think it's also reasonable to question the
>applicability of scientific results that don't match people's
>perceptions.  It's certainly possible and quite likely that the
  But for the most part I know that I can not trust what someone
  remembers.  Firstly there is misatributation of their senses and then
  there are all of the usual selective memory and malliable memory problems
  that plague any data using a human as a record keeper of sujective data.
  Certainly you have seen the data on subject perception of how hard they
  are riding compared to the actual power they are putting out or the
  fraction of their VO2 max.

  Yes it might be fine to use human preception but there are too many vaiables.
  How do you rate a tire when you are concerned with lots of transient
  responses that can not be quantified.  Can you say that one tire is better
  because it gripped on sand slightly better and yet was only slightly worse
  on a tar patch test?  From the weekly ITTs a club I was in did, I could only
  conclude that the fast riders were faster.  When I look at it I could not
  begin to predict a persons time, given their past data and given several
  people having done the flat out_and_back course within 10%.  I would expect
  the differences between tires to be much less than 10% and since I doubt that
  someone could reproduce a run thru a course identically (within < 10% - not
  average time but same speed, acceleration everywhere).

  Yes there may be slightly differences.  However, that is not borne out by a
  cornering test on said machine.  This would seem to indicate that the riders
  are not very consistant and not the other way around.  Of course we could put
  accelerometers on the test rider and see what is really happening.  But I 
  would not even bother because there are just too may variables (road surface
  inconsistancying being one).


>case.  The situation could be similar to comparing total harmonic
>distortion numbers for audio amplifiers.  The numbers may not tell the
>whole story.  The numbers are correct, and are scientifically derived,
  No but if the distortion is low enough then you are not going to hear it.
  Again in that case changes in humidity, air pressure, temperature can
  change the velocity of propogation by so much as to make any accurate 
  design laughable.  They are hearing something but I would hesitate to put
  the pin on the distortion of the amplifier.  A better example would have
  been violins and their tonal coloration.  But from what I saw about 10
  years ago people are getting that down to a nice science too so that you
  do not need someone with an accomplished ear to tune one as it is being
  made.

>Does anyone care how tires behave on the
>machine?  Only if there is a good correlation between the machine
>results and the results gained in "real world" use of the tires.  In
>other words, is the machine a good model of reality?  How do you
  That is the true test.  But I would never begin to trust a riders' beliefs.
  First I would like to see what one can do with a good accelerometer just
  to see if there is any consistancy between what the rider thinks and what
  really happens.

>But then you go on...
   Yes.  I love it soo much.  I really have nothing better to do with my time.
   After all its been snow and ice for months and there are months to go.
   Luckly for all those involved my computer is experiencing memory and
   keybd problems and I am tiring of this topic.

>I don't feel a significant difference in stiffness and lossiness of the
>sidewall between 18c and 25c clinchers.  Do you claim that one cannot
  Given car tires of that size difference you would feel one heck of a
  lot of difference when going into a corner and in the transient response
  while cornering.  The funny thing is that nobody seems to say similar
  things about bike tires.  But then some simple side load tests will show
  you that the sidewalls of a bike tire do not contribute to the handling
  like they do on a car tire.

>I think you should try some English spelling and grammar work before you
>comment.  Frankly, you could stand to adopt a more civil tone while
>you're at it.
  Yes I agree.  That posting was gratitous and fun.  However, all of these
  opinions are flying around without any good founding.  Naturally that 
  drives me harder to the measurement side of life.  It all reminds me of
  Gary Hooker doing his tests with the Power Pacer.  The riders apparently
  kept their pulse within +/- 1 bpm.  Of course if they would have done a
  comparison using a real ECG they would have noticed that all commerical
  HRMs are only accurate in the steady state and can easily misread by +/-
  3 bpm over the space of a few seconds.  But being a good engineers they
  trusted the power measurements so the HR measurements were there just to
  keep the riders busy looking at something.

  Obivously we can resolve nothing this way.  I just hate to see people 
  say or imply that such "measurements" have anything to do with science
  when they should know better.

  - Eric