From: harry@cv.hp.com (Harry Phinney)
Subject: Re: Team Motorola will Race on Clinchers in 1993
Organization: Hewlett-Packard Company, Corvallis, Oregon USA
X-Newsreader: Tin 1.1 PL4
Date: Fri, 22 Jan 1993 00:42:11 GMT

praetzel@maxwell.uwaterloo.ca (Eric Praetzel) writes:
:   Please.  Say that with a smilie.

I assumed you would be able to detect the sarcasm, and I appear to have
been correct.

:   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.

But will all tires slide under exactly the same conditions and at the
same rates?  I certainly don't know.  I'll trust Jobst's machine enough
to accept that the differences in ultimate cornering force may indeed be
insignificant, but that does not prove that the tires behave identically
in every way.  For example, it may be that some riders prefer tires
which have equal or less cornering power but a gentler break away point.
It seems more likely to me that the riders are misattributing real
differences to differences in ultimate traction, rather than there being
no real differences.

:   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, and I also know that well trained individuals can maintain their
effort level within a couple percent of their AT without the aid of a
heart rate monitor.

:   How do you rate a tire when you are concerned with lots of transient
:   responses that can not be quantified.

There is no physical barrier to quantifying such responses.  It may be
complex, time consuming, and expensive well beyond reason to make such
measurements, but it is certainly possible.

:   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?

Do you necessarily have to declare one better than the other?  Knowing such
differences might be interesting.  Then again, the differences may be so
minor as to be insignificant.

:   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.

Or it might indicate that the machine is not measuring the qualities
that the riders are detecting, or it is not measuring them with
sufficient resolution.  We don't know.  Your earlier proposed double
blind testing could settle part of that question, but the existing
machine test results cannot.

: >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.

It appears my point was unclear.  Yes, below a certain level you're not
going to care about THD, but THD doesn't tell the whole story.  Two
amplifiers with identical THD numbers can indeed sound different (yes,
in double blind tests) because there are other factors (e.g.  IM
distortion) which affect the sound.  What Jobst's machine appears to
tell us is that tires do not differ significantly in ultimate cornering
power.  If we accept that then let's determine the source of the
differences which many experienced riders detect.  Perhaps you are
right, that it's their imagination.  Perhaps Jobst is right, that it's
the sound the tires make.  Perhaps I'm right, that it's the sharpness of
the break away.  What I'm saying is that I would be interested in
knowing this, but you appear to be saying that Jobst's machine shows
that all tires are equivalent, so we should close the case and go on to
measuring things other than tires.

Harry Phinney   harry@hp-pcd.cv.hp.com
Newsgroups: rec.bicycles.racing