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Re: GRM Tire Test

To: Brian Priebe <priebe.4@osu.edu>
Subject: Re: GRM Tire Test
From: Scott Johnson <sjohnson@kcnet.com>
Date: Wed, 13 Jan 1999 11:36:27 -0600 (CST)
On Wed, 13 Jan 1999, Brian Priebe wrote:

> I do not think the course mattered as much.  Any autox couse you will be
> sustain alot of lateral G's, compared to acceleration G's.  SO if is a skid
> pad or if it would have been four 90s in a row I do not think it would have
> changed the results.

I'll take your opinion on this since you were there (and a much better
driver than me), but my impression from viewing the map of the course was 
that acceleration, braking, and transient response weren't as important on
it as they would be on a what I deem a 'typical' auto-x course.

> The 15s were at a width disadvantage but I do not think the width would have
> made up all the time difference on my times.  Yes this course might not be as
> long as some of our courses, but all you have to do is percentage out the
> margin to what you think would be adequate.  I think on the course used a
> tenth was much harder to get than on a typical course, since it was short.
> So in your mind it might help to think as a tenth more like two tenths.

Hmm...maybe 17's really _are_ faster. 

> I am not an engineer, but a tire turning more slowly I would assume has more
> capablility to pull lateral G's, I would assume would be a factor.  You have
> picked on some obvious factors, but there are more factors involved also in
> my opinion.

I'd love to hear from a tire engineer on this. I always assumed that as
long as the footprint was nearly the same, that lateral grip would be
nearly the same. A smaller diameter tire would heat up faster though, a
plus for auto-x.

> You may know more than me from talking to him, but it just rest assured at
> least in my mind that he was not hindering himself compared to the 13s, 14s
> or 15s.

I haven't talked to him, I just remember trying to figure out why he went
with that size.

-Scott Johnson 
 sjohnson@kcnet.com


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