On Fri, 16 Aug 2002, Lozano's wrote:
> Hello,
Hi.
> I am hoping someone can recommend tire pressures for my 6 to go autocrossing.
Kool. A "can of worms".
As you may discover, tire pressures directly effect "feel". Some folks
like things "soft" and some don't. (Notice that I didn't say some like
things "hard" for obvious reasons.)
:-)
> After two years of trying to figure out what was causing my rubbing problem,
> we finally looked at the setting of the Koni adjustable shock. To make a long
> story short, it became a finger pointing situation..."I thought you set" "NO!
> I thought you set it".
MAKE A CHECKLIST. Then you will not have this problem. If you are racing,
you can never assume anything. Check, check and re-check. Read the book
"Prepare to Win" by Carrol Smith.
Bob Tullius is reported to have used a _four page, single spaced_
checklist before every race. As you can imagine, this lead to the
team consistantly _finishing_ and because the cars were developed so well
they consistantly were leading while finishing.
> Anyway, the rubbing is finally gone and we are ready
> to go autocrossing. I have 215x55x16 Kumho tires and I do not know what
> pressures to run.
Well, you didn't tell us which Kumhos you are running. But the following
works for most tires.
1. check the sidewall for the highest rated pressure.
2. chalk or shoe-polish your tire's sidewall to tread interface.
3. Fill the tires to the highest recommended pressure and make a run.
4. Did the tire "roll-over" get into the sidewall? If no, go 5, if yes, go
back to 3 and add a bit of air. Use 2 pound increments until you eliminate
the excessive tire roll-over.
5. If you did not get roll over to the sidewall, you might have too much
air! This is rare in autocross, but not outside the realm of
possibilities. Try reducing the amount of air a bit. Try 1 pound
decrements 'till you get roll-over or near roll-over.
6. It turns out that some tires (I have no experience with Kumhos) react
in a very sensitive manner to tire pressure. The Hoosier DOT radials that
I used to use react to 1/2 pound pressure changes... literally "Formula
One technology". But getting the gross tire pressure values can be done
with chalk/shoe-polish and some iterative runs.
7. When all else fails (actually, probably before you start the iterative
process), ask the tire manufacturer for some base-line tire pressures.
They will tell you. After all, they don't want their tires too look like
really bad performers out there.
Note: if you use your autocross tires to drive to/from the track, you
should make sure that you bleed the air from the tires to below the
highest recommended pressures before you drive home... we don't want to
have any wierd handling problems on public roads!
Side-note: Tire gauges can be a problem To eliminate theis problem, buy
at least one good tire pressure gauge and use it for the entire season. If
you switch gauges mid-season, you _will_ have problems unless you can
calibrate the gauges equally across the entire range of pressures. I
learned this one the hard way and spent half a season chasing down
handling problems that were really tire pressure problems! The idea is
consistancy.
Finalt note: no tire is perfect. You can only tune so-much before the tire
becomes the critical factor. If the tires that you are using are really
street tires, then you will not get the ultimate performance that you
might get if you are using real race rubber. Keep this in mind - even with
some of the amazing street tires that are out there now.
> Thanks
>
> Jorge
regards,
rml
------------------------------------------------------------------------------
Bob Lang Room N42-140Q | This space for rent
Consultant MIT unix-vms-help |
Voice:617-253-7438 FAX: 617-258-9535 |
------------------------------------------------------------------------------
/// triumphs@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|