re: tires for autocross, oh my

[Tessie McMillan <tessmc@domain.elided>]

Mars and Uranus are somewhere in my solar chart this week, so all of a 
sudden I'm feeling opinionated... &:-) Anyway, I personally think it's 
unwise to state that for all given tires of a certain compound that they 
will behave a certain way (i.e., they only take a certain number of heat 
cycles, or they are lousy in the rain, etc.) and therefore do or don't 
buy them because of this or that. If it's not a competition autocross 
event where tires will bump you into a higher performance class, some of 
the discussion of R1s is pretty moot, anyway.

If you talk to the manufacturer's reps or go to the web sites you can see 
there are specific differences between the different brands of tires for 
one given compound (say, R1s). Some tires are intended for rain, and some 
are better for dry. If you take a treaded rain track tire and shave it, 
it will behave quite decently in the dry. Some tires behave very very 
decently on one kind of car, but only marginally on a car with a 
different engine location and weight distribution. You can drive the 
heck out of your track tires, cord them, and never exhaust them by "heat 
cycling", although you can also let your tires sit in the garage for 5 
years and they could become worthless grip-wise. There's a lot more 
that can be said about R compound tires.

Also, maybe I don't get out much, but I've never heard of a "not a track 
tire, it's an autocross tire". It's been a few years since I autcrossed 
regularly, but the folks I autocrossed with used the same tires at 
autocross events as they brought out to the track. We used to run a 
smaller diameter wheel on our car (and hence had a different size tire) 
when autocrossing, but we never used a different compound tire. Can 
someone amplify what is meant here?

I've autocrossed on street tires and on track tires, and the driving on 
either is just a different experience to me. If you compare a used street 
tire to a used track tire, the track tire is still going to stick better 
because the compound is designed for grip at a higher temperature.
However, if the track tire has no tread it is not going to grip in the 
wet because there are no grooves for the water to be expressed away from 
the tire. I do wish to point out that if you only have two tires, this 
doesn't do you much good. On any of the cars I've driven, you need four 
matching tires, although they don't need to be the same size. When 
autocrossing on street tires I've found I need to drive much more smoothly 
to go fast. On track tires, I can accelerate and brake violently, so I can 
be much more aggressive without losing time to sliding. Personally, I 
think street tires would be perfectly suited for Alfa spiders anyway 
because of the inherent flexibility of the car. (This is just a 
supposition; I've only autocrossed in a 911.) I don't think it is possible 
to drive an Alfa spider "violently", although I do think it is quite easy 
to drive one "aggressively."

If you are not serious about autocrossing, or are not autocrossing in a 
conference for points, I think the discussion about which tires to run is 
kind of pointless! One can save a lot of money if you "run what you brung" 
and you can have a lot of fun that way. It's not until you're in a 
conference situation that the change in tires can bump you up into a 
different performance class, in which case, why would you be quibbling 
about a couple of useless street tires vs. a couple of aging track tires 
--  you'd want to go out and buy four new track tires and heat-cycle them. And 
then you'd prolly be modifying your suspension, brakes, seating, going to 
lighter wheels, taller tranny, etc.... Am I right?

I guess I should mention all this is moot if it snows....

Tess

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