NJTom2000

I've got a combo autocross / drag race thing this weekend. I have to use the same tires for both. I'm going to use my R compound Kumho autocross tires to make sure I end up in a good place on the autocross portion.

Last year I tried and I couldn't get any grip on the 1/4 mile with the R compounds ( last year I used really worn Pilot Sport Cup's for this event ). The tires spun and spun.

R compounds have really stiff side-walls to handle lateral loads. They don't seem to grip well on hard launches.

I'm no drag racer, but with all of the wheel spin I encountered last year I couldn't break into the 14's. If I can find a way to get to the mid 14's I should have a decent shot at winning this thing.

Any Help?

Thanks -- Tom

TubeDriver

Just lower the tire pressure down to about 20-25 psi cold for the drag event.

NJTom2000

I tried lowering the pressure last year on each run but it didn't seem to help. I eventually was down into the 18-20 psi range.

Someone mentioned to me that lowering the pressure on tires with such a stiff sidewall doesn't really help. In fact it may hurt. The tires could have been cupping. Any possible truth to that?

I should have a couple of practice runs to mess around with so I'll try lowering the psi and raising the psi to see what works out.

Thanks -- Tom

Penforhire

Not sure about your particular tires but on Goodyear F1SC's I don't go below 22 PSI to avoid steel-belted damage (on a Z06). Not likely a problem with race tires.

Your problem is probably more temperature related. Auto-x tires are designed to have max grip quickly since tires don't get much heat in 'em at the start. However they get greasy if too hot (notice all the guys spraying water on 'em in between later runs). They have a bit of a narrow operating range. Maybe you're running too hot or too cold when you're staged. Do you do a real burn-out? If so, you might spin 'em less. Do you go through the water box? You have to avoid that on street tires but I'm not sure about auto-x compounds.