It's been a couple of years since I took the NSX out to auto cross. Any suggestion on starting tire presures for auto cross? I have stock 15"&16" wheels.
What tire presure for autocross?
- Thread starter allstar
- Start date
Start 'em out at about 5 psi higher than the high end of a normal street setting ... probably about 41 psi, maybe as much as 45 psi. Then check them during the day so they don't go too much higher.
Better to be too high, though, than to roll over and scuff up and wear out the shoulders.
Better to be too high, though, than to roll over and scuff up and wear out the shoulders.
allstar said:
It's going to depend on the tires, their size and your alignment.
If you have a sane tire width, and the tires are not considerably wider than stock, you'd want to be up around 35-40 PSI cold, possibly even higher, with no more than a 2 PSI split front to rear.
If you have an exceptionally wide tire on the stock wheels, you'd want to go up a few PSI more.
If the surface has very poor grip, go down a few PSI. In general, the higher the grip the higher the PSI you'll need.
Make adjustments from your starting point no more than 2 PSI at a time, and if possible, change just the front or the back, but not both, so you know what kind of effect it's having, unless the car's skating around both understeering and oversteering.
In general it's better to be slightly overinflated than under.
I'd start 38F, 40R and go from there.
dquarasr2 said:
Without considering tire type and grip, I always thought that if you lower the tire pressure, you get more traction in general. That means you would want the tires to be slightly deflated to account for the increase in temperature after several trips on the course.
SilverOne said:
No, not so.
True for drag racing that lowering pressure will afford more traction, which is why you'll see drag tires around 12 PSI. But for left-right and traction, important is sidewall deflection. Too little air pressure allows the tread to fold under, even exposing the wheel to the pavement.
That said, assuming you didn't refer to drag racing convention, what you say is true, that we'd need to account for the increase in PSI due to increase in temperature. However, still, we'd need much higher PSI for performance driving compared to street driving. Typical autocross pressures would wear out the center of the tires tread if driven on the street all the time, 'cuz you wouldn't be exercising the sidewalls at maximum g loading.
For sustained high-speed driving, like one would encounter at a race track with repeated lap-after-lap driving, where the tires get in the 190-210 degree range, true, you'd need less than autocrossing, where tires usually don't get as hot during 40-70 second lap runs. But even so, race track pressures are higher than street, and autocross pressures are higher still by a few PSI.
Hope this helps.
good info, thanks!!! 
Hgher pressures generally provide more grip in autocrossing, up to a certain point. Once beyond that point, the tire crowns and rounds out and you lose contact patch, as well as losing the ability of the tire to deform to the shape of the surface and gain mechanical grip.
But ideal pressures can vary greatly ... on the Hoosier S05s, some heavy cars were running as much as 55 - 60 psi.
However, on the awesome Kumho 710s, ideal pressures were closer to 25 psi.
But ideal pressures can vary greatly ... on the Hoosier S05s, some heavy cars were running as much as 55 - 60 psi.
However, on the awesome Kumho 710s, ideal pressures were closer to 25 psi.
My Yokohama Slick tires run around 25 psi (depending on track and weather conditions). Weather and track temperature is also a factor to take in consideration. The lower the outside temp the lower you set the tire pressure. If you go to low with high outside temps, the air temp and pressure in the tire will go sky high because of the friction of air molecules (the air and tire moves more). If the outside temp is low, you want this to happen, because you want temp in your tires (thus resulting in more working pressure). Important is, that the temps on the inside, outside and mid section of the tire is as close as possible. If so, you have the right tire pressure.
