Autocross Tire Pressures (basic Q's)

[67rally]

I posted this over on Lateral-G but haven't gotten a response yet...

I just signed up for my first AutoX in my with my '67 Camaro. I was looking for some decent baseline tire pressure recommendations to start the day out with, but didn't get much help from the manufacturer. I don't have a set of dedicated track tires/wheels yet, so I'm going into it with my Nitto 555's. 245/40/18 up front and 275/40/18 in the rear.

Is there a general rule of thumb (i.e. 5 more psi than on the street, or increase one/not the other, or start at xxx psi and work your way up or down based on wear patterns) that would be a good starting point? Thanks.

[OG_Racing]

On my car i run the RS3's. i start with 28 cold and after a run it should climb up to 32psi, they seem to grip the best around 32psi hot. When i ran rivals, i would start it at 32 and they liked to be around the 38psi hot. every tire is going to be a little different. i would call nitto and find out what the engineers say to run them at, and keep in mind the hot and cold pressures.

[67rally]

On my car i run the RS3's. i start with 28 cold and after a run it should climb up to 32psi, they seem to grip the best around 32psi hot. When i ran rivals, i would start it at 32 and they liked to be around the 38psi hot. every tire is going to be a little different. i would call nitto and find out what the engineers say to run them at, and keep in mind the hot and cold pressures.

Thanks, I contacted Nitto before posting this, gave them my car specs, and asked what they recommended for daily driving vs autox and this was their reply:

Regarding your inquiry, based on the vehicle information you provided, the recommended replacement psi for the NT555 245/40ZR18 93W and NT555 275/40ZR18 103W is 32 psi for front and 29 psi rear tires.

So I asked: "Thank you. So you don't recommend changing/increasing the tire pressure for an Autocross vs daily driving?"

The NT555 has excellent traction response and handling capabilities with great performance, however, it is not considered a dedicated competition tire. The optimum tire pressures for track use would depend on how much your tire pressures grow on a specific track. If using NT555 for track use, the right setup and PSI would ultimately depend on what you feel most comfortable with.

Nitto Tire U.S.A Inc. cannot endorse using a lower PSI than what is recommended for daily use.

[OG_Racing]

Start them out on 32-29 psi and watch the triangles. all tires have 3 triangles on them. use a pice of chalk, sharpie, paint, anything that you can see. mark the triangle. the road will wipe away the chalk and show you where the tire is contacting the road. you want the road to touch the very tip of the triangle, if that happens you have the correct air pressure. if the road has wiped the chalk off the triangle you have too little air- add more. If the road hasn't touched the triangle then you have too much air- take some out.

At first it will be hard to tell how much to add or subtract, but after a while you'll get a feel for your car.

hope this helps

tire triangles.

[67rally]

Start them out on 32-29 psi and watch the triangles. all tires have 3 triangles on them. use a pice of chalk, sharpie, paint, anything that you can see. mark the triangle. the road will wipe away the chalk and show you where the tire is contacting the road. you want the road to touch the very tip of the triangle, if that happens you have the correct air pressure. if the road has wiped the chalk off the triangle you have too little air- add more. If the road hasn't touched the triangle then you have too much air- take some out.

At first it will be hard to tell how much to add or subtract, but after a while you'll get a feel for your car.

hope this helps

That's cool, I never knew those were there. Thanks.

[Tomswheels]

The truth of the matter is the Nittos dont have nearly the sidewall stiffness of the RS3, and therefore will require more PSI to stop them from rolling over. You may find they work better at 36-40 PSI...

[struck by Lightning]

The truth of the matter is the Nittos dont have nearly the sidewall stiffness of the RS3, and therefore will require more PSI to stop them from rolling over. You may find they work better at 36-40 PSI...

Tom is right about the Nitto's as I have found 36 PSI works best however my truck is 4,700 pounds.