help with autocross tire pressures on 18's

DR_

There are too many variable to give you a definite answer as air pressures are just one aspect of the setup. If the sidewalls on your RE760 are soft they might require more pressure. Typically what people do at autocrosses on new type of tires on their car is look at how much the tires are rolling over onto the sidewall. There should be little arrows on the sidewall and the roll over should not go beyond that. You can use a tire marker and paint on the tire from the sidewall onto the tread for more observation points. I think a safe place to start is 35f/35r and then adjust accordingly.

If you want to get more technical you get a tire temp probe and adjust accordingly to what your temps are. Then long term you look at the tire wear over the life of your tire and adjust accordingly. A lot of times your temps will say one thing while your tire wear will say another and then you make a compromise if you want better tire life.