help with autocross tire pressures on 18's
 

Hi all, reading up on tips on autocrossing threads as I'm getting ready to do my first event next weekend. I know a lot of people are autocrossing on the 19 rays and Nismo wheels but I haven't really seen much talk about on 18's. Knowing that most people are running 38psi up front and 35 in the rear on the 19's, brings me to the though of should i be running more in front and rear since I have more sidewall? Current set up is 255/45/18 up front and 275/40/18 in the rears on Bridgestone RE760's. Not the greatest tire but thats besides the point right now. Just hoping to get some input on people AutoXing on 18's and the pressures and tires sizes they are running. Thanks in advance!

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.

thank you for you very in depth response. i know all the tires will be run different pressures and react differently but i was just wanting to see what others run and if it is higher then say the autoxers on 19's. i feel like im probably have to run atleast 40 in front as i know i get quite a bit of tire roll already just with aggressive daily driving. im not looking for an exact number. just wondering what everyone else is on.

As the last guy replied, just mark your tires with a grease pen or chalk and try to get as much roll over on the tread as you can without going off of the tread. In my S14 this is normally high 20s.