what is going to be the tire pressure for 255/40/17??? is it the same as stock 235/45/17.

 

totally depends on the tire and what you're doing with them.

what type tires are they?

 

40psi always works or atleast thats what they tell me down here in miami

 

dunlop Z1 star spec for dd and track

 

I run around 3 psi over stock with 255, more on the track obviously.

 

thanks

 

Check the side of the tire, should have psi recommendation. They arent stock tires, so no longer use stock pressures. Each tire is different like was said above, you cant just go on what you "use to use" on your old tires.

I would start with the recommendation on the side cold. Then take them for a few laps on a track or autoX, warm them up, check the pressure. Lower it down from there to increase grip. If you go to far they may start losing traction, thats when you bump them back up a couple psi and have your setting. make sure this is all done while air temp in the tires is HOT. As in, right after a hard lap.