Was using 275-35-17s, went to the 255-50-16s worked better. Now using the et streets. Running 8.5 psi before burnout. The reason why the cars move around with the et streets, is because the et streets are a bias tire, and running radials in the front. Also i noticed with my 5 speed as the car came up on boost thats win the car would drift in the rear, not the same with the automatic. Tire pressure depends on the car setup. I run 8.5 psi and cut high 1.50s while eric( z324u) runs more pressure and cuts high1.40s all the time.