Tire inflation pressures can have significant impact on competitive driving, affecting performance and handling capabilities. Basic goal is to maximize the grip of the tires by having the tire contact patch as big as possible, then making adjustments to suit the racing track and your driving style.
For front engine cars with front wheel drive or all-wheel drive, front tires should be inflated to 40 to 45 psi, while rear tire pressure should be in the 30 to 40 psi range. For rear wheel drive, front tire inflation pressures should be around 35 - 45 psi, with rear tires inflated to 30 - 40 psi. If your car has mid or rear engine, inflate your front tires to 35 - 45 psi, and rear tires should have tire inflation pressures of 35 to 40 psi.
To decrease understeer, increate front tire pressures and decrease rear tire pressures. For decreased oversteer, reduce front tire pressures and inflate rear tires higher.
When racing on when track, inflate your tires 5 to 8 psi above what tire pressures you would normally use in dry conditions. This will round the profile of the tires and reduce hydroplaning.
It is best to use nitrogen instead of outside air in your competition tires as nitrogen is a dry gas and effects of air moisture are eliminated. With nitrogen the increase in tire pressure due to temperature generated by heat during extreme racing is more linear and predictable. Nitrogen-filled tires run cooler, providing better grip when racing.
Remember to reset your tires to normal inflation pressures when you are going back to street driving.