RUBBER MATCH For one reason or another, many vehicles end up riding on mismatched tires. Handling can be affected as a result. Even if the sizes printed on the sidewalls all match, there are small (but significant) differences in outside diameter from one manufacturer to the next. On some low-profile tires, a difference of four pounds per square inch (psi) from one side to the other is enough to create a size difference that affects handling. Even if the tires on one axle are both the same size but different from the other axle, there can still be some effect on the steering. This potential problem points out the wisdom of replacing all four tires at once as they show signs of wear. HINT: Driving enthusiasts can change the understeer/oversteer characteristics of their vehicles simply by making the right changes in tire inflation.