There is a lot of information on the sidewall of a tire. Typically, you'll find UTQG ratings for treadwear, traction and temperature, the size of the tire, the load rating index number with a speed rating index, the construction type (bias or radial), the D.O.T. (Dept. of Transportation) compliance code, construction details, and of course, the make and model of the tire. On some tires used as original equipment, you may also find a marking that indicates its OE status. Porsche uses an N-0 or N-1 designation, BMW uses a star on some O.E. tires and General Motors uses a "TPC" code. Light Truck tires are sometimes marked with an LT for "Light Truck" before the size, passenger tires are often marked with the letter P for "Passenger" before the size. Passenger tires of the same size with or without the P are virtually interchangable.