Replacement Tires

GENERAL INFORMATION
A Tire Performance Criteria (TPC) specifications number is molded in the sidewall near the size of all original equipment tires. This number assures that the tire meets performance standards for traction endurance, dimensions, noise, handling, rolling resistance, etc. Usually, a specific TPC number is assigned to each tire size.

Replacement tires should be of the same size, load range, speed rating and construction as the original tires. This means that replacement tires should have the same TPC specification number. Tires of any other size or construction may seriously affect ride handling, speedometer/odometer calibration, vehicle ground clearance and tire clearance to the body and chassis. (This does not apply to the factory-furnished spare.) Although the tread might differ, tires of different manufacturers that have the same TPC specification numbers may be intermixed on the same vehicle.

New tires should be installed in pairs on the same axle. If only a single new tire is to be installed it should be paired with the tire having the most tread to equalize braking traction.

PASSENGER TIRE SERVICE DESCRIPTION
Most tires today have a service description branded on the sidewall after the tire size. This service description consists of two parts: The load index and the speed symbol. The load index is a number usually between 75 and 115, which defines the tire's load capacity at maximum inflation. Higher numbers mean greater load capacity.

The speed symbol is a letter usually between P and 7, which defines the speed capability of the tire. In the past, this letter might have been part of the tire size; this continues to be the case with some V rated and Z rated tires. The higher the letter, the greater the speed capability.

Tire companies have charts which define equivalent loads and speeds for all load indexes and speed symbols that make up the tire service description.