Replacement Tires

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

WARNING: Do not mix different types of tires on the same vehicle such as radial, bias and bias-belted tires except in an emergency, because vehicle handling may be seriously affected and may result in loss of control.

Replacement tires should be of the same size, load range and construction as those originally on the vehicle. This can best be accomplished by using tires of the same TPC specification number. Use of any other tire size or construction type 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 spare furnished with the vehicle.

It is recommended that new tires be installed in pairs on the same axle. In order to equalize braking traction, if it is necessary to replace only one tire, the replacement should be paired with the tire that has the most tread.

Although they may appear different in tread design, tires built by different manufacturers with identical TPC specification numbers can be intermixed on the same vehicle.

Tires should be replaced when:
1. They are worn to a point where 1.6 mm (0.063 inch) or less tread remains, or the cord or fabric is showing. To help detect this condition, tires have built-in tread wear indicators that appear between the tread grooves when the tread is worn to 1.6 mm (0.063 inch) or less; When the indicators appear in two or more adjacent grooves at three spots around the tire, the tire should be replaced.
2. The tread or sidewall is cracked, cut or snagged deeply enough to expose the cord or fabric.
3. The tire has a bump, bulge or split. Slight sidewall indentations are normal and should not affect ride.
4. The tire has a puncture, cut or other damage that cannot be correctly repaired because of the size or location of the damage.

PASSENGER TIRE SERVICE DESCRIPTION
Most tires today have a service description branded on the side wall after the tire size. This service description consist of two parts: The load index and the speed symbol. The load index is a number usually between 75 and 115, which defines the tires load capacity at maximum inflation. Higher numbers mean greater load capacity. The speed symbol is a letter usually between P and Z which defines the speed capability of the tire. In the past, this letter may have been part of the tire size; this continues to be the case with some V and Z rated tires. The higher the letter, the greater the speed capability. The tire companies have charts which define equivalent loads and speeds for all load indexes and speed symbols that make up the tire service description.

NOTE: When replacing tires, never install a tire that is a smaller size or lesser speed rating than that used as original equipment. These speeds only apply at the tire's full pressure. An under-inflated tire will not meet its speed rating capability.

The chart below shows the common speed rating on tires:

Speed Symbol Maximum Speed (km/h) Maximum Speed (mph)
S 160 112
T 190 118
U 200 124
H 210 130
V 240 149
Z Over 240 Over 149