Tires - Speed Rated Information
Group Ref.: 3 - Steering/SuspensionBulletin No.: 433502
Date: July, 1994
INFORMATION
SUBJECT:
SPEED RATED TIRES
MODELS:
1995 AND PRIOR YEAR PASSENGER CARS AND LIGHT DUTY TRUCKS
All original equipment passenger car and light duty truck tires used by General Motors have a speed rating symbol molded on their sidewall. This speed symbol, along with the tire's load index, make up the service description that follows the tire's size. The original equipment tire size, speed rating, and recommended inflation pressure are listed on the tire placard usually located on the driver's door edge. WHEN REPLACING TIRES, NEVER INSTALL A TIRE THAT IS A SMALLER SIZE OR LESSER SPEED RATING THAN THAT USED AS ORIGINAL EQUIPMENT. As in the past, it is recommended that replacement tires have a TPC (Tire Performance Criteria) number on the sidewall that is identical to that on the original tires.
Common speed rating on tires used by General Motors are as follows: (see illustration)
IMPORTANT:
Most base all season tires and touring tires used by GM are S rated. Performance tires will usually have a higher speed rating. High performance tires are usually Z rated. Z rated tires carry the Z symbol within the tire size, rather than after the size in the service description. These speeds apply only at the tire's full pressure. An underinflated tire will not meet its speed rating capability.