1996 GMC Savana Van Owner's Manual - Page 270

A CAUTION: Mixing tires could cause you to lose control while driving. If you mix tires of different sizesor types (radial and bias-belted tires), the vehicle may not handle properly, andyou could have a crash. Using tires of different sizes may also cause damage to yourvehicle. Be sure to use the same size and type tires all wheels. on Uniform Tire Quality Grading The following information relates to the system developed by the United States National Highway Traffic Safety Administration, which grades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.) The grades are molded on the sidewalls of most passenger car tires. The Uniform Tire Quality Grading system does not apply to deep tread, winter-type snow tires, space-saver or temporary use spare tires, tires with nominal rim diameters of 10 t o 12 inches (25 to 30 cm), or to some limited-production tires. While the tires available on General Motors passenger cars and light trucks may vary with respect to these grades, they must also conform to Federal safety requirements and additional General Motors Tire Performance Criteria (TYC) standards. 6-46