1994 GMC Jimmy Owner's Manual - Page 282

If you ever replace your tires with those not having a Spec number, TPC make sure they are the same size, load range, speed rating and construction type (bias, bias-belted or radial) as your original tires. Uniform Tire Quality Grading The following information relates to the system developed the United by 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.) Treadwear The treadwear grade is acomparative rating based on the wear rate the of tire when tested under controlled conditions a specified government test on course. For example, a tire graded150 would wear one and a half (1 1/2) times as well on the governmentcourse as a tire graded 100. The relative performance of tires depends upon the actual conditionstheir use, of however, andmay depart significantlyfrom the norm due to variations in driving habits, service practices and differences in road characteristics and climate. Traction - A, 6, C The traction grades, from highest to lowest are: A, B, and C . They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfacesasphalt and concrete. of A tire markedC may have poor traction perforinance. Warning: The traction grade assigned to this tire is based braking on (straight-ahead) traction tests and does not include cornering (turning) traction. 6-46