1997 Pontiac Firebird Owner's Manual - Page 300

Traction -- A, B, C The traction grades, from highest to lowest, are A, B, and C, and they represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government testsurfaces of asphalt and concrete. A tire marked C may have poor traction performance. Warning: The traction grade assigned to this tire is based on braking (straightahead) traction tests and does not include cornering (turning) traction. Federal Motor Vehicle Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. Warning: The temperature grade for tire is this established for a tire that is properly inflated and not overloaded. Excessive speed, underinflation, o r excessive loading,either separately or in combination, can cause heat buildup and possible tire failure. Wheel Alignmentand Tire Balance The wheels on your vehicle were aligned and balanced carefully at the factory to give you the longest tire life and best overall performance. Scheduled wheel alignment and wheel balancing are not needed. However, if you notice unusual tire wear or your vehicle pulling one way or theother, the alignment may need to bereset. If you notice your vehicle vibrating when driving on a smooth road,your wheels may need to be rebalanced. Temperature -- A, B, C The temperature grades are A (the highest), B, and C , representing the tire's resistance tothe generation of heat and its ability to dissipate heat when tested under controlled conditions ona specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger cartires must meet under the