2003 Pontiac Montana Owner's Manual - Page 384

Buying New Tires To find out what kind and size of tires you need, look at the Certificationflire label. The tires installed on your vehicle when it was new had a Tire Performance Criteria Specification (TPC Spec) number on each tire's sidewall. When you get new tires, get ones with that same TPC Spec number. That way your vehicle will continue to have tires that are designed to give proper endurance, handling, speed rating, traction, ride and other things during normal service on your vehicle. If your tires have an all-season tread design, the TPC number will be followed by an "MS" (for mud and snow). Mixing tires could cause you to lose control while driving. If you mix tires of different sizes or types (radial and bias-belted tires), the vehicle may not handle properly, and you could have a crash. Using tires of different sizes may also cause damage to your vehicle. Be sure to use the same size and type tires on all wheels. It's all right to drive with your compact spare temporarily, it was developed for use on your vehicle.See "Compact Spare Tire" in the index. If you ever replace your tires with those not having a TPC Spec number, make sure they are the same size, load range, speed rating and construction type (bias, bias-belted or radial) as your original tires. you use bias-ply tires on your v icle, the wheel rim flanges could develop cracks after many miles of driving.A tire andlor wheel could fail suddenly, causing a crash. Use only radial-ply tires with the wheels your vehicle. on I __ 5-63