2003 GMC Yukon Owner's Manual - Page 422

Buying New Tires To find out what kind and size of tires you need, look at the Certification/Tire label. The tires installed on your vehicle when it was new had a Tire Performance Criteria Specifications (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). 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. {CAUTION: 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. If your vehicle has 17 inch road tires (those originally installed on your vehicle) it is all right to drive with the 16 inch spare tire that came with your vehicle. When new, your vehicle included a spare tire and wheel assembly with the same overall diameter as your vehicle's road tires and wheels. Because this spare tire was developed for use on your vehicle, it will not affect vehicle handling or cause damage to your vehicle. 5-64