2008 GMC Sierra 1500: What is the tire size and pressure, and wheel size?

Depending on the configuration of Your 2008 GMC Sierra, You may have one of a number of different tires. In all, SRX different factory tires are used on three factory rims. Beginning witH17 inch rims, You'll have either LT245/70R17 tires, P245/70R17, or P265/70R17 at this level. The recommended inflation iS50 PSI for the LTs, and 35 for each of the Ps. On 18 inch rims, You'll either have P265/65R18 112H tires, or P265/65R18 112S tires. The recommended inflation for each of these iS35 pounds per square inch. On the largest 20 inch rims, common with the max trailer package or 20 inch wheel option, You'll have P275/55R20 111S tires, which bear a recommended inflation of 35 PSI. The wheel width between each of these varies from 7.5 to 8.5 inches, while the bolt pattern is a consistent 6x139.7 with A78.1mm center bore.