2018 GMC Sierra — 1500 4wd Regualar Cab

The 2018 GMC Sierra 1500 4wd Regualar Cab shipped with 5 different factory tire sizes, depending on the wheel package it left the factory with (this can also reflect a staggered front/rear setup). Check your tire sidewall or door placard to confirm which one applies to your vehicle.

This trim shipped with more than one tire size (staggered fitment, front/rear, or optional wheel package). Confirm which one matches your vehicle by checking your tire sidewall or door placard.

255/70R17

Section width255 mm
Aspect ratio (sidewall height)70% (178.5 mm)
Rim diameter17"
Overall tire diameter~31.1"
Revolutions per mile~649

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265/70R17

Section width265 mm
Aspect ratio (sidewall height)70% (185.5 mm)
Rim diameter17"
Overall tire diameter~31.6"
Revolutions per mile~638

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265/65R18

Section width265 mm
Aspect ratio (sidewall height)65% (172.3 mm)
Rim diameter18"
Overall tire diameter~31.6"
Revolutions per mile~639

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275/55R20

Section width275 mm
Aspect ratio (sidewall height)55% (151.3 mm)
Rim diameter20"
Overall tire diameter~31.9"
Revolutions per mile~632

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285/45R22

Section width285 mm
Aspect ratio (sidewall height)45% (128.3 mm)
Rim diameter22"
Overall tire diameter~32.1"
Revolutions per mile~628

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What this size means for your GMC Sierra

On the 2018 GMC Sierra 1500 4wd Regualar Cab, the factory 255/70R17 measures about 31.1″ in overall diameter with a 178.5 mm (7″) sidewall, and completes roughly 649 revolutions per mile. Its 70-series aspect ratio gives a tall sidewall of the kind used on trucks, SUVs, and older passenger cars, built for cushioning and load. In tire terms it is a passenger (P-metric / Euro-metric) size.

The 255/70R17 and 265/70R17 differ in both width and overall diameter (0.5″, 1.6%), which usually means a staggered front/rear setup — the two sizes are not interchangeable side to side, so match each to its correct axle.

Other 2018 GMC Sierra trims

GMC Sierra tire sizes by year

See every GMC Sierra year & trim →

How to read a tire size

A tire size like 225/45R17 breaks down into three parts: the first number is the section width in millimeters (the tire's width from sidewall to sidewall), the second is the aspect ratio — the sidewall's height as a percentage of that width — and the number after the "R" is the rim diameter in inches. A letter prefix (P or LT) indicates Passenger or Light Truck construction; its absence usually means Euro-metric sizing.

Some trucks and off-road tires instead use "flotation" sizing, like 37X12.50R17 — here the numbers are the tire's overall diameter and width in inches directly, with the rim diameter last.

Always verify against the tire information placard on your driver's-side door jamb or your owner's manual before purchasing — tire size can vary by factory option package even within the same trim.