GMC Sierra 2500HD tire size by year

The 2011–2026 GMC Sierra 2500HD was sold from the factory on 265/70R18, 265/60R20, on 18x8, 20x8.5 wheels. Which one your truck has depends on its trim and wheel package, so check the placard inside the driver's door jamb — that sticker lists the sizes your specific truck left the factory on, together with the correct cold inflation pressures.

About 32.6 inches overall. The sidewall is 7.3 inches tall (70 per cent figures are of the section width, not the wheel), the section width is 10.4 inches, and it turns roughly 619 revolutions per mile. Those are the numbers to compare against when you are sizing up.

Across 2001–2026 the largest factory size on record is 265/70R18 at about 32.6 inches tall, and the smallest is 245/75R16 at about 30.5 inches. If your truck came on the smaller size, the larger one is a known-good fitment for the same platform — which makes it the safest first upsize, though offset and trim still differ.

Usually one size, around 3 per cent more overall diameter, fits on stock suspension. Past that you are into trimming the front valance or fitting a levelling kit, and the limiting factor is often the wheel offset rather than the tire height — a wider tire on a lower offset hits the fender liner at full lock long before diameter becomes the issue. Work out the exact clearance before you buy.

Yes, proportionally. A tire 3 per cent taller than stock makes the speedometer read about 3 per cent low, so an indicated 70 is really 72, and the odometer under-counts by the same amount. It also shifts the effective gear ratio, which on a truck that tows is felt as softer acceleration and more downshifting on grades.

Wheel fitment starts with the bolt pattern, then hub bore, then offset. All three for every Sierra 2500HD generation are on the bolt pattern page for this truck, along with the stud thread and lug torque. The factory wheel sizes on this page tell you what widths and diameters the truck was engineered around.