Guide

AWD and mismatched tire sizes

On many all-wheel-drive vehicles, tires of different diameters on the front and rear axles turn at different speeds, which the drivetrain has to absorb. That's why AWD owner's manuals often require all four tires to match in size and be close in tread depth. The limit is set by your vehicle maker; check the owner's manual.

Compare circumference

The % difference in diameter shown by the calculator is also the % difference in circumference and revolutions per mile. For worn vs new tires the difference comes from tread depth rather than size; your manual or tire shop can tell you the allowed difference.

1

Your current size

e.g. 265/70R17, 2657017 or 33x12.50R20

Where do I find my size?

It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.

2

Size you're considering

 

More guides

How to read a tire size · Nominal vs actual diameter · The 3% rule · Load index & speed rating · Revs per mile chart · Tire size chart

Important: These are calculated (nominal) dimensions, not a fitment recommendation. Real tires of the same size differ by brand and model (makers allow about ±3% of section height), and width changes with the rim it is mounted on. The math can't see wheel width and offset, clearance at full steering lock and suspension travel, load index, speed rating, or what your vehicle maker approves. Before changing size, check your door-jamb placard and owner's manual and ask a tire professional. A replacement tire must meet or exceed the load index and speed rating on the placard.