Tire size calculator

For 265/70R17 → 285/70R17, nominal diameter grows from 31.6 to 32.7 in (803 to 831 mm). Section width grows from 10.4 to 11.2 in, while sidewall height grows from 7.3 to 7.9 in. Use callouts A–D and the scaled side and front views to distinguish these dimensions.

Nominal revolutions per mile fall from 638 to 617. The speedometer line reads 62.1 mph true at 60 mph indicated, assuming the original size was the calibration basis. The +3.5% diameter change falls outside the ±3% line: a tire-shop rule of thumb, not a law or vehicle maker specification.

The neighbor table applies that diameter window and includes purchase links; it does not establish fit. Use the popular size index to browse sizes, then compare their dimensions.

Sidewall height equals section width multiplied by the aspect ratio divided by one hundred. Overall diameter equals the rim diameter converted to millimeters, plus twice the sidewall height. Revolutions per mile equal inches per mile divided by tire circumference.

These are unloaded, nominal dimensions. The published-measurement table draws from Nitto, Firestone, Kumho, Toyo and Mickey Thompson, whose 285/70R17 diameters range from 32.76 to 33.15 in, versus 32.71 in by the formula.

The maker tables were checked on October 15, 2026. Use their model-specific measurements alongside the nominal comparison; the sidewall anatomy and tire size reading guide explain the size marking.

The size marking alone does not identify load range, weight or tread depth. Across the Nitto, Firestone, Kumho, Toyo and Mickey Thompson tables, 285/70R17 listings include LT and passenger versions, with load ranges SL and E. Published weights span 42.1 to 66.9 lbs, and new tread depths span 12/32 to 20/32 in.

Nitto lists its LT285/70R17 Ridge Grappler at 57.9 lbs with 16.4/32 in tread depth. Toyo lists its LT285/70R17 Open Country R/T Trail at 57 lbs with 16.5/32 in tread depth. Both list load range E, but their service descriptions differ.

For load and inflation pressure, see the tire and loading placard on the driver's door jamb. Under 49 CFR 571.110 (FMVSS No. 110), that placard identifies the original tire size; the calculator does not replace it.

A larger nominal diameter travels farther per revolution, changing speedometer and odometer readings. In this example, 100 km/h indicated becomes 103.5 km/h true; the odometer records less distance than traveled. The speedometer table shows the calculated change at other indicated speeds.

By the formula, engine speed at 65 mph with a 3.73 axle ratio and 1.00 transmission gear falls from 2,578 to 2,492 rpm. Multiplying the original axle ratio by the new-to-old diameter ratio gives 3.86 to restore the original engine speed; this is calculation only.

Nominal ground clearance at the axle increases by half the diameter change: 0.55 in (14 mm). The taller, wider tire also changes clearance around the wheel. Fit depends on the vehicle, wheels and suspension.