285/30R20 vs 245/35R20

245/35R20 is 0.02 in (0.5 mm) taller than 285/30R20, a +0.07% diameter difference. With the speedometer set for 285/30R20, an indicated 60 mph is 60.0 mph on 245/35R20.

Is this a safe swap?

Diameter difference +0.07%: under 1%

By overall diameter alone, 245/35R20 is a near match for 285/30R20; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

285/30R20 vs 245/35R20 differences
Measurement	285/30R20	245/35R20	Difference	% diff
Overall diameter	26.73 in (679.0 mm)	26.75 in (679.5 mm)	+0.02 in (+0.5 mm)	+0.07%
Sidewall height	3.37 in (85.5 mm)	3.38 in (85.8 mm)	+0.01 in (+0.3 mm)	+0.29%
Section width	11.22 in (285.0 mm)	9.65 in (245.0 mm)	−1.57 in (−40.0 mm)	−14.04%
Circumference	83.98 in (2,133.1 mm)	84.04 in (2,134.7 mm)	+0.06 in (+1.6 mm)	+0.07%
Revolutions per mile	754	754	−1	−0.07%

True speed with the speedometer calibrated for 285/30R20
Indicated	Actual on 285/30R20	Actual on 245/35R20	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	60.0 mph	0.0 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 245/35R20 raises the vehicle by 0.01 in (0.3 mm) at the axle (half the +0.5 mm diameter difference).

245/35R20 is 0.02 in taller than 285/30R20 and 40 mm narrower, a 0.07% difference in overall diameter.

With the speedometer calibrated for 285/30R20, an indicated 60 mph is actually 60.0 mph on 245/35R20, and revolutions per mile change from 754 to 754.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 285/30R20

Other comparisons with 245/35R20

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.