275/30R20 vs 245/35R20

245/35R20 is 0.26 in (6.5 mm) taller than 275/30R20, a +0.97% diameter difference. With the speedometer set for 275/30R20, an indicated 60 mph is 60.6 mph on 245/35R20.

Is this a safe swap?

Diameter difference +0.97%: under 1%

By overall diameter alone, 245/35R20 is a near match for 275/30R20; 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.

275/30R20 vs 245/35R20 differences
Measurement	275/30R20	245/35R20	Difference	% diff
Overall diameter	26.50 in (673.0 mm)	26.75 in (679.5 mm)	+0.26 in (+6.5 mm)	+0.97%
Sidewall height	3.25 in (82.5 mm)	3.38 in (85.8 mm)	+0.13 in (+3.3 mm)	+3.94%
Section width	10.83 in (275.0 mm)	9.65 in (245.0 mm)	−1.18 in (−30.0 mm)	−10.91%
Circumference	83.24 in (2,114.3 mm)	84.04 in (2,134.7 mm)	+0.80 in (+20.4 mm)	+0.97%
Revolutions per mile	761	754	−7	−0.96%

True speed with the speedometer calibrated for 275/30R20
Indicated	Actual on 275/30R20	Actual on 245/35R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.7 mph	+0.7 mph

Ride-height change: 245/35R20 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

245/35R20 is 0.26 in taller than 275/30R20 and 30 mm narrower, a 0.97% difference in overall diameter.

With the speedometer calibrated for 275/30R20, an indicated 60 mph is actually 60.6 mph on 245/35R20, and revolutions per mile change from 761 to 754.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 275/30R20

Other comparisons with 245/35R20

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