315/60R20 vs 35x12.50R20

35x12.50R20 is 0.12 in (3.0 mm) taller than 315/60R20, a +0.34% diameter difference. With the speedometer set for 315/60R20, an indicated 60 mph is 60.2 mph on 35x12.50R20.

Is this a safe swap?

Diameter difference +0.34%: under 1%

By overall diameter alone, 35x12.50R20 is a near match for 315/60R20; 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.

315/60R20 vs 35x12.50R20 differences
Measurement	315/60R20	35x12.50R20	Difference	% diff
Overall diameter	34.88 in (886.0 mm)	35.00 in (889.0 mm)	+0.12 in (+3.0 mm)	+0.34%
Sidewall height	7.44 in (189.0 mm)	7.50 in (190.5 mm)	+0.06 in (+1.5 mm)	+0.79%
Section width	12.40 in (315.0 mm)	12.50 in (317.5 mm)	+0.10 in (+2.5 mm)	+0.79%
Circumference	109.58 in (2,783.5 mm)	109.96 in (2,792.9 mm)	+0.37 in (+9.4 mm)	+0.34%
Revolutions per mile	578	576	−2	−0.34%

True speed with the speedometer calibrated for 315/60R20
Indicated	Actual on 315/60R20	Actual on 35x12.50R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.3 mph	+0.3 mph

Ride-height change: 35x12.50R20 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +3.0 mm diameter difference).

35x12.50R20 is 0.12 in taller than 315/60R20 and 3 mm wider, a 0.34% difference in overall diameter.

With the speedometer calibrated for 315/60R20, an indicated 60 mph is actually 60.2 mph on 35x12.50R20, and revolutions per mile change from 578 to 576.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 315/60R20

Other comparisons with 35x12.50R20

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