245/45R20 vs 315/35R20

315/35R20 is 0.00 in (0.0 mm) taller than 245/45R20, a 0.00% diameter difference. With the speedometer set for 245/45R20, an indicated 60 mph is 60.0 mph on 315/35R20.

Is this a safe swap?

Diameter difference 0.00%: under 1%

By overall diameter alone, 315/35R20 is a near match for 245/45R20; 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.

245/45R20 vs 315/35R20 differences
Measurement	245/45R20	315/35R20	Difference	% diff
Overall diameter	28.68 in (728.5 mm)	28.68 in (728.5 mm)	0.00 in (0.0 mm)	0.00%
Sidewall height	4.34 in (110.3 mm)	4.34 in (110.3 mm)	0.00 in (0.0 mm)	0.00%
Section width	9.65 in (245.0 mm)	12.40 in (315.0 mm)	+2.76 in (+70.0 mm)	+28.57%
Circumference	90.10 in (2,288.7 mm)	90.10 in (2,288.7 mm)	0.00 in (0.0 mm)	0.00%
Revolutions per mile	703	703	0	0.00%

True speed with the speedometer calibrated for 245/45R20
Indicated	Actual on 245/45R20	Actual on 315/35R20
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 315/35R20 does not change the vehicle at the axle (half the 0.0 mm diameter difference).

315/35R20 is the same height as 245/45R20 and 70 mm wider, a 0.00% difference in overall diameter.

With the speedometer calibrated for 245/45R20, an indicated 60 mph is actually 60.0 mph on 315/35R20, and revolutions per mile change from 703 to 703.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 245/45R20

Other comparisons with 315/35R20

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