TireSizesFinder

245/45R21 vs 315/35R21

315/35R21 is 0.00 in (0.0 mm) taller than 245/45R21, a 0.00% diameter difference. With the speedometer set for 245/45R21, an indicated 60 mph is 60.0 mph on 315/35R21.

Is this a safe swap?

Diameter difference 0.00%: under 1%

By overall diameter alone, 315/35R21 is a near match for 245/45R21; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 245/45R21 (29.68 in) vs 315/35R21 (29.68 in)245/45R2129.68 in × 9.65 in315/35R2129.68 in × 12.40 in
Side profile and tread width, drawn to the same scale.
245/45R21 vs 315/35R21 differences
Measurement245/45R21315/35R21Difference% diff
Overall diameter29.68 in (753.9 mm)29.68 in (753.9 mm)0.00 in (0.0 mm)0.00%
Sidewall height4.34 in (110.3 mm)4.34 in (110.3 mm)0.00 in (0.0 mm)0.00%
Section width9.65 in (245.0 mm)12.40 in (315.0 mm)+2.76 in (+70.0 mm)+28.57%
Circumference93.25 in (2,368.4 mm)93.25 in (2,368.4 mm)0.00 in (0.0 mm)0.00%
Revolutions per mile67967900.00%
True speed with the speedometer calibrated for 245/45R21
IndicatedActual on 245/45R21Actual on 315/35R21Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.0 mph0.0 mph
75 mph75.0 mph75.0 mph0.0 mph

Ride-height change: 315/35R21 does not change the vehicle at the axle (half the 0.0 mm diameter difference).

315/35R21 is the same height as 245/45R21 and 70 mm wider, a 0.00% difference in overall diameter.

With the speedometer calibrated for 245/45R21, an indicated 60 mph is actually 60.0 mph on 315/35R21, and revolutions per mile change from 679 to 679.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 245/45R21

Other comparisons with 315/35R21

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.