265/40R21 vs 315/30R22

315/30R22 is 0.09 in (2.4 mm) taller than 265/40R21, a +0.32% diameter difference. With the speedometer set for 265/40R21, an indicated 60 mph is 60.2 mph on 315/30R22.

Is this a safe swap?

Diameter difference +0.32%: under 1%

By overall diameter alone, 315/30R22 is a near match for 265/40R21; 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.

265/40R21 vs 315/30R22 differences
Measurement	265/40R21	315/30R22	Difference	% diff
Overall diameter	29.35 in (745.4 mm)	29.44 in (747.8 mm)	+0.09 in (+2.4 mm)	+0.32%
Sidewall height	4.17 in (106.0 mm)	3.72 in (94.5 mm)	−0.45 in (−11.5 mm)	−10.85%
Section width	10.43 in (265.0 mm)	12.40 in (315.0 mm)	+1.97 in (+50.0 mm)	+18.87%
Circumference	92.19 in (2,341.7 mm)	92.49 in (2,349.3 mm)	+0.30 in (+7.5 mm)	+0.32%
Revolutions per mile	687	685	−2	−0.32%

True speed with the speedometer calibrated for 265/40R21
Indicated	Actual on 265/40R21	Actual on 315/30R22	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	75.2 mph	+0.2 mph

Ride-height change: 315/30R22 raises the vehicle by 0.05 in (1.2 mm) at the axle (half the +2.4 mm diameter difference).

315/30R22 is 0.09 in taller than 265/40R21 and 50 mm wider, a 0.32% difference in overall diameter.

With the speedometer calibrated for 265/40R21, an indicated 60 mph is actually 60.2 mph on 315/30R22, and revolutions per mile change from 687 to 685.

315/30R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 265/40R21.

Size pages

Other comparisons with 265/40R21

Other comparisons with 315/30R22

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