295/40R21 vs 305/35R22

305/35R22 is 0.11 in (2.9 mm) taller than 295/40R21, a +0.38% diameter difference. With the speedometer set for 295/40R21, an indicated 60 mph is 60.2 mph on 305/35R22.

Is this a safe swap?

Diameter difference +0.38%: under 1%

By overall diameter alone, 305/35R22 is a near match for 295/40R21; 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.

295/40R21 vs 305/35R22 differences
Measurement	295/40R21	305/35R22	Difference	% diff
Overall diameter	30.29 in (769.4 mm)	30.41 in (772.3 mm)	+0.11 in (+2.9 mm)	+0.38%
Sidewall height	4.65 in (118.0 mm)	4.20 in (106.8 mm)	−0.44 in (−11.2 mm)	−9.53%
Section width	11.61 in (295.0 mm)	12.01 in (305.0 mm)	+0.39 in (+10.0 mm)	+3.39%
Circumference	95.16 in (2,417.1 mm)	95.52 in (2,426.3 mm)	+0.36 in (+9.1 mm)	+0.38%
Revolutions per mile	666	663	−3	−0.38%

True speed with the speedometer calibrated for 295/40R21
Indicated	Actual on 295/40R21	Actual on 305/35R22	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: 305/35R22 raises the vehicle by 0.06 in (1.4 mm) at the axle (half the +2.9 mm diameter difference).

305/35R22 is 0.11 in taller than 295/40R21 and 10 mm wider, a 0.38% difference in overall diameter.

With the speedometer calibrated for 295/40R21, an indicated 60 mph is actually 60.2 mph on 305/35R22, and revolutions per mile change from 666 to 663.

305/35R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 295/40R21.

Size pages

Other comparisons with 295/40R21

Other comparisons with 305/35R22

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