265/55R20 vs 305/40R22

305/40R22 is 0.13 in (3.3 mm) taller than 265/55R20, a +0.41% diameter difference. With the speedometer set for 265/55R20, an indicated 60 mph is 60.2 mph on 305/40R22.

Is this a safe swap?

Diameter difference +0.41%: under 1%

By overall diameter alone, 305/40R22 is a near match for 265/55R20; 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.

265/55R20 vs 305/40R22 differences
Measurement	265/55R20	305/40R22	Difference	% diff
Overall diameter	31.48 in (799.5 mm)	31.61 in (802.8 mm)	+0.13 in (+3.3 mm)	+0.41%
Sidewall height	5.74 in (145.8 mm)	4.80 in (122.0 mm)	−0.94 in (−23.7 mm)	−16.30%
Section width	10.43 in (265.0 mm)	12.01 in (305.0 mm)	+1.57 in (+40.0 mm)	+15.09%
Circumference	98.89 in (2,511.7 mm)	99.29 in (2,522.1 mm)	+0.41 in (+10.4 mm)	+0.41%
Revolutions per mile	641	638	−3	−0.41%

True speed with the speedometer calibrated for 265/55R20
Indicated	Actual on 265/55R20	Actual on 305/40R22	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: 305/40R22 raises the vehicle by 0.06 in (1.6 mm) at the axle (half the +3.3 mm diameter difference).

305/40R22 is 0.13 in taller than 265/55R20 and 40 mm wider, a 0.41% difference in overall diameter.

With the speedometer calibrated for 265/55R20, an indicated 60 mph is actually 60.2 mph on 305/40R22, and revolutions per mile change from 641 to 638.

305/40R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 265/55R20.

Size pages

Other comparisons with 265/55R20

Other comparisons with 305/40R22

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