255/50R21 vs 275/40R22

275/40R22 is 0.38 in (9.6 mm) shorter than 255/50R21, a −1.22% diameter difference. With the speedometer set for 255/50R21, an indicated 60 mph is 59.3 mph on 275/40R22.

Is this a safe swap?

Diameter difference −1.22%: within the ±3% guideline

By overall diameter alone, 275/40R22 falls inside the ±3% range commonly used as a guideline when replacing 255/50R21. 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.

255/50R21 vs 275/40R22 differences
Measurement	255/50R21	275/40R22	Difference	% diff
Overall diameter	31.04 in (788.4 mm)	30.66 in (778.8 mm)	−0.38 in (−9.6 mm)	−1.22%
Sidewall height	5.02 in (127.5 mm)	4.33 in (110.0 mm)	−0.69 in (−17.5 mm)	−13.73%
Section width	10.04 in (255.0 mm)	10.83 in (275.0 mm)	+0.79 in (+20.0 mm)	+7.84%
Circumference	97.51 in (2,476.8 mm)	96.33 in (2,446.7 mm)	−1.19 in (−30.2 mm)	−1.22%
Revolutions per mile	650	658	+8	+1.23%

True speed with the speedometer calibrated for 255/50R21
Indicated	Actual on 255/50R21	Actual on 275/40R22	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.3 mph	−0.7 mph
75 mph	75.0 mph	74.1 mph	−0.9 mph

Ride-height change: 275/40R22 lowers the vehicle by 0.19 in (4.8 mm) at the axle (half the −9.6 mm diameter difference).

275/40R22 is 0.38 in shorter than 255/50R21 and 20 mm wider, a 1.22% difference in overall diameter.

With the speedometer calibrated for 255/50R21, an indicated 60 mph is actually 59.3 mph on 275/40R22, and revolutions per mile change from 650 to 658.

275/40R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 255/50R21.

Size pages

Other comparisons with 255/50R21

Other comparisons with 275/40R22

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