255/35R21 vs 255/30R22

255/30R22 is 0.00 in (0.1 mm) shorter than 255/35R21, a −0.01% diameter difference. With the speedometer set for 255/35R21, an indicated 60 mph is 60.0 mph on 255/30R22.

Is this a safe swap?

Diameter difference −0.01%: under 1%

By overall diameter alone, 255/30R22 is a near match for 255/35R21; 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.

255/35R21 vs 255/30R22 differences
Measurement	255/35R21	255/30R22	Difference	% diff
Overall diameter	28.03 in (711.9 mm)	28.02 in (711.8 mm)	0.00 in (−0.1 mm)	−0.01%
Sidewall height	3.51 in (89.3 mm)	3.01 in (76.5 mm)	−0.50 in (−12.7 mm)	−14.29%
Section width	10.04 in (255.0 mm)	10.04 in (255.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	88.05 in (2,236.5 mm)	88.04 in (2,236.2 mm)	−0.01 in (−0.3 mm)	−0.01%
Revolutions per mile	720	720	0	+0.01%

True speed with the speedometer calibrated for 255/35R21
Indicated	Actual on 255/35R21	Actual on 255/30R22
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 255/30R22 lowers the vehicle by 0.00 in (0.1 mm) at the axle (half the −0.1 mm diameter difference).

255/30R22 is the same height as 255/35R21 and the same width, a 0.01% difference in overall diameter.

With the speedometer calibrated for 255/35R21, an indicated 60 mph is actually 60.0 mph on 255/30R22, and revolutions per mile change from 720 to 720.

255/30R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 255/35R21.

Size pages

Other comparisons with 255/35R21

Other comparisons with 255/30R22

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