235/45R21 vs 255/35R22

255/35R22 is 0.30 in (7.6 mm) shorter than 235/45R21, a −1.02% diameter difference. With the speedometer set for 235/45R21, an indicated 60 mph is 59.4 mph on 255/35R22.

Is this a safe swap?

Diameter difference −1.02%: within the ±3% guideline

By overall diameter alone, 255/35R22 falls inside the ±3% range commonly used as a guideline when replacing 235/45R21. 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.

235/45R21 vs 255/35R22 differences
Measurement	235/45R21	255/35R22	Difference	% diff
Overall diameter	29.33 in (744.9 mm)	29.03 in (737.3 mm)	−0.30 in (−7.6 mm)	−1.02%
Sidewall height	4.16 in (105.8 mm)	3.51 in (89.3 mm)	−0.65 in (−16.5 mm)	−15.60%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	92.13 in (2,340.2 mm)	91.19 in (2,316.3 mm)	−0.94 in (−23.9 mm)	−1.02%
Revolutions per mile	688	695	+7	+1.03%

True speed with the speedometer calibrated for 235/45R21
Indicated	Actual on 235/45R21	Actual on 255/35R22	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.4 mph	−0.6 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 255/35R22 lowers the vehicle by 0.15 in (3.8 mm) at the axle (half the −7.6 mm diameter difference).

255/35R22 is 0.30 in shorter than 235/45R21 and 20 mm wider, a 1.02% difference in overall diameter.

With the speedometer calibrated for 235/45R21, an indicated 60 mph is actually 59.4 mph on 255/35R22, and revolutions per mile change from 688 to 695.

255/35R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 235/45R21.

Size pages

Other comparisons with 235/45R21

Other comparisons with 255/35R22

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