285/40R22 vs 305/40R22

305/40R22 is 0.63 in (16.0 mm) taller than 285/40R22, a +2.03% diameter difference. With the speedometer set for 285/40R22, an indicated 60 mph is 61.2 mph on 305/40R22.

Is this a safe swap?

Diameter difference +2.03%: within the ±3% guideline

By overall diameter alone, 305/40R22 falls inside the ±3% range commonly used as a guideline when replacing 285/40R22. 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.

285/40R22 vs 305/40R22 differences
Measurement	285/40R22	305/40R22	Difference	% diff
Overall diameter	30.98 in (786.8 mm)	31.61 in (802.8 mm)	+0.63 in (+16.0 mm)	+2.03%
Sidewall height	4.49 in (114.0 mm)	4.80 in (122.0 mm)	+0.31 in (+8.0 mm)	+7.02%
Section width	11.22 in (285.0 mm)	12.01 in (305.0 mm)	+0.79 in (+20.0 mm)	+7.02%
Circumference	97.32 in (2,471.8 mm)	99.29 in (2,522.1 mm)	+1.98 in (+50.3 mm)	+2.03%
Revolutions per mile	651	638	−13	−1.99%

True speed with the speedometer calibrated for 285/40R22
Indicated	Actual on 285/40R22	Actual on 305/40R22	Difference
30 mph	30.0 mph	30.6 mph	+0.6 mph
60 mph	60.0 mph	61.2 mph	+1.2 mph
75 mph	75.0 mph	76.5 mph	+1.5 mph

Ride-height change: 305/40R22 raises the vehicle by 0.31 in (8.0 mm) at the axle (half the +16.0 mm diameter difference).

305/40R22 is 0.63 in taller than 285/40R22 and 20 mm wider, a 2.03% difference in overall diameter.

With the speedometer calibrated for 285/40R22, an indicated 60 mph is actually 61.2 mph on 305/40R22, and revolutions per mile change from 651 to 638.

Both sizes mount on 22-inch wheels.

Size pages

Other comparisons with 285/40R22

Other comparisons with 305/40R22

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