215/35R18 vs 225/35R18

225/35R18 is 0.28 in (7.0 mm) taller than 215/35R18, a +1.15% diameter difference. With the speedometer set for 215/35R18, an indicated 60 mph is 60.7 mph on 225/35R18.

Is this a safe swap?

Diameter difference +1.15%: within the ±3% guideline

By overall diameter alone, 225/35R18 falls inside the ±3% range commonly used as a guideline when replacing 215/35R18. 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.

215/35R18 vs 225/35R18 differences
Measurement	215/35R18	225/35R18	Difference	% diff
Overall diameter	23.93 in (607.7 mm)	24.20 in (614.7 mm)	+0.28 in (+7.0 mm)	+1.15%
Sidewall height	2.96 in (75.3 mm)	3.10 in (78.8 mm)	+0.14 in (+3.5 mm)	+4.65%
Section width	8.46 in (215.0 mm)	8.86 in (225.0 mm)	+0.39 in (+10.0 mm)	+4.65%
Circumference	75.16 in (1,909.1 mm)	76.03 in (1,931.1 mm)	+0.87 in (+22.0 mm)	+1.15%
Revolutions per mile	843	833	−10	−1.14%

True speed with the speedometer calibrated for 215/35R18
Indicated	Actual on 215/35R18	Actual on 225/35R18	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.7 mph	+0.7 mph
75 mph	75.0 mph	75.9 mph	+0.9 mph

Ride-height change: 225/35R18 raises the vehicle by 0.14 in (3.5 mm) at the axle (half the +7.0 mm diameter difference).

225/35R18 is 0.28 in taller than 215/35R18 and 10 mm wider, a 1.15% difference in overall diameter.

With the speedometer calibrated for 215/35R18, an indicated 60 mph is actually 60.7 mph on 225/35R18, and revolutions per mile change from 843 to 833.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 215/35R18

Other comparisons with 225/35R18

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