225/50R18 vs 235/50R18

235/50R18 is 0.39 in (10.0 mm) taller than 225/50R18, a +1.47% diameter difference. With the speedometer set for 225/50R18, an indicated 60 mph is 60.9 mph on 235/50R18.

Is this a safe swap?

Diameter difference +1.47%: within the ±3% guideline

By overall diameter alone, 235/50R18 falls inside the ±3% range commonly used as a guideline when replacing 225/50R18. 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.

225/50R18 vs 235/50R18 differences
Measurement	225/50R18	235/50R18	Difference	% diff
Overall diameter	26.86 in (682.2 mm)	27.25 in (692.2 mm)	+0.39 in (+10.0 mm)	+1.47%
Sidewall height	4.43 in (112.5 mm)	4.63 in (117.5 mm)	+0.20 in (+5.0 mm)	+4.44%
Section width	8.86 in (225.0 mm)	9.25 in (235.0 mm)	+0.39 in (+10.0 mm)	+4.44%
Circumference	84.38 in (2,143.2 mm)	85.61 in (2,174.6 mm)	+1.24 in (+31.4 mm)	+1.47%
Revolutions per mile	751	740	−11	−1.44%

True speed with the speedometer calibrated for 225/50R18
Indicated	Actual on 225/50R18	Actual on 235/50R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.1 mph	+1.1 mph

Ride-height change: 235/50R18 raises the vehicle by 0.20 in (5.0 mm) at the axle (half the +10.0 mm diameter difference).

235/50R18 is 0.39 in taller than 225/50R18 and 10 mm wider, a 1.47% difference in overall diameter.

With the speedometer calibrated for 225/50R18, an indicated 60 mph is actually 60.9 mph on 235/50R18, and revolutions per mile change from 751 to 740.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 225/50R18

Other comparisons with 235/50R18

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