235/75R16 vs 255/60R18

255/60R18 is 0.17 in (4.3 mm) taller than 235/75R16, a +0.57% diameter difference. With the speedometer set for 235/75R16, an indicated 60 mph is 60.3 mph on 255/60R18.

Is this a safe swap?

Diameter difference +0.57%: under 1%

By overall diameter alone, 255/60R18 is a near match for 235/75R16; 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.

235/75R16 vs 255/60R18 differences
Measurement	235/75R16	255/60R18	Difference	% diff
Overall diameter	29.88 in (758.9 mm)	30.05 in (763.2 mm)	+0.17 in (+4.3 mm)	+0.57%
Sidewall height	6.94 in (176.3 mm)	6.02 in (153.0 mm)	−0.92 in (−23.2 mm)	−13.19%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	93.86 in (2,384.2 mm)	94.40 in (2,397.7 mm)	+0.53 in (+13.5 mm)	+0.57%
Revolutions per mile	675	671	−4	−0.56%

True speed with the speedometer calibrated for 235/75R16
Indicated	Actual on 235/75R16	Actual on 255/60R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 255/60R18 raises the vehicle by 0.08 in (2.2 mm) at the axle (half the +4.3 mm diameter difference).

255/60R18 is 0.17 in taller than 235/75R16 and 20 mm wider, a 0.57% difference in overall diameter.

With the speedometer calibrated for 235/75R16, an indicated 60 mph is actually 60.3 mph on 255/60R18, and revolutions per mile change from 675 to 671.

255/60R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 235/75R16.

Size pages

Other comparisons with 235/75R16

Other comparisons with 255/60R18

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