TireSizesFinder

255/60R17 vs 235/60R18

235/60R18 is 0.06 in (1.4 mm) taller than 255/60R17, a +0.19% diameter difference. With the speedometer set for 255/60R17, an indicated 60 mph is 60.1 mph on 235/60R18.

Is this a safe swap?

Diameter difference +0.19%: under 1%

By overall diameter alone, 235/60R18 is a near match for 255/60R17; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 255/60R17 (29.05 in) vs 235/60R18 (29.10 in)255/60R1729.05 in × 10.04 in235/60R1829.10 in × 9.25 in
Side profile and tread width, drawn to the same scale.
255/60R17 vs 235/60R18 differences
Measurement255/60R17235/60R18Difference% diff
Overall diameter29.05 in (737.8 mm)29.10 in (739.2 mm)+0.06 in (+1.4 mm)+0.19%
Sidewall height6.02 in (153.0 mm)5.55 in (141.0 mm)−0.47 in (−12.0 mm)−7.84%
Section width10.04 in (255.0 mm)9.25 in (235.0 mm)−0.79 in (−20.0 mm)−7.84%
Circumference91.25 in (2,317.9 mm)91.43 in (2,322.3 mm)+0.17 in (+4.4 mm)+0.19%
Revolutions per mile694693−1−0.19%
True speed with the speedometer calibrated for 255/60R17
IndicatedActual on 255/60R17Actual on 235/60R18Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 235/60R18 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

235/60R18 is 0.06 in taller than 255/60R17 and 20 mm narrower, a 0.19% difference in overall diameter.

With the speedometer calibrated for 255/60R17, an indicated 60 mph is actually 60.1 mph on 235/60R18, and revolutions per mile change from 694 to 693.

235/60R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 255/60R17.

Size pages

Other comparisons with 255/60R17

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.