TireSizesFinder

31x10.50R16 vs 255/65R18

255/65R18 is 0.05 in (1.3 mm) taller than 31x10.50R16, a +0.17% diameter difference. With the speedometer set for 31x10.50R16, an indicated 60 mph is 60.1 mph on 255/65R18.

Is this a safe swap?

Diameter difference +0.17%: under 1%

By overall diameter alone, 255/65R18 is a near match for 31x10.50R16; 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: 31x10.50R16 (31.00 in) vs 255/65R18 (31.05 in)31x10.50R1631.00 in × 10.50 in255/65R1831.05 in × 10.04 in
Side profile and tread width, drawn to the same scale.
31x10.50R16 vs 255/65R18 differences
Measurement31x10.50R16255/65R18Difference% diff
Overall diameter31.00 in (787.4 mm)31.05 in (788.7 mm)+0.05 in (+1.3 mm)+0.17%
Sidewall height7.50 in (190.5 mm)6.53 in (165.8 mm)−0.97 in (−24.7 mm)−12.99%
Section width10.50 in (266.7 mm)10.04 in (255.0 mm)−0.46 in (−11.7 mm)−4.39%
Circumference97.39 in (2,473.7 mm)97.55 in (2,477.8 mm)+0.16 in (+4.1 mm)+0.17%
Revolutions per mile651650−1−0.16%
True speed with the speedometer calibrated for 31x10.50R16
IndicatedActual on 31x10.50R16Actual on 255/65R18Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 255/65R18 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.3 mm diameter difference).

255/65R18 is 0.05 in taller than 31x10.50R16 and 12 mm narrower, a 0.17% difference in overall diameter.

With the speedometer calibrated for 31x10.50R16, an indicated 60 mph is actually 60.1 mph on 255/65R18, and revolutions per mile change from 651 to 650.

255/65R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 31x10.50R16.

Size pages

Other comparisons with 31x10.50R16

Other comparisons with 255/65R18

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