TireSizesFinder

31x10.50R15 vs 255/70R17

255/70R17 is 0.06 in (1.4 mm) taller than 31x10.50R15, a +0.18% diameter difference. With the speedometer set for 31x10.50R15, an indicated 60 mph is 60.1 mph on 255/70R17.

Is this a safe swap?

Diameter difference +0.18%: under 1%

By overall diameter alone, 255/70R17 is a near match for 31x10.50R15; 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: 31x10.50R15 (31.00 in) vs 255/70R17 (31.06 in)31x10.50R1531.00 in × 10.50 in255/70R1731.06 in × 10.04 in
Side profile and tread width, drawn to the same scale.
31x10.50R15 vs 255/70R17 differences
Measurement31x10.50R15255/70R17Difference% diff
Overall diameter31.00 in (787.4 mm)31.06 in (788.8 mm)+0.06 in (+1.4 mm)+0.18%
Sidewall height8.00 in (203.2 mm)7.03 in (178.5 mm)−0.97 in (−24.7 mm)−12.16%
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)97.56 in (2,478.1 mm)+0.17 in (+4.4 mm)+0.18%
Revolutions per mile651649−1−0.18%
True speed with the speedometer calibrated for 31x10.50R15
IndicatedActual on 31x10.50R15Actual on 255/70R17Difference
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: 255/70R17 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

255/70R17 is 0.06 in taller than 31x10.50R15 and 12 mm narrower, a 0.18% difference in overall diameter.

With the speedometer calibrated for 31x10.50R15, an indicated 60 mph is actually 60.1 mph on 255/70R17, and revolutions per mile change from 651 to 649.

255/70R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 31x10.50R15.

Size pages

Other comparisons with 31x10.50R15

Other comparisons with 255/70R17

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