32x11.50R15 vs 255/70R17

255/70R17 is 0.94 in (24.0 mm) shorter than 32x11.50R15, a −2.95% diameter difference. With the speedometer set for 32x11.50R15, an indicated 60 mph is 58.2 mph on 255/70R17.

Is this a safe swap?

Diameter difference −2.95%: within the ±3% guideline

By overall diameter alone, 255/70R17 falls inside the ±3% range commonly used as a guideline when replacing 32x11.50R15. 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.

32x11.50R15 vs 255/70R17 differences
Measurement	32x11.50R15	255/70R17	Difference	% diff
Overall diameter	32.00 in (812.8 mm)	31.06 in (788.8 mm)	−0.94 in (−24.0 mm)	−2.95%
Sidewall height	8.50 in (215.9 mm)	7.03 in (178.5 mm)	−1.47 in (−37.4 mm)	−17.32%
Section width	11.50 in (292.1 mm)	10.04 in (255.0 mm)	−1.46 in (−37.1 mm)	−12.70%
Circumference	100.53 in (2,553.5 mm)	97.56 in (2,478.1 mm)	−2.97 in (−75.4 mm)	−2.95%
Revolutions per mile	630	649	+19	+3.04%

True speed with the speedometer calibrated for 32x11.50R15
Indicated	Actual on 32x11.50R15	Actual on 255/70R17	Difference
30 mph	30.0 mph	29.1 mph	−0.9 mph
60 mph	60.0 mph	58.2 mph	−1.8 mph
75 mph	75.0 mph	72.8 mph	−2.2 mph

Ride-height change: 255/70R17 lowers the vehicle by 0.47 in (12.0 mm) at the axle (half the −24.0 mm diameter difference).

255/70R17 is 0.94 in shorter than 32x11.50R15 and 37 mm narrower, a 2.95% difference in overall diameter.

With the speedometer calibrated for 32x11.50R15, an indicated 60 mph is actually 58.2 mph on 255/70R17, and revolutions per mile change from 630 to 649.

255/70R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 32x11.50R15.

Size pages

Other comparisons with 32x11.50R15

Other comparisons with 255/70R17

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