255/70R15 vs 245/60R17

245/60R17 is 0.48 in (12.2 mm) shorter than 255/70R15, a −1.65% diameter difference. With the speedometer set for 255/70R15, an indicated 60 mph is 59.0 mph on 245/60R17.

Is this a safe swap?

Diameter difference −1.65%: within the ±3% guideline

By overall diameter alone, 245/60R17 falls inside the ±3% range commonly used as a guideline when replacing 255/70R15. 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.

255/70R15 vs 245/60R17 differences
Measurement	255/70R15	245/60R17	Difference	% diff
Overall diameter	29.06 in (738.0 mm)	28.57 in (725.8 mm)	−0.48 in (−12.2 mm)	−1.65%
Sidewall height	7.03 in (178.5 mm)	5.79 in (147.0 mm)	−1.24 in (−31.5 mm)	−17.65%
Section width	10.04 in (255.0 mm)	9.65 in (245.0 mm)	−0.39 in (−10.0 mm)	−3.92%
Circumference	91.28 in (2,318.5 mm)	89.77 in (2,280.2 mm)	−1.51 in (−38.3 mm)	−1.65%
Revolutions per mile	694	706	+12	+1.68%

True speed with the speedometer calibrated for 255/70R15
Indicated	Actual on 255/70R15	Actual on 245/60R17	Difference
30 mph	30.0 mph	29.5 mph	−0.5 mph
60 mph	60.0 mph	59.0 mph	−1.0 mph
75 mph	75.0 mph	73.8 mph	−1.2 mph

Ride-height change: 245/60R17 lowers the vehicle by 0.24 in (6.1 mm) at the axle (half the −12.2 mm diameter difference).

245/60R17 is 0.48 in shorter than 255/70R15 and 10 mm narrower, a 1.65% difference in overall diameter.

With the speedometer calibrated for 255/70R15, an indicated 60 mph is actually 59.0 mph on 245/60R17, and revolutions per mile change from 694 to 706.

245/60R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 255/70R15.

Size pages

Other comparisons with 255/70R15

Other comparisons with 245/60R17

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