215/60R15 vs 255/40R17

255/40R17 is 0.13 in (3.2 mm) shorter than 215/60R15, a −0.50% diameter difference. With the speedometer set for 215/60R15, an indicated 60 mph is 59.7 mph on 255/40R17.

Is this a safe swap?

Diameter difference −0.50%: under 1%

By overall diameter alone, 255/40R17 is a near match for 215/60R15; the speedometer changes by less than 1%. 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.

215/60R15 vs 255/40R17 differences
Measurement	215/60R15	255/40R17	Difference	% diff
Overall diameter	25.16 in (639.0 mm)	25.03 in (635.8 mm)	−0.13 in (−3.2 mm)	−0.50%
Sidewall height	5.08 in (129.0 mm)	4.02 in (102.0 mm)	−1.06 in (−27.0 mm)	−20.93%
Section width	8.46 in (215.0 mm)	10.04 in (255.0 mm)	+1.57 in (+40.0 mm)	+18.60%
Circumference	79.03 in (2,007.5 mm)	78.64 in (1,997.4 mm)	−0.40 in (−10.1 mm)	−0.50%
Revolutions per mile	802	806	+4	+0.50%

True speed with the speedometer calibrated for 215/60R15
Indicated	Actual on 215/60R15	Actual on 255/40R17	Difference
30 mph	30.0 mph	29.8 mph	−0.2 mph
60 mph	60.0 mph	59.7 mph	−0.3 mph
75 mph	75.0 mph	74.6 mph	−0.4 mph

Ride-height change: 255/40R17 lowers the vehicle by 0.06 in (1.6 mm) at the axle (half the −3.2 mm diameter difference).

255/40R17 is 0.13 in shorter than 215/60R15 and 40 mm wider, a 0.50% difference in overall diameter.

With the speedometer calibrated for 215/60R15, an indicated 60 mph is actually 59.7 mph on 255/40R17, and revolutions per mile change from 802 to 806.

255/40R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 215/60R15.

Size pages

Other comparisons with 215/60R15

Other comparisons with 255/40R17

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