215/55R16 vs 255/40R17

255/40R17 is 0.28 in (7.1 mm) shorter than 215/55R16, a −1.10% diameter difference. With the speedometer set for 215/55R16, an indicated 60 mph is 59.3 mph on 255/40R17.

Is this a safe swap?

Diameter difference −1.10%: within the ±3% guideline

By overall diameter alone, 255/40R17 falls inside the ±3% range commonly used as a guideline when replacing 215/55R16. 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.

215/55R16 vs 255/40R17 differences
Measurement	215/55R16	255/40R17	Difference	% diff
Overall diameter	25.31 in (642.9 mm)	25.03 in (635.8 mm)	−0.28 in (−7.1 mm)	−1.10%
Sidewall height	4.66 in (118.3 mm)	4.02 in (102.0 mm)	−0.64 in (−16.2 mm)	−13.74%
Section width	8.46 in (215.0 mm)	10.04 in (255.0 mm)	+1.57 in (+40.0 mm)	+18.60%
Circumference	79.52 in (2,019.7 mm)	78.64 in (1,997.4 mm)	−0.88 in (−22.3 mm)	−1.10%
Revolutions per mile	797	806	+9	+1.12%

True speed with the speedometer calibrated for 215/55R16
Indicated	Actual on 215/55R16	Actual on 255/40R17	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.3 mph	−0.7 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 255/40R17 lowers the vehicle by 0.14 in (3.6 mm) at the axle (half the −7.1 mm diameter difference).

255/40R17 is 0.28 in shorter than 215/55R16 and 40 mm wider, a 1.10% difference in overall diameter.

With the speedometer calibrated for 215/55R16, an indicated 60 mph is actually 59.3 mph on 255/40R17, and revolutions per mile change from 797 to 806.

255/40R17 mounts on a 17-inch wheel, a plus-1 fitment from the 16-inch wheel of 215/55R16.

Size pages

Other comparisons with 215/55R16

Other comparisons with 255/40R17

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