215/85R16 vs 255/60R18

255/60R18 is 0.34 in (8.7 mm) shorter than 215/85R16, a −1.13% diameter difference. With the speedometer set for 215/85R16, an indicated 60 mph is 59.3 mph on 255/60R18.

Is this a safe swap?

Diameter difference −1.13%: within the ±3% guideline

By overall diameter alone, 255/60R18 falls inside the ±3% range commonly used as a guideline when replacing 215/85R16. 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.

215/85R16 vs 255/60R18 differences
Measurement	215/85R16	255/60R18	Difference	% diff
Overall diameter	30.39 in (771.9 mm)	30.05 in (763.2 mm)	−0.34 in (−8.7 mm)	−1.13%
Sidewall height	7.19 in (182.8 mm)	6.02 in (153.0 mm)	−1.17 in (−29.7 mm)	−16.28%
Section width	8.46 in (215.0 mm)	10.04 in (255.0 mm)	+1.57 in (+40.0 mm)	+18.60%
Circumference	95.47 in (2,425.0 mm)	94.40 in (2,397.7 mm)	−1.08 in (−27.3 mm)	−1.13%
Revolutions per mile	664	671	+8	+1.14%

True speed with the speedometer calibrated for 215/85R16
Indicated	Actual on 215/85R16	Actual on 255/60R18	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: 255/60R18 lowers the vehicle by 0.17 in (4.3 mm) at the axle (half the −8.7 mm diameter difference).

255/60R18 is 0.34 in shorter than 215/85R16 and 40 mm wider, a 1.13% difference in overall diameter.

With the speedometer calibrated for 215/85R16, an indicated 60 mph is actually 59.3 mph on 255/60R18, and revolutions per mile change from 664 to 671.

255/60R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/85R16.

Size pages

Other comparisons with 215/85R16

Other comparisons with 255/60R18

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