245/75R16 vs 255/60R18

255/60R18 is 0.42 in (10.7 mm) shorter than 245/75R16, a −1.38% diameter difference. With the speedometer set for 245/75R16, an indicated 60 mph is 59.2 mph on 255/60R18.

Is this a safe swap?

Diameter difference −1.38%: within the ±3% guideline

By overall diameter alone, 255/60R18 falls inside the ±3% range commonly used as a guideline when replacing 245/75R16. 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.

245/75R16 vs 255/60R18 differences
Measurement	245/75R16	255/60R18	Difference	% diff
Overall diameter	30.47 in (773.9 mm)	30.05 in (763.2 mm)	−0.42 in (−10.7 mm)	−1.38%
Sidewall height	7.23 in (183.8 mm)	6.02 in (153.0 mm)	−1.21 in (−30.7 mm)	−16.73%
Section width	9.65 in (245.0 mm)	10.04 in (255.0 mm)	+0.39 in (+10.0 mm)	+4.08%
Circumference	95.72 in (2,431.3 mm)	94.40 in (2,397.7 mm)	−1.32 in (−33.6 mm)	−1.38%
Revolutions per mile	662	671	+9	+1.40%

True speed with the speedometer calibrated for 245/75R16
Indicated	Actual on 245/75R16	Actual on 255/60R18	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.2 mph	−0.8 mph
75 mph	75.0 mph	74.0 mph	−1.0 mph

Ride-height change: 255/60R18 lowers the vehicle by 0.21 in (5.3 mm) at the axle (half the −10.7 mm diameter difference).

255/60R18 is 0.42 in shorter than 245/75R16 and 10 mm wider, a 1.38% difference in overall diameter.

With the speedometer calibrated for 245/75R16, an indicated 60 mph is actually 59.2 mph on 255/60R18, and revolutions per mile change from 662 to 671.

255/60R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 245/75R16.

Size pages

Other comparisons with 245/75R16

Other comparisons with 255/60R18

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