255/65R18 vs 285/60R18

285/60R18 is 0.41 in (10.5 mm) taller than 255/65R18, a +1.33% diameter difference. With the speedometer set for 255/65R18, an indicated 60 mph is 60.8 mph on 285/60R18.

Is this a safe swap?

Diameter difference +1.33%: within the ±3% guideline

By overall diameter alone, 285/60R18 falls inside the ±3% range commonly used as a guideline when replacing 255/65R18. 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.

255/65R18 vs 285/60R18 differences
Measurement	255/65R18	285/60R18	Difference	% diff
Overall diameter	31.05 in (788.7 mm)	31.46 in (799.2 mm)	+0.41 in (+10.5 mm)	+1.33%
Sidewall height	6.53 in (165.8 mm)	6.73 in (171.0 mm)	+0.21 in (+5.3 mm)	+3.17%
Section width	10.04 in (255.0 mm)	11.22 in (285.0 mm)	+1.18 in (+30.0 mm)	+11.76%
Circumference	97.55 in (2,477.8 mm)	98.85 in (2,510.8 mm)	+1.30 in (+33.0 mm)	+1.33%
Revolutions per mile	650	641	−9	−1.31%

True speed with the speedometer calibrated for 255/65R18
Indicated	Actual on 255/65R18	Actual on 285/60R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	76.0 mph	+1.0 mph

Ride-height change: 285/60R18 raises the vehicle by 0.21 in (5.3 mm) at the axle (half the +10.5 mm diameter difference).

285/60R18 is 0.41 in taller than 255/65R18 and 30 mm wider, a 1.33% difference in overall diameter.

With the speedometer calibrated for 255/65R18, an indicated 60 mph is actually 60.8 mph on 285/60R18, and revolutions per mile change from 650 to 641.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 255/65R18

Other comparisons with 285/60R18

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