275/65R18 vs 285/65R18

285/65R18 is 0.51 in (13.0 mm) taller than 275/65R18, a +1.60% diameter difference. With the speedometer set for 275/65R18, an indicated 60 mph is 61.0 mph on 285/65R18.

Is this a safe swap?

Diameter difference +1.60%: within the ±3% guideline

By overall diameter alone, 285/65R18 falls inside the ±3% range commonly used as a guideline when replacing 275/65R18. 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.

275/65R18 vs 285/65R18 differences
Measurement	275/65R18	285/65R18	Difference	% diff
Overall diameter	32.07 in (814.7 mm)	32.59 in (827.7 mm)	+0.51 in (+13.0 mm)	+1.60%
Sidewall height	7.04 in (178.8 mm)	7.29 in (185.3 mm)	+0.26 in (+6.5 mm)	+3.64%
Section width	10.83 in (275.0 mm)	11.22 in (285.0 mm)	+0.39 in (+10.0 mm)	+3.64%
Circumference	100.77 in (2,559.5 mm)	102.37 in (2,600.3 mm)	+1.61 in (+40.8 mm)	+1.60%
Revolutions per mile	629	619	−10	−1.57%

True speed with the speedometer calibrated for 275/65R18
Indicated	Actual on 275/65R18	Actual on 285/65R18	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.0 mph	+1.0 mph
75 mph	75.0 mph	76.2 mph	+1.2 mph

Ride-height change: 285/65R18 raises the vehicle by 0.26 in (6.5 mm) at the axle (half the +13.0 mm diameter difference).

285/65R18 is 0.51 in taller than 275/65R18 and 10 mm wider, a 1.60% difference in overall diameter.

With the speedometer calibrated for 275/65R18, an indicated 60 mph is actually 61.0 mph on 285/65R18, and revolutions per mile change from 629 to 619.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 275/65R18

Other comparisons with 285/65R18

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