275/70R17 vs 285/65R18

285/65R18 is 0.43 in (10.9 mm) taller than 275/70R17, a +1.33% diameter difference. With the speedometer set for 275/70R17, an indicated 60 mph is 60.8 mph on 285/65R18.

Is this a safe swap?

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

By overall diameter alone, 285/65R18 falls inside the ±3% range commonly used as a guideline when replacing 275/70R17. 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.

275/70R17 vs 285/65R18 differences
Measurement	275/70R17	285/65R18	Difference	% diff
Overall diameter	32.16 in (816.8 mm)	32.59 in (827.7 mm)	+0.43 in (+10.9 mm)	+1.33%
Sidewall height	7.58 in (192.5 mm)	7.29 in (185.3 mm)	−0.29 in (−7.2 mm)	−3.77%
Section width	10.83 in (275.0 mm)	11.22 in (285.0 mm)	+0.39 in (+10.0 mm)	+3.64%
Circumference	101.03 in (2,566.1 mm)	102.37 in (2,600.3 mm)	+1.35 in (+34.2 mm)	+1.33%
Revolutions per mile	627	619	−8	−1.32%

True speed with the speedometer calibrated for 275/70R17
Indicated	Actual on 275/70R17	Actual on 285/65R18	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: 285/65R18 raises the vehicle by 0.21 in (5.5 mm) at the axle (half the +10.9 mm diameter difference).

285/65R18 is 0.43 in taller than 275/70R17 and 10 mm wider, a 1.33% difference in overall diameter.

With the speedometer calibrated for 275/70R17, an indicated 60 mph is actually 60.8 mph on 285/65R18, and revolutions per mile change from 627 to 619.

285/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 275/70R17.

Size pages

Other comparisons with 275/70R17

Other comparisons with 285/65R18

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