285/65R17 vs 275/65R18

275/65R18 is 0.49 in (12.4 mm) taller than 285/65R17, a +1.55% diameter difference. With the speedometer set for 285/65R17, an indicated 60 mph is 60.9 mph on 275/65R18.

Is this a safe swap?

Diameter difference +1.55%: within the ±3% guideline

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

285/65R17 vs 275/65R18 differences
Measurement	285/65R17	275/65R18	Difference	% diff
Overall diameter	31.59 in (802.3 mm)	32.07 in (814.7 mm)	+0.49 in (+12.4 mm)	+1.55%
Sidewall height	7.29 in (185.3 mm)	7.04 in (178.8 mm)	−0.26 in (−6.5 mm)	−3.51%
Section width	11.22 in (285.0 mm)	10.83 in (275.0 mm)	−0.39 in (−10.0 mm)	−3.51%
Circumference	99.23 in (2,520.5 mm)	100.77 in (2,559.5 mm)	+1.53 in (+39.0 mm)	+1.55%
Revolutions per mile	639	629	−10	−1.52%

True speed with the speedometer calibrated for 285/65R17
Indicated	Actual on 285/65R17	Actual on 275/65R18	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.2 mph	+1.2 mph

Ride-height change: 275/65R18 raises the vehicle by 0.24 in (6.2 mm) at the axle (half the +12.4 mm diameter difference).

275/65R18 is 0.49 in taller than 285/65R17 and 10 mm narrower, a 1.55% difference in overall diameter.

With the speedometer calibrated for 285/65R17, an indicated 60 mph is actually 60.9 mph on 275/65R18, and revolutions per mile change from 639 to 629.

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

Size pages

Other comparisons with 285/65R17

Other comparisons with 275/65R18

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