275/70R18 vs 285/70R18

285/70R18 is 0.55 in (14.0 mm) taller than 275/70R18, a +1.66% diameter difference. With the speedometer set for 275/70R18, an indicated 60 mph is 61.0 mph on 285/70R18.

Is this a safe swap?

Diameter difference +1.66%: within the ±3% guideline

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

275/70R18 vs 285/70R18 differences
Measurement	275/70R18	285/70R18	Difference	% diff
Overall diameter	33.16 in (842.2 mm)	33.71 in (856.2 mm)	+0.55 in (+14.0 mm)	+1.66%
Sidewall height	7.58 in (192.5 mm)	7.85 in (199.5 mm)	+0.28 in (+7.0 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	104.17 in (2,645.8 mm)	105.90 in (2,689.8 mm)	+1.73 in (+44.0 mm)	+1.66%
Revolutions per mile	608	598	−10	−1.64%

True speed with the speedometer calibrated for 275/70R18
Indicated	Actual on 275/70R18	Actual on 285/70R18	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: 285/70R18 raises the vehicle by 0.28 in (7.0 mm) at the axle (half the +14.0 mm diameter difference).

285/70R18 is 0.55 in taller than 275/70R18 and 10 mm wider, a 1.66% difference in overall diameter.

With the speedometer calibrated for 275/70R18, an indicated 60 mph is actually 61.0 mph on 285/70R18, and revolutions per mile change from 608 to 598.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 275/70R18

Other comparisons with 285/70R18

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