295/70R17 vs 285/70R18

285/70R18 is 0.45 in (11.4 mm) taller than 295/70R17, a +1.35% diameter difference. With the speedometer set for 295/70R17, an indicated 60 mph is 60.8 mph on 285/70R18.

Is this a safe swap?

Diameter difference +1.35%: within the ±3% guideline

By overall diameter alone, 285/70R18 falls inside the ±3% range commonly used as a guideline when replacing 295/70R17. 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.

295/70R17 vs 285/70R18 differences
Measurement	295/70R17	285/70R18	Difference	% diff
Overall diameter	33.26 in (844.8 mm)	33.71 in (856.2 mm)	+0.45 in (+11.4 mm)	+1.35%
Sidewall height	8.13 in (206.5 mm)	7.85 in (199.5 mm)	−0.28 in (−7.0 mm)	−3.39%
Section width	11.61 in (295.0 mm)	11.22 in (285.0 mm)	−0.39 in (−10.0 mm)	−3.39%
Circumference	104.49 in (2,654.0 mm)	105.90 in (2,689.8 mm)	+1.41 in (+35.8 mm)	+1.35%
Revolutions per mile	606	598	−8	−1.33%

True speed with the speedometer calibrated for 295/70R17
Indicated	Actual on 295/70R17	Actual on 285/70R18	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: 285/70R18 raises the vehicle by 0.22 in (5.7 mm) at the axle (half the +11.4 mm diameter difference).

285/70R18 is 0.45 in taller than 295/70R17 and 10 mm narrower, a 1.35% difference in overall diameter.

With the speedometer calibrated for 295/70R17, an indicated 60 mph is actually 60.8 mph on 285/70R18, and revolutions per mile change from 606 to 598.

285/70R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 295/70R17.

Size pages

Other comparisons with 295/70R17

Other comparisons with 285/70R18

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