295/70R18 vs 285/60R20

285/60R20 is 0.80 in (20.2 mm) shorter than 295/70R18, a −2.32% diameter difference. With the speedometer set for 295/70R18, an indicated 60 mph is 58.6 mph on 285/60R20.

Is this a safe swap?

Diameter difference −2.32%: within the ±3% guideline

By overall diameter alone, 285/60R20 falls inside the ±3% range commonly used as a guideline when replacing 295/70R18. 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.

295/70R18 vs 285/60R20 differences
Measurement	295/70R18	285/60R20	Difference	% diff
Overall diameter	34.26 in (870.2 mm)	33.46 in (850.0 mm)	−0.80 in (−20.2 mm)	−2.32%
Sidewall height	8.13 in (206.5 mm)	6.73 in (171.0 mm)	−1.40 in (−35.5 mm)	−17.19%
Section width	11.61 in (295.0 mm)	11.22 in (285.0 mm)	−0.39 in (−10.0 mm)	−3.39%
Circumference	107.63 in (2,733.8 mm)	105.13 in (2,670.4 mm)	−2.50 in (−63.5 mm)	−2.32%
Revolutions per mile	589	603	+14	+2.38%

True speed with the speedometer calibrated for 295/70R18
Indicated	Actual on 295/70R18	Actual on 285/60R20	Difference
30 mph	30.0 mph	29.3 mph	−0.7 mph
60 mph	60.0 mph	58.6 mph	−1.4 mph
75 mph	75.0 mph	73.3 mph	−1.7 mph

Ride-height change: 285/60R20 lowers the vehicle by 0.40 in (10.1 mm) at the axle (half the −20.2 mm diameter difference).

285/60R20 is 0.80 in shorter than 295/70R18 and 10 mm narrower, a 2.32% difference in overall diameter.

With the speedometer calibrated for 295/70R18, an indicated 60 mph is actually 58.6 mph on 285/60R20, and revolutions per mile change from 589 to 603.

285/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/70R18.

Size pages

Other comparisons with 295/70R18

Other comparisons with 285/60R20

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