TireSizesFinder

285/70R17 vs 285/65R18

285/65R18 is 0.12 in (3.1 mm) shorter than 285/70R17, a −0.37% diameter difference. With the speedometer set for 285/70R17, an indicated 60 mph is 59.8 mph on 285/65R18.

Is this a safe swap?

Diameter difference −0.37%: under 1%

By overall diameter alone, 285/65R18 is a near match for 285/70R17; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 285/70R17 (32.71 in) vs 285/65R18 (32.59 in)285/70R1732.71 in × 11.22 in285/65R1832.59 in × 11.22 in
Side profile and tread width, drawn to the same scale.
285/70R17 vs 285/65R18 differences
Measurement285/70R17285/65R18Difference% diff
Overall diameter32.71 in (830.8 mm)32.59 in (827.7 mm)−0.12 in (−3.1 mm)−0.37%
Sidewall height7.85 in (199.5 mm)7.29 in (185.3 mm)−0.56 in (−14.2 mm)−7.14%
Section width11.22 in (285.0 mm)11.22 in (285.0 mm)0.00 in (0.0 mm)0.00%
Circumference102.76 in (2,610.0 mm)102.37 in (2,600.3 mm)−0.38 in (−9.7 mm)−0.37%
Revolutions per mile617619+2+0.37%
True speed with the speedometer calibrated for 285/70R17
IndicatedActual on 285/70R17Actual on 285/65R18Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.7 mph−0.3 mph

Ride-height change: 285/65R18 lowers the vehicle by 0.06 in (1.5 mm) at the axle (half the −3.1 mm diameter difference).

285/65R18 is 0.12 in shorter than 285/70R17 and the same width, a 0.37% difference in overall diameter.

With the speedometer calibrated for 285/70R17, an indicated 60 mph is actually 59.8 mph on 285/65R18, and revolutions per mile change from 617 to 619.

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

Size pages

Other comparisons with 285/70R17

Other comparisons with 285/65R18

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.