215/65R17 vs 285/45R18

285/45R18 is 0.09 in (2.4 mm) taller than 215/65R17, a +0.34% diameter difference. With the speedometer set for 215/65R17, an indicated 60 mph is 60.2 mph on 285/45R18.

Is this a safe swap?

Diameter difference +0.34%: under 1%

By overall diameter alone, 285/45R18 is a near match for 215/65R17; the speedometer changes by less than 1%. 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.

215/65R17 vs 285/45R18 differences
Measurement	215/65R17	285/45R18	Difference	% diff
Overall diameter	28.00 in (711.3 mm)	28.10 in (713.7 mm)	+0.09 in (+2.4 mm)	+0.34%
Sidewall height	5.50 in (139.8 mm)	5.05 in (128.3 mm)	−0.45 in (−11.5 mm)	−8.23%
Section width	8.46 in (215.0 mm)	11.22 in (285.0 mm)	+2.76 in (+70.0 mm)	+32.56%
Circumference	87.98 in (2,234.6 mm)	88.27 in (2,242.2 mm)	+0.30 in (+7.5 mm)	+0.34%
Revolutions per mile	720	718	−2	−0.34%

True speed with the speedometer calibrated for 215/65R17
Indicated	Actual on 215/65R17	Actual on 285/45R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.3 mph	+0.3 mph

Ride-height change: 285/45R18 raises the vehicle by 0.05 in (1.2 mm) at the axle (half the +2.4 mm diameter difference).

285/45R18 is 0.09 in taller than 215/65R17 and 70 mm wider, a 0.34% difference in overall diameter.

With the speedometer calibrated for 215/65R17, an indicated 60 mph is actually 60.2 mph on 285/45R18, and revolutions per mile change from 720 to 718.

285/45R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 215/65R17.

Size pages

Other comparisons with 215/65R17

Other comparisons with 285/45R18

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