245/45R17 vs 285/35R18

285/35R18 is 0.17 in (4.4 mm) taller than 245/45R17, a +0.67% diameter difference. With the speedometer set for 245/45R17, an indicated 60 mph is 60.4 mph on 285/35R18.

Is this a safe swap?

Diameter difference +0.67%: under 1%

By overall diameter alone, 285/35R18 is a near match for 245/45R17; 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.

245/45R17 vs 285/35R18 differences
Measurement	245/45R17	285/35R18	Difference	% diff
Overall diameter	25.68 in (652.3 mm)	25.85 in (656.7 mm)	+0.17 in (+4.4 mm)	+0.67%
Sidewall height	4.34 in (110.3 mm)	3.93 in (99.8 mm)	−0.41 in (−10.5 mm)	−9.52%
Section width	9.65 in (245.0 mm)	11.22 in (285.0 mm)	+1.57 in (+40.0 mm)	+16.33%
Circumference	80.68 in (2,049.3 mm)	81.22 in (2,063.1 mm)	+0.54 in (+13.8 mm)	+0.67%
Revolutions per mile	785	780	−5	−0.67%

True speed with the speedometer calibrated for 245/45R17
Indicated	Actual on 245/45R17	Actual on 285/35R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 285/35R18 raises the vehicle by 0.09 in (2.2 mm) at the axle (half the +4.4 mm diameter difference).

285/35R18 is 0.17 in taller than 245/45R17 and 40 mm wider, a 0.67% difference in overall diameter.

With the speedometer calibrated for 245/45R17, an indicated 60 mph is actually 60.4 mph on 285/35R18, and revolutions per mile change from 785 to 780.

285/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 245/45R17.

Size pages

Other comparisons with 245/45R17

Other comparisons with 285/35R18

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