225/50R17 vs 285/35R18

285/35R18 is 0.00 in (0.1 mm) shorter than 225/50R17, a −0.02% diameter difference. With the speedometer set for 225/50R17, an indicated 60 mph is 60.0 mph on 285/35R18.

Is this a safe swap?

Diameter difference −0.02%: under 1%

By overall diameter alone, 285/35R18 is a near match for 225/50R17; 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.

225/50R17 vs 285/35R18 differences
Measurement	225/50R17	285/35R18	Difference	% diff
Overall diameter	25.86 in (656.8 mm)	25.85 in (656.7 mm)	0.00 in (−0.1 mm)	−0.02%
Sidewall height	4.43 in (112.5 mm)	3.93 in (99.8 mm)	−0.50 in (−12.7 mm)	−11.33%
Section width	8.86 in (225.0 mm)	11.22 in (285.0 mm)	+2.36 in (+60.0 mm)	+26.67%
Circumference	81.24 in (2,063.4 mm)	81.22 in (2,063.1 mm)	−0.01 in (−0.3 mm)	−0.02%
Revolutions per mile	780	780	0	+0.02%

True speed with the speedometer calibrated for 225/50R17
Indicated	Actual on 225/50R17	Actual on 285/35R18
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 285/35R18 does not change the vehicle at the axle (half the −0.1 mm diameter difference).

285/35R18 is the same height as 225/50R17 and 60 mm wider, a 0.02% difference in overall diameter.

With the speedometer calibrated for 225/50R17, an indicated 60 mph is actually 60.0 mph on 285/35R18, and revolutions per mile change from 780 to 780.

285/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 225/50R17.

Size pages

Other comparisons with 225/50R17

Other comparisons with 285/35R18

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