TireSizesFinder

205/55R17 vs 285/35R18

285/35R18 is 0.02 in (0.6 mm) shorter than 205/55R17, a −0.09% diameter difference. With the speedometer set for 205/55R17, an indicated 60 mph is 59.9 mph on 285/35R18.

Is this a safe swap?

Diameter difference −0.09%: under 1%

By overall diameter alone, 285/35R18 is a near match for 205/55R17; 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: 205/55R17 (25.88 in) vs 285/35R18 (25.85 in)205/55R1725.88 in × 8.07 in285/35R1825.85 in × 11.22 in
Side profile and tread width, drawn to the same scale.
205/55R17 vs 285/35R18 differences
Measurement205/55R17285/35R18Difference% diff
Overall diameter25.88 in (657.3 mm)25.85 in (656.7 mm)−0.02 in (−0.6 mm)−0.09%
Sidewall height4.44 in (112.8 mm)3.93 in (99.8 mm)−0.51 in (−13.0 mm)−11.53%
Section width8.07 in (205.0 mm)11.22 in (285.0 mm)+3.15 in (+80.0 mm)+39.02%
Circumference81.30 in (2,065.0 mm)81.22 in (2,063.1 mm)−0.07 in (−1.9 mm)−0.09%
Revolutions per mile779780+1+0.09%
True speed with the speedometer calibrated for 205/55R17
IndicatedActual on 205/55R17Actual on 285/35R18Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.9 mph−0.1 mph

Ride-height change: 285/35R18 lowers the vehicle by 0.01 in (0.3 mm) at the axle (half the −0.6 mm diameter difference).

285/35R18 is 0.02 in shorter than 205/55R17 and 80 mm wider, a 0.09% difference in overall diameter.

With the speedometer calibrated for 205/55R17, an indicated 60 mph is actually 59.9 mph on 285/35R18, and revolutions per mile change from 779 to 780.

285/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 205/55R17.

Size pages

Other comparisons with 205/55R17

Other comparisons with 285/35R18

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