TireSizesFinder

185/55R16 vs 215/35R18

215/35R18 is 0.09 in (2.2 mm) shorter than 185/55R16, a −0.36% diameter difference. With the speedometer set for 185/55R16, an indicated 60 mph is 59.8 mph on 215/35R18.

Is this a safe swap?

Diameter difference −0.36%: under 1%

By overall diameter alone, 215/35R18 is a near match for 185/55R16; 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: 185/55R16 (24.01 in) vs 215/35R18 (23.93 in)185/55R1624.01 in × 7.28 in215/35R1823.93 in × 8.46 in
Side profile and tread width, drawn to the same scale.
185/55R16 vs 215/35R18 differences
Measurement185/55R16215/35R18Difference% diff
Overall diameter24.01 in (609.9 mm)23.93 in (607.7 mm)−0.09 in (−2.2 mm)−0.36%
Sidewall height4.01 in (101.8 mm)2.96 in (75.3 mm)−1.04 in (−26.5 mm)−26.04%
Section width7.28 in (185.0 mm)8.46 in (215.0 mm)+1.18 in (+30.0 mm)+16.22%
Circumference75.44 in (1,916.1 mm)75.16 in (1,909.1 mm)−0.27 in (−6.9 mm)−0.36%
Revolutions per mile840843+3+0.36%
True speed with the speedometer calibrated for 185/55R16
IndicatedActual on 185/55R16Actual on 215/35R18Difference
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: 215/35R18 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.2 mm diameter difference).

215/35R18 is 0.09 in shorter than 185/55R16 and 30 mm wider, a 0.36% difference in overall diameter.

With the speedometer calibrated for 185/55R16, an indicated 60 mph is actually 59.8 mph on 215/35R18, and revolutions per mile change from 840 to 843.

215/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 185/55R16.

Size pages

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