TireSizesFinder

215/50R17 vs 215/45R18

215/45R18 is 0.15 in (3.9 mm) taller than 215/50R17, a +0.60% diameter difference. With the speedometer set for 215/50R17, an indicated 60 mph is 60.4 mph on 215/45R18.

Is this a safe swap?

Diameter difference +0.60%: under 1%

By overall diameter alone, 215/45R18 is a near match for 215/50R17; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 215/50R17 (25.46 in) vs 215/45R18 (25.62 in)215/50R1725.46 in × 8.46 in215/45R1825.62 in × 8.46 in
Side profile and tread width, drawn to the same scale.
215/50R17 vs 215/45R18 differences
Measurement215/50R17215/45R18Difference% diff
Overall diameter25.46 in (646.8 mm)25.62 in (650.7 mm)+0.15 in (+3.9 mm)+0.60%
Sidewall height4.23 in (107.5 mm)3.81 in (96.8 mm)−0.42 in (−10.7 mm)−10.00%
Section width8.46 in (215.0 mm)8.46 in (215.0 mm)0.00 in (0.0 mm)0.00%
Circumference80.00 in (2,032.0 mm)80.48 in (2,044.2 mm)+0.48 in (+12.3 mm)+0.60%
Revolutions per mile792787−5−0.60%
True speed with the speedometer calibrated for 215/50R17
IndicatedActual on 215/50R17Actual on 215/45R18Difference
30 mph30.0 mph30.2 mph+0.2 mph
60 mph60.0 mph60.4 mph+0.4 mph
75 mph75.0 mph75.5 mph+0.5 mph

Ride-height change: 215/45R18 raises the vehicle by 0.08 in (2.0 mm) at the axle (half the +3.9 mm diameter difference).

215/45R18 is 0.15 in taller than 215/50R17 and the same width, a 0.60% difference in overall diameter.

With the speedometer calibrated for 215/50R17, an indicated 60 mph is actually 60.4 mph on 215/45R18, and revolutions per mile change from 792 to 787.

215/45R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 215/50R17.

Size pages

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