TireSizesFinder

215/65R17 vs 275/45R18

275/45R18 is 0.26 in (6.6 mm) shorter than 215/65R17, a −0.93% diameter difference. With the speedometer set for 215/65R17, an indicated 60 mph is 59.4 mph on 275/45R18.

Is this a safe swap?

Diameter difference −0.93%: under 1%

By overall diameter alone, 275/45R18 is a near match for 215/65R17; 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: 215/65R17 (28.00 in) vs 275/45R18 (27.74 in)215/65R1728.00 in × 8.46 in275/45R1827.74 in × 10.83 in
Side profile and tread width, drawn to the same scale.
215/65R17 vs 275/45R18 differences
Measurement215/65R17275/45R18Difference% diff
Overall diameter28.00 in (711.3 mm)27.74 in (704.7 mm)−0.26 in (−6.6 mm)−0.93%
Sidewall height5.50 in (139.8 mm)4.87 in (123.8 mm)−0.63 in (−16.0 mm)−11.45%
Section width8.46 in (215.0 mm)10.83 in (275.0 mm)+2.36 in (+60.0 mm)+27.91%
Circumference87.98 in (2,234.6 mm)87.16 in (2,213.9 mm)−0.82 in (−20.7 mm)−0.93%
Revolutions per mile720727+7+0.94%
True speed with the speedometer calibrated for 215/65R17
IndicatedActual on 215/65R17Actual on 275/45R18Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 275/45R18 lowers the vehicle by 0.13 in (3.3 mm) at the axle (half the −6.6 mm diameter difference).

275/45R18 is 0.26 in shorter than 215/65R17 and 60 mm wider, a 0.93% difference in overall diameter.

With the speedometer calibrated for 215/65R17, an indicated 60 mph is actually 59.4 mph on 275/45R18, and revolutions per mile change from 720 to 727.

275/45R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 215/65R17.

Size pages

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