TireSizesFinder

225/55R18 vs 275/45R18

275/45R18 is 0.00 in (0.0 mm) taller than 225/55R18, a 0.00% diameter difference. With the speedometer set for 225/55R18, an indicated 60 mph is 60.0 mph on 275/45R18.

Is this a safe swap?

Diameter difference 0.00%: under 1%

By overall diameter alone, 275/45R18 is a near match for 225/55R18; 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: 225/55R18 (27.74 in) vs 275/45R18 (27.74 in)225/55R1827.74 in × 8.86 in275/45R1827.74 in × 10.83 in
Side profile and tread width, drawn to the same scale.
225/55R18 vs 275/45R18 differences
Measurement225/55R18275/45R18Difference% diff
Overall diameter27.74 in (704.7 mm)27.74 in (704.7 mm)0.00 in (0.0 mm)0.00%
Sidewall height4.87 in (123.8 mm)4.87 in (123.8 mm)0.00 in (0.0 mm)0.00%
Section width8.86 in (225.0 mm)10.83 in (275.0 mm)+1.97 in (+50.0 mm)+22.22%
Circumference87.16 in (2,213.9 mm)87.16 in (2,213.9 mm)0.00 in (0.0 mm)0.00%
Revolutions per mile72772700.00%
True speed with the speedometer calibrated for 225/55R18
IndicatedActual on 225/55R18Actual on 275/45R18Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.0 mph0.0 mph
75 mph75.0 mph75.0 mph0.0 mph

Ride-height change: 275/45R18 does not change the vehicle at the axle (half the 0.0 mm diameter difference).

275/45R18 is the same height as 225/55R18 and 50 mm wider, a 0.00% difference in overall diameter.

With the speedometer calibrated for 225/55R18, an indicated 60 mph is actually 60.0 mph on 275/45R18, and revolutions per mile change from 727 to 727.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 225/55R18

Other comparisons with 275/45R18

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