TireSizesFinder

245/65R16 vs 235/55R18

235/55R18 is 0.36 in (9.2 mm) shorter than 245/65R16, a −1.27% diameter difference. With the speedometer set for 245/65R16, an indicated 60 mph is 59.2 mph on 235/55R18.

Is this a safe swap?

Diameter difference −1.27%: within the ±3% guideline

By overall diameter alone, 235/55R18 falls inside the ±3% range commonly used as a guideline when replacing 245/65R16. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 245/65R16 (28.54 in) vs 235/55R18 (28.18 in)245/65R1628.54 in × 9.65 in235/55R1828.18 in × 9.25 in
Side profile and tread width, drawn to the same scale.
245/65R16 vs 235/55R18 differences
Measurement245/65R16235/55R18Difference% diff
Overall diameter28.54 in (724.9 mm)28.18 in (715.7 mm)−0.36 in (−9.2 mm)−1.27%
Sidewall height6.27 in (159.3 mm)5.09 in (129.3 mm)−1.18 in (−30.0 mm)−18.84%
Section width9.65 in (245.0 mm)9.25 in (235.0 mm)−0.39 in (−10.0 mm)−4.08%
Circumference89.66 in (2,277.3 mm)88.52 in (2,248.4 mm)−1.14 in (−28.9 mm)−1.27%
Revolutions per mile707716+9+1.29%
True speed with the speedometer calibrated for 245/65R16
IndicatedActual on 245/65R16Actual on 235/55R18Difference
30 mph30.0 mph29.6 mph−0.4 mph
60 mph60.0 mph59.2 mph−0.8 mph
75 mph75.0 mph74.0 mph−1.0 mph

Ride-height change: 235/55R18 lowers the vehicle by 0.18 in (4.6 mm) at the axle (half the −9.2 mm diameter difference).

235/55R18 is 0.36 in shorter than 245/65R16 and 10 mm narrower, a 1.27% difference in overall diameter.

With the speedometer calibrated for 245/65R16, an indicated 60 mph is actually 59.2 mph on 235/55R18, and revolutions per mile change from 707 to 716.

235/55R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 245/65R16.

Size pages

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