TireSizesFinder

265/60R18 vs 235/55R20

235/55R20 is 0.34 in (8.7 mm) shorter than 265/60R18, a −1.12% diameter difference. With the speedometer set for 265/60R18, an indicated 60 mph is 59.3 mph on 235/55R20.

Is this a safe swap?

Diameter difference −1.12%: within the ±3% guideline

By overall diameter alone, 235/55R20 falls inside the ±3% range commonly used as a guideline when replacing 265/60R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 265/60R18 (30.52 in) vs 235/55R20 (30.18 in)265/60R1830.52 in × 10.43 in235/55R2030.18 in × 9.25 in
Side profile and tread width, drawn to the same scale.
265/60R18 vs 235/55R20 differences
Measurement265/60R18235/55R20Difference% diff
Overall diameter30.52 in (775.2 mm)30.18 in (766.5 mm)−0.34 in (−8.7 mm)−1.12%
Sidewall height6.26 in (159.0 mm)5.09 in (129.3 mm)−1.17 in (−29.7 mm)−18.71%
Section width10.43 in (265.0 mm)9.25 in (235.0 mm)−1.18 in (−30.0 mm)−11.32%
Circumference95.88 in (2,435.4 mm)94.80 in (2,408.0 mm)−1.08 in (−27.3 mm)−1.12%
Revolutions per mile661668+8+1.14%
True speed with the speedometer calibrated for 265/60R18
IndicatedActual on 265/60R18Actual on 235/55R20Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.3 mph−0.7 mph
75 mph75.0 mph74.2 mph−0.8 mph

Ride-height change: 235/55R20 lowers the vehicle by 0.17 in (4.4 mm) at the axle (half the −8.7 mm diameter difference).

235/55R20 is 0.34 in shorter than 265/60R18 and 30 mm narrower, a 1.12% difference in overall diameter.

With the speedometer calibrated for 265/60R18, an indicated 60 mph is actually 59.3 mph on 235/55R20, and revolutions per mile change from 661 to 668.

235/55R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 265/60R18.

Size pages

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