265/60R17 vs 235/60R18

235/60R18 is 0.42 in (10.6 mm) shorter than 265/60R17, a −1.41% diameter difference. With the speedometer set for 265/60R17, an indicated 60 mph is 59.2 mph on 235/60R18.

Is this a safe swap?

Diameter difference −1.41%: within the ±3% guideline

By overall diameter alone, 235/60R18 falls inside the ±3% range commonly used as a guideline when replacing 265/60R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

265/60R17 vs 235/60R18 differences
Measurement	265/60R17	235/60R18	Difference	% diff
Overall diameter	29.52 in (749.8 mm)	29.10 in (739.2 mm)	−0.42 in (−10.6 mm)	−1.41%
Sidewall height	6.26 in (159.0 mm)	5.55 in (141.0 mm)	−0.71 in (−18.0 mm)	−11.32%
Section width	10.43 in (265.0 mm)	9.25 in (235.0 mm)	−1.18 in (−30.0 mm)	−11.32%
Circumference	92.74 in (2,355.6 mm)	91.43 in (2,322.3 mm)	−1.31 in (−33.3 mm)	−1.41%
Revolutions per mile	683	693	+10	+1.43%

True speed with the speedometer calibrated for 265/60R17
Indicated	Actual on 265/60R17	Actual on 235/60R18	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.2 mph	−0.8 mph
75 mph	75.0 mph	73.9 mph	−1.1 mph

Ride-height change: 235/60R18 lowers the vehicle by 0.21 in (5.3 mm) at the axle (half the −10.6 mm diameter difference).

235/60R18 is 0.42 in shorter than 265/60R17 and 30 mm narrower, a 1.41% difference in overall diameter.

With the speedometer calibrated for 265/60R17, an indicated 60 mph is actually 59.2 mph on 235/60R18, and revolutions per mile change from 683 to 693.

235/60R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 265/60R17.

Size pages

Other comparisons with 265/60R17

Other comparisons with 235/60R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.