245/65R17 vs 235/60R18

235/60R18 is 0.44 in (11.1 mm) shorter than 245/65R17, a −1.48% diameter difference. With the speedometer set for 245/65R17, an indicated 60 mph is 59.1 mph on 235/60R18.

Is this a safe swap?

Diameter difference −1.48%: within the ±3% guideline

By overall diameter alone, 235/60R18 falls inside the ±3% range commonly used as a guideline when replacing 245/65R17. 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.

245/65R17 vs 235/60R18 differences
Measurement	245/65R17	235/60R18	Difference	% diff
Overall diameter	29.54 in (750.3 mm)	29.10 in (739.2 mm)	−0.44 in (−11.1 mm)	−1.48%
Sidewall height	6.27 in (159.3 mm)	5.55 in (141.0 mm)	−0.72 in (−18.2 mm)	−11.46%
Section width	9.65 in (245.0 mm)	9.25 in (235.0 mm)	−0.39 in (−10.0 mm)	−4.08%
Circumference	92.80 in (2,357.1 mm)	91.43 in (2,322.3 mm)	−1.37 in (−34.9 mm)	−1.48%
Revolutions per mile	683	693	+10	+1.50%

True speed with the speedometer calibrated for 245/65R17
Indicated	Actual on 245/65R17	Actual on 235/60R18	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.1 mph	−0.9 mph
75 mph	75.0 mph	73.9 mph	−1.1 mph

Ride-height change: 235/60R18 lowers the vehicle by 0.22 in (5.5 mm) at the axle (half the −11.1 mm diameter difference).

235/60R18 is 0.44 in shorter than 245/65R17 and 10 mm narrower, a 1.48% difference in overall diameter.

With the speedometer calibrated for 245/65R17, an indicated 60 mph is actually 59.1 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 245/65R17.

Size pages

Other comparisons with 245/65R17

Other comparisons with 235/60R18

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