235/75R17 vs 275/60R18

275/60R18 is 0.11 in (2.9 mm) taller than 235/75R17, a +0.37% diameter difference. With the speedometer set for 235/75R17, an indicated 60 mph is 60.2 mph on 275/60R18.

Is this a safe swap?

Diameter difference +0.37%: under 1%

By overall diameter alone, 275/60R18 is a near match for 235/75R17; the speedometer changes by less than 1%. 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.

235/75R17 vs 275/60R18 differences
Measurement	235/75R17	275/60R18	Difference	% diff
Overall diameter	30.88 in (784.3 mm)	30.99 in (787.2 mm)	+0.11 in (+2.9 mm)	+0.37%
Sidewall height	6.94 in (176.3 mm)	6.50 in (165.0 mm)	−0.44 in (−11.2 mm)	−6.38%
Section width	9.25 in (235.0 mm)	10.83 in (275.0 mm)	+1.57 in (+40.0 mm)	+17.02%
Circumference	97.01 in (2,464.0 mm)	97.36 in (2,473.1 mm)	+0.36 in (+9.1 mm)	+0.37%
Revolutions per mile	653	651	−2	−0.37%

True speed with the speedometer calibrated for 235/75R17
Indicated	Actual on 235/75R17	Actual on 275/60R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.3 mph	+0.3 mph

Ride-height change: 275/60R18 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +2.9 mm diameter difference).

275/60R18 is 0.11 in taller than 235/75R17 and 40 mm wider, a 0.37% difference in overall diameter.

With the speedometer calibrated for 235/75R17, an indicated 60 mph is actually 60.2 mph on 275/60R18, and revolutions per mile change from 653 to 651.

275/60R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 235/75R17.

Size pages

Other comparisons with 235/75R17

Other comparisons with 275/60R18

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