265/40R17 vs 275/35R18

275/35R18 is 0.23 in (5.9 mm) taller than 265/40R17, a +0.92% diameter difference. With the speedometer set for 265/40R17, an indicated 60 mph is 60.5 mph on 275/35R18.

Is this a safe swap?

Diameter difference +0.92%: under 1%

By overall diameter alone, 275/35R18 is a near match for 265/40R17; 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.

265/40R17 vs 275/35R18 differences
Measurement	265/40R17	275/35R18	Difference	% diff
Overall diameter	25.35 in (643.8 mm)	25.58 in (649.7 mm)	+0.23 in (+5.9 mm)	+0.92%
Sidewall height	4.17 in (106.0 mm)	3.79 in (96.3 mm)	−0.38 in (−9.7 mm)	−9.20%
Section width	10.43 in (265.0 mm)	10.83 in (275.0 mm)	+0.39 in (+10.0 mm)	+3.77%
Circumference	79.63 in (2,022.6 mm)	80.36 in (2,041.1 mm)	+0.73 in (+18.5 mm)	+0.92%
Revolutions per mile	796	788	−7	−0.91%

True speed with the speedometer calibrated for 265/40R17
Indicated	Actual on 265/40R17	Actual on 275/35R18	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.7 mph	+0.7 mph

Ride-height change: 275/35R18 raises the vehicle by 0.12 in (3.0 mm) at the axle (half the +5.9 mm diameter difference).

275/35R18 is 0.23 in taller than 265/40R17 and 10 mm wider, a 0.92% difference in overall diameter.

With the speedometer calibrated for 265/40R17, an indicated 60 mph is actually 60.5 mph on 275/35R18, and revolutions per mile change from 796 to 788.

275/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 265/40R17.

Size pages

Other comparisons with 265/40R17

Other comparisons with 275/35R18

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