205/50R17 vs 265/35R18

265/35R18 is 0.23 in (5.9 mm) taller than 205/50R17, a +0.93% diameter difference. With the speedometer set for 205/50R17, an indicated 60 mph is 60.6 mph on 265/35R18.

Is this a safe swap?

Diameter difference +0.93%: under 1%

By overall diameter alone, 265/35R18 is a near match for 205/50R17; 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.

205/50R17 vs 265/35R18 differences
Measurement	205/50R17	265/35R18	Difference	% diff
Overall diameter	25.07 in (636.8 mm)	25.30 in (642.7 mm)	+0.23 in (+5.9 mm)	+0.93%
Sidewall height	4.04 in (102.5 mm)	3.65 in (92.8 mm)	−0.38 in (−9.7 mm)	−9.51%
Section width	8.07 in (205.0 mm)	10.43 in (265.0 mm)	+2.36 in (+60.0 mm)	+29.27%
Circumference	78.76 in (2,000.6 mm)	79.49 in (2,019.1 mm)	+0.73 in (+18.5 mm)	+0.93%
Revolutions per mile	804	797	−7	−0.92%

True speed with the speedometer calibrated for 205/50R17
Indicated	Actual on 205/50R17	Actual on 265/35R18	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.7 mph	+0.7 mph

Ride-height change: 265/35R18 raises the vehicle by 0.12 in (3.0 mm) at the axle (half the +5.9 mm diameter difference).

265/35R18 is 0.23 in taller than 205/50R17 and 60 mm wider, a 0.93% difference in overall diameter.

With the speedometer calibrated for 205/50R17, an indicated 60 mph is actually 60.6 mph on 265/35R18, and revolutions per mile change from 804 to 797.

265/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 205/50R17.

Size pages

Other comparisons with 205/50R17

Other comparisons with 265/35R18

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