225/65R17 vs 265/50R18

265/50R18 is 0.08 in (2.1 mm) shorter than 225/65R17, a −0.29% diameter difference. With the speedometer set for 225/65R17, an indicated 60 mph is 59.8 mph on 265/50R18.

Is this a safe swap?

Diameter difference −0.29%: under 1%

By overall diameter alone, 265/50R18 is a near match for 225/65R17; 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.

225/65R17 vs 265/50R18 differences
Measurement	225/65R17	265/50R18	Difference	% diff
Overall diameter	28.52 in (724.3 mm)	28.43 in (722.2 mm)	−0.08 in (−2.1 mm)	−0.29%
Sidewall height	5.76 in (146.3 mm)	5.22 in (132.5 mm)	−0.54 in (−13.7 mm)	−9.40%
Section width	8.86 in (225.0 mm)	10.43 in (265.0 mm)	+1.57 in (+40.0 mm)	+17.78%
Circumference	89.58 in (2,275.5 mm)	89.33 in (2,268.9 mm)	−0.26 in (−6.6 mm)	−0.29%
Revolutions per mile	707	709	+2	+0.29%

True speed with the speedometer calibrated for 225/65R17
Indicated	Actual on 225/65R17	Actual on 265/50R18	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 265/50R18 lowers the vehicle by 0.04 in (1.0 mm) at the axle (half the −2.1 mm diameter difference).

265/50R18 is 0.08 in shorter than 225/65R17 and 40 mm wider, a 0.29% difference in overall diameter.

With the speedometer calibrated for 225/65R17, an indicated 60 mph is actually 59.8 mph on 265/50R18, and revolutions per mile change from 707 to 709.

265/50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 225/65R17.

Size pages

Other comparisons with 225/65R17

Other comparisons with 265/50R18

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