235/50R18 vs 265/45R18

265/45R18 is 0.14 in (3.5 mm) taller than 235/50R18, a +0.51% diameter difference. With the speedometer set for 235/50R18, an indicated 60 mph is 60.3 mph on 265/45R18.

Is this a safe swap?

Diameter difference +0.51%: under 1%

By overall diameter alone, 265/45R18 is a near match for 235/50R18; 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.

235/50R18 vs 265/45R18 differences
Measurement	235/50R18	265/45R18	Difference	% diff
Overall diameter	27.25 in (692.2 mm)	27.39 in (695.7 mm)	+0.14 in (+3.5 mm)	+0.51%
Sidewall height	4.63 in (117.5 mm)	4.69 in (119.3 mm)	+0.07 in (+1.8 mm)	+1.49%
Section width	9.25 in (235.0 mm)	10.43 in (265.0 mm)	+1.18 in (+30.0 mm)	+12.77%
Circumference	85.61 in (2,174.6 mm)	86.05 in (2,185.6 mm)	+0.43 in (+11.0 mm)	+0.51%
Revolutions per mile	740	736	−4	−0.50%

True speed with the speedometer calibrated for 235/50R18
Indicated	Actual on 235/50R18	Actual on 265/45R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 265/45R18 raises the vehicle by 0.07 in (1.8 mm) at the axle (half the +3.5 mm diameter difference).

265/45R18 is 0.14 in taller than 235/50R18 and 30 mm wider, a 0.51% difference in overall diameter.

With the speedometer calibrated for 235/50R18, an indicated 60 mph is actually 60.3 mph on 265/45R18, and revolutions per mile change from 740 to 736.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 235/50R18

Other comparisons with 265/45R18

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