215/55R18 vs 265/45R18

265/45R18 is 0.08 in (2.0 mm) taller than 215/55R18, a +0.29% diameter difference. With the speedometer set for 215/55R18, an indicated 60 mph is 60.2 mph on 265/45R18.

Is this a safe swap?

Diameter difference +0.29%: under 1%

By overall diameter alone, 265/45R18 is a near match for 215/55R18; 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.

215/55R18 vs 265/45R18 differences
Measurement	215/55R18	265/45R18	Difference	% diff
Overall diameter	27.31 in (693.7 mm)	27.39 in (695.7 mm)	+0.08 in (+2.0 mm)	+0.29%
Sidewall height	4.66 in (118.3 mm)	4.69 in (119.3 mm)	+0.04 in (+1.0 mm)	+0.85%
Section width	8.46 in (215.0 mm)	10.43 in (265.0 mm)	+1.97 in (+50.0 mm)	+23.26%
Circumference	85.80 in (2,179.3 mm)	86.05 in (2,185.6 mm)	+0.25 in (+6.3 mm)	+0.29%
Revolutions per mile	738	736	−2	−0.29%

True speed with the speedometer calibrated for 215/55R18
Indicated	Actual on 215/55R18	Actual on 265/45R18	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	75.2 mph	+0.2 mph

Ride-height change: 265/45R18 raises the vehicle by 0.04 in (1.0 mm) at the axle (half the +2.0 mm diameter difference).

265/45R18 is 0.08 in taller than 215/55R18 and 50 mm wider, a 0.29% difference in overall diameter.

With the speedometer calibrated for 215/55R18, an indicated 60 mph is actually 60.2 mph on 265/45R18, and revolutions per mile change from 738 to 736.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 215/55R18

Other comparisons with 265/45R18

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