225/70R16 vs 265/50R18

265/50R18 is 0.03 in (0.8 mm) taller than 225/70R16, a +0.11% diameter difference. With the speedometer set for 225/70R16, an indicated 60 mph is 60.1 mph on 265/50R18.

Is this a safe swap?

Diameter difference +0.11%: under 1%

By overall diameter alone, 265/50R18 is a near match for 225/70R16; 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.

225/70R16 vs 265/50R18 differences
Measurement	225/70R16	265/50R18	Difference	% diff
Overall diameter	28.40 in (721.4 mm)	28.43 in (722.2 mm)	+0.03 in (+0.8 mm)	+0.11%
Sidewall height	6.20 in (157.5 mm)	5.22 in (132.5 mm)	−0.98 in (−25.0 mm)	−15.87%
Section width	8.86 in (225.0 mm)	10.43 in (265.0 mm)	+1.57 in (+40.0 mm)	+17.78%
Circumference	89.23 in (2,266.3 mm)	89.33 in (2,268.9 mm)	+0.10 in (+2.5 mm)	+0.11%
Revolutions per mile	710	709	−1	−0.11%

True speed with the speedometer calibrated for 225/70R16
Indicated	Actual on 225/70R16	Actual on 265/50R18	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	60.1 mph	+0.1 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 265/50R18 raises the vehicle by 0.02 in (0.4 mm) at the axle (half the +0.8 mm diameter difference).

265/50R18 is 0.03 in taller than 225/70R16 and 40 mm wider, a 0.11% difference in overall diameter.

With the speedometer calibrated for 225/70R16, an indicated 60 mph is actually 60.1 mph on 265/50R18, and revolutions per mile change from 710 to 709.

265/50R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/70R16.

Size pages

Other comparisons with 225/70R16

Other comparisons with 265/50R18

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