215/60R16 vs 235/45R18

235/45R18 is 0.17 in (4.3 mm) taller than 215/60R16, a +0.65% diameter difference. With the speedometer set for 215/60R16, an indicated 60 mph is 60.4 mph on 235/45R18.

Is this a safe swap?

Diameter difference +0.65%: under 1%

By overall diameter alone, 235/45R18 is a near match for 215/60R16; 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.

215/60R16 vs 235/45R18 differences
Measurement	215/60R16	235/45R18	Difference	% diff
Overall diameter	26.16 in (664.4 mm)	26.33 in (668.7 mm)	+0.17 in (+4.3 mm)	+0.65%
Sidewall height	5.08 in (129.0 mm)	4.16 in (105.8 mm)	−0.92 in (−23.2 mm)	−18.02%
Section width	8.46 in (215.0 mm)	9.25 in (235.0 mm)	+0.79 in (+20.0 mm)	+9.30%
Circumference	82.18 in (2,087.3 mm)	82.71 in (2,100.8 mm)	+0.53 in (+13.5 mm)	+0.65%
Revolutions per mile	771	766	−5	−0.64%

True speed with the speedometer calibrated for 215/60R16
Indicated	Actual on 215/60R16	Actual on 235/45R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 235/45R18 raises the vehicle by 0.08 in (2.2 mm) at the axle (half the +4.3 mm diameter difference).

235/45R18 is 0.17 in taller than 215/60R16 and 20 mm wider, a 0.65% difference in overall diameter.

With the speedometer calibrated for 215/60R16, an indicated 60 mph is actually 60.4 mph on 235/45R18, and revolutions per mile change from 771 to 766.

235/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/60R16.

Size pages

Other comparisons with 215/60R16

Other comparisons with 235/45R18

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