295/40R18 vs 215/55R18

215/55R18 is 0.02 in (0.5 mm) taller than 295/40R18, a +0.07% diameter difference. With the speedometer set for 295/40R18, an indicated 60 mph is 60.0 mph on 215/55R18.

Is this a safe swap?

Diameter difference +0.07%: under 1%

By overall diameter alone, 215/55R18 is a near match for 295/40R18; 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.

295/40R18 vs 215/55R18 differences
Measurement	295/40R18	215/55R18	Difference	% diff
Overall diameter	27.29 in (693.2 mm)	27.31 in (693.7 mm)	+0.02 in (+0.5 mm)	+0.07%
Sidewall height	4.65 in (118.0 mm)	4.66 in (118.3 mm)	+0.01 in (+0.3 mm)	+0.21%
Section width	11.61 in (295.0 mm)	8.46 in (215.0 mm)	−3.15 in (−80.0 mm)	−27.12%
Circumference	85.74 in (2,177.8 mm)	85.80 in (2,179.3 mm)	+0.06 in (+1.6 mm)	+0.07%
Revolutions per mile	739	738	−1	−0.07%

True speed with the speedometer calibrated for 295/40R18
Indicated	Actual on 295/40R18	Actual on 215/55R18	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	60.0 mph	0.0 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 215/55R18 raises the vehicle by 0.01 in (0.3 mm) at the axle (half the +0.5 mm diameter difference).

215/55R18 is 0.02 in taller than 295/40R18 and 80 mm narrower, a 0.07% difference in overall diameter.

With the speedometer calibrated for 295/40R18, an indicated 60 mph is actually 60.0 mph on 215/55R18, and revolutions per mile change from 739 to 738.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 295/40R18

Other comparisons with 215/55R18

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