205/45R17 vs 215/35R18

215/35R18 is 0.34 in (8.6 mm) shorter than 205/45R17, a −1.40% diameter difference. With the speedometer set for 205/45R17, an indicated 60 mph is 59.2 mph on 215/35R18.

Is this a safe swap?

Diameter difference −1.40%: within the ±3% guideline

By overall diameter alone, 215/35R18 falls inside the ±3% range commonly used as a guideline when replacing 205/45R17. 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.

205/45R17 vs 215/35R18 differences
Measurement	205/45R17	215/35R18	Difference	% diff
Overall diameter	24.26 in (616.3 mm)	23.93 in (607.7 mm)	−0.34 in (−8.6 mm)	−1.40%
Sidewall height	3.63 in (92.3 mm)	2.96 in (75.3 mm)	−0.67 in (−17.0 mm)	−18.43%
Section width	8.07 in (205.0 mm)	8.46 in (215.0 mm)	+0.39 in (+10.0 mm)	+4.88%
Circumference	76.23 in (1,936.2 mm)	75.16 in (1,909.1 mm)	−1.06 in (−27.0 mm)	−1.40%
Revolutions per mile	831	843	+12	+1.42%

True speed with the speedometer calibrated for 205/45R17
Indicated	Actual on 205/45R17	Actual on 215/35R18	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.2 mph	−0.8 mph
75 mph	75.0 mph	74.0 mph	−1.0 mph

Ride-height change: 215/35R18 lowers the vehicle by 0.17 in (4.3 mm) at the axle (half the −8.6 mm diameter difference).

215/35R18 is 0.34 in shorter than 205/45R17 and 10 mm wider, a 1.40% difference in overall diameter.

With the speedometer calibrated for 205/45R17, an indicated 60 mph is actually 59.2 mph on 215/35R18, and revolutions per mile change from 831 to 843.

215/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 205/45R17.

Size pages

Other comparisons with 205/45R17

Other comparisons with 215/35R18

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