215/45R17 vs 245/40R17

245/40R17 is 0.10 in (2.5 mm) taller than 215/45R17, a +0.40% diameter difference. With the speedometer set for 215/45R17, an indicated 60 mph is 60.2 mph on 245/40R17.

Is this a safe swap?

Diameter difference +0.40%: under 1%

By overall diameter alone, 245/40R17 is a near match for 215/45R17; 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.

215/45R17 vs 245/40R17 differences
Measurement	215/45R17	245/40R17	Difference	% diff
Overall diameter	24.62 in (625.3 mm)	24.72 in (627.8 mm)	+0.10 in (+2.5 mm)	+0.40%
Sidewall height	3.81 in (96.8 mm)	3.86 in (98.0 mm)	+0.05 in (+1.3 mm)	+1.29%
Section width	8.46 in (215.0 mm)	9.65 in (245.0 mm)	+1.18 in (+30.0 mm)	+13.95%
Circumference	77.34 in (1,964.4 mm)	77.65 in (1,972.3 mm)	+0.31 in (+7.9 mm)	+0.40%
Revolutions per mile	819	816	−3	−0.40%

True speed with the speedometer calibrated for 215/45R17
Indicated	Actual on 215/45R17	Actual on 245/40R17	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	75.3 mph	+0.3 mph

Ride-height change: 245/40R17 raises the vehicle by 0.05 in (1.3 mm) at the axle (half the +2.5 mm diameter difference).

245/40R17 is 0.10 in taller than 215/45R17 and 30 mm wider, a 0.40% difference in overall diameter.

With the speedometer calibrated for 215/45R17, an indicated 60 mph is actually 60.2 mph on 245/40R17, and revolutions per mile change from 819 to 816.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 215/45R17

Other comparisons with 245/40R17

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