TireSizesFinder

275/40R17 vs 245/45R17

245/45R17 is 0.02 in (0.5 mm) taller than 275/40R17, a +0.08% diameter difference. With the speedometer set for 275/40R17, an indicated 60 mph is 60.0 mph on 245/45R17.

Is this a safe swap?

Diameter difference +0.08%: under 1%

By overall diameter alone, 245/45R17 is a near match for 275/40R17; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 275/40R17 (25.66 in) vs 245/45R17 (25.68 in)275/40R1725.66 in × 10.83 in245/45R1725.68 in × 9.65 in
Side profile and tread width, drawn to the same scale.
275/40R17 vs 245/45R17 differences
Measurement275/40R17245/45R17Difference% diff
Overall diameter25.66 in (651.8 mm)25.68 in (652.3 mm)+0.02 in (+0.5 mm)+0.08%
Sidewall height4.33 in (110.0 mm)4.34 in (110.3 mm)+0.01 in (+0.3 mm)+0.23%
Section width10.83 in (275.0 mm)9.65 in (245.0 mm)−1.18 in (−30.0 mm)−10.91%
Circumference80.62 in (2,047.7 mm)80.68 in (2,049.3 mm)+0.06 in (+1.6 mm)+0.08%
Revolutions per mile786785−1−0.08%
True speed with the speedometer calibrated for 275/40R17
IndicatedActual on 275/40R17Actual on 245/45R17Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.0 mph0.0 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 245/45R17 raises the vehicle by 0.01 in (0.3 mm) at the axle (half the +0.5 mm diameter difference).

245/45R17 is 0.02 in taller than 275/40R17 and 30 mm narrower, a 0.08% difference in overall diameter.

With the speedometer calibrated for 275/40R17, an indicated 60 mph is actually 60.0 mph on 245/45R17, and revolutions per mile change from 786 to 785.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 275/40R17

Other comparisons with 245/45R17

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.