195/70R15 vs 245/45R17

245/45R17 is 0.07 in (1.7 mm) shorter than 195/70R15, a −0.26% diameter difference. With the speedometer set for 195/70R15, an indicated 60 mph is 59.8 mph on 245/45R17.

Is this a safe swap?

Diameter difference −0.26%: under 1%

By overall diameter alone, 245/45R17 is a near match for 195/70R15; 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.

195/70R15 vs 245/45R17 differences
Measurement	195/70R15	245/45R17	Difference	% diff
Overall diameter	25.75 in (654.0 mm)	25.68 in (652.3 mm)	−0.07 in (−1.7 mm)	−0.26%
Sidewall height	5.37 in (136.5 mm)	4.34 in (110.3 mm)	−1.03 in (−26.2 mm)	−19.23%
Section width	7.68 in (195.0 mm)	9.65 in (245.0 mm)	+1.97 in (+50.0 mm)	+25.64%
Circumference	80.89 in (2,054.6 mm)	80.68 in (2,049.3 mm)	−0.21 in (−5.3 mm)	−0.26%
Revolutions per mile	783	785	+2	+0.26%

True speed with the speedometer calibrated for 195/70R15
Indicated	Actual on 195/70R15	Actual on 245/45R17	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 245/45R17 lowers the vehicle by 0.03 in (0.9 mm) at the axle (half the −1.7 mm diameter difference).

245/45R17 is 0.07 in shorter than 195/70R15 and 50 mm wider, a 0.26% difference in overall diameter.

With the speedometer calibrated for 195/70R15, an indicated 60 mph is actually 59.8 mph on 245/45R17, and revolutions per mile change from 783 to 785.

245/45R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 195/70R15.

Size pages

Other comparisons with 195/70R15

Other comparisons with 245/45R17

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