195/65R15 vs 245/40R17

245/40R17 is 0.26 in (6.7 mm) shorter than 195/65R15, a −1.06% diameter difference. With the speedometer set for 195/65R15, an indicated 60 mph is 59.4 mph on 245/40R17.

Is this a safe swap?

Diameter difference −1.06%: within the ±3% guideline

By overall diameter alone, 245/40R17 falls inside the ±3% range commonly used as a guideline when replacing 195/65R15. 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.

195/65R15 vs 245/40R17 differences
Measurement	195/65R15	245/40R17	Difference	% diff
Overall diameter	24.98 in (634.5 mm)	24.72 in (627.8 mm)	−0.26 in (−6.7 mm)	−1.06%
Sidewall height	4.99 in (126.8 mm)	3.86 in (98.0 mm)	−1.13 in (−28.7 mm)	−22.68%
Section width	7.68 in (195.0 mm)	9.65 in (245.0 mm)	+1.97 in (+50.0 mm)	+25.64%
Circumference	78.48 in (1,993.3 mm)	77.65 in (1,972.3 mm)	−0.83 in (−21.0 mm)	−1.06%
Revolutions per mile	807	816	+9	+1.07%

True speed with the speedometer calibrated for 195/65R15
Indicated	Actual on 195/65R15	Actual on 245/40R17	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.4 mph	−0.6 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 245/40R17 lowers the vehicle by 0.13 in (3.4 mm) at the axle (half the −6.7 mm diameter difference).

245/40R17 is 0.26 in shorter than 195/65R15 and 50 mm wider, a 1.06% difference in overall diameter.

With the speedometer calibrated for 195/65R15, an indicated 60 mph is actually 59.4 mph on 245/40R17, and revolutions per mile change from 807 to 816.

245/40R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 195/65R15.

Size pages

Other comparisons with 195/65R15

Other comparisons with 245/40R17

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