Tire Size Box

315/35R17 vs 315/45R17

315/45R17 compared with 315/35R17

+9.7% diameter, 0.0" width

315/45R17 is 28.16" tall vs 25.68". More than the 3% rule of thumb, so check carefully before switching.

25.7"17" rim4.3"12.4" wide
315/35R17 (solid) compared with 315/45R17 (dashed outline), drawn to scale

With 315/45R17 tires, when your speedometer says 60 mph you are really going

65.8 mph

315/45R17 is +2.48 inches (+9.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/35R17315/45R17Difference%
Overall diameter25.68"28.16"+2.48"+9.7%
Section width12.40"12.40"0.00"0.0%
Sidewall height4.34"5.58"+1.24"+28.6%
Circumference80.68"88.47"+7.79"+9.7%
Revolutions per mile785.3716.2−69.2−8.8%

Speedometer difference

If your vehicle came with 315/35R17 and you fit 315/45R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.9 mph+1.9 mph
30 mph32.9 mph+2.9 mph
40 mph43.9 mph+3.9 mph
50 mph54.8 mph+4.8 mph
60 mph65.8 mph+5.8 mph
65 mph71.3 mph+6.3 mph
70 mph76.8 mph+6.8 mph
75 mph82.2 mph+7.2 mph
80 mph87.7 mph+7.7 mph

Each size on its own

Questions

Which is bigger, 315/35R17 or 315/45R17?
315/45R17 is taller by 2.48 inches (28.16" vs 25.68"). 315/35R17 is the same width.
Can I replace 315/35R17 with 315/45R17?
It is not recommended without checking carefully. The diameter difference is +9.7%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 315/45R17 change my speedometer?
When your speedometer reads 60 mph with 315/45R17 fitted (calibrated for 315/35R17), your real speed is 65.8 mph. Your odometer will under-count miles by about 9.7%.
Will 315/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

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