Tire Size Box

315/45R17 vs 315/50R17

315/50R17 compared with 315/45R17

+4.4% diameter, 0.0" width

315/50R17 is 29.40" tall vs 28.16". More than the 3% rule of thumb, so check carefully before switching.

28.2"17" rim5.6"12.4" wide
315/45R17 (solid) compared with 315/50R17 (dashed outline), drawn to scale

With 315/50R17 tires, when your speedometer says 60 mph you are really going

62.6 mph

315/50R17 is +1.24 inches (+4.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/45R17315/50R17Difference%
Overall diameter28.16"29.40"+1.24"+4.4%
Section width12.40"12.40"0.00"0.0%
Sidewall height5.58"6.20"+0.62"+11.1%
Circumference88.47"92.37"+3.90"+4.4%
Revolutions per mile716.2686.0−30.2−4.2%

Speedometer difference

If your vehicle came with 315/45R17 and you fit 315/50R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.3 mph+1.3 mph
40 mph41.8 mph+1.8 mph
50 mph52.2 mph+2.2 mph
60 mph62.6 mph+2.6 mph
65 mph67.9 mph+2.9 mph
70 mph73.1 mph+3.1 mph
75 mph78.3 mph+3.3 mph
80 mph83.5 mph+3.5 mph

Each size on its own

Questions

Which is bigger, 315/45R17 or 315/50R17?
315/50R17 is taller by 1.24 inches (29.40" vs 28.16"). 315/45R17 is the same width.
Can I replace 315/45R17 with 315/50R17?
It is not recommended without checking carefully. The diameter difference is +4.4%, 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 315/50R17 change my speedometer?
When your speedometer reads 60 mph with 315/50R17 fitted (calibrated for 315/45R17), your real speed is 62.6 mph. Your odometer will under-count miles by about 4.4%.
Will 315/50R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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