Tire Size Box

315/55R17 vs 315/65R17

315/65R17 compared with 315/55R17

+8.1% diameter, 0.0" width

315/65R17 is 33.12" tall vs 30.64". More than the 3% rule of thumb, so check carefully before switching.

30.6"17" rim6.8"12.4" wide
315/55R17 (solid) compared with 315/65R17 (dashed outline), drawn to scale

With 315/65R17 tires, when your speedometer says 60 mph you are really going

64.9 mph

315/65R17 is +2.48 inches (+8.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/55R17315/65R17Difference%
Overall diameter30.64"33.12"+2.48"+8.1%
Section width12.40"12.40"0.00"0.0%
Sidewall height6.82"8.06"+1.24"+18.2%
Circumference96.26"104.06"+7.79"+8.1%
Revolutions per mile658.2608.9−49.3−7.5%

Speedometer difference

If your vehicle came with 315/55R17 and you fit 315/65R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.4 mph+2.4 mph
40 mph43.2 mph+3.2 mph
50 mph54.0 mph+4.0 mph
60 mph64.9 mph+4.9 mph
65 mph70.3 mph+5.3 mph
70 mph75.7 mph+5.7 mph
75 mph81.1 mph+6.1 mph
80 mph86.5 mph+6.5 mph

Each size on its own

Questions

Which is bigger, 315/55R17 or 315/65R17?
315/65R17 is taller by 2.48 inches (33.12" vs 30.64"). 315/55R17 is the same width.
Can I replace 315/55R17 with 315/65R17?
It is not recommended without checking carefully. The diameter difference is +8.1%, 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 315/65R17 change my speedometer?
When your speedometer reads 60 mph with 315/65R17 fitted (calibrated for 315/55R17), your real speed is 64.9 mph. Your odometer will under-count miles by about 8.1%.
Will 315/65R17 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

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