Tire Size Box

315/55R20 vs 315/60R20

315/60R20 compared with 315/55R20

+3.7% diameter, 0.0" width

315/60R20 is 34.88" tall vs 33.64". More than the 3% rule of thumb, so check carefully before switching.

33.6"20" rim6.8"12.4" wide
315/55R20 (solid) compared with 315/60R20 (dashed outline), drawn to scale

With 315/60R20 tires, when your speedometer says 60 mph you are really going

62.2 mph

315/60R20 is +1.24 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/55R20315/60R20Difference%
Overall diameter33.64"34.88"+1.24"+3.7%
Section width12.40"12.40"0.00"0.0%
Sidewall height6.82"7.44"+0.62"+9.1%
Circumference105.69"109.58"+3.90"+3.7%
Revolutions per mile599.5578.2−21.3−3.6%

Speedometer difference

If your vehicle came with 315/55R20 and you fit 315/60R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 315/55R20 or 315/60R20?
315/60R20 is taller by 1.24 inches (34.88" vs 33.64"). 315/55R20 is the same width.
Can I replace 315/55R20 with 315/60R20?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 315/60R20 change my speedometer?
When your speedometer reads 60 mph with 315/60R20 fitted (calibrated for 315/55R20), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 315/60R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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