Tire Size Box

315/55R18 vs 315/60R18

315/60R18 compared with 315/55R18

+3.9% diameter, 0.0" width

315/60R18 is 32.88" tall vs 31.64". More than the 3% rule of thumb, so check carefully before switching.

31.6"18" rim6.8"12.4" wide
315/55R18 (solid) compared with 315/60R18 (dashed outline), drawn to scale

With 315/60R18 tires, when your speedometer says 60 mph you are really going

62.4 mph

315/60R18 is +1.24 inches (+3.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/55R18315/60R18Difference%
Overall diameter31.64"32.88"+1.24"+3.9%
Section width12.40"12.40"0.00"0.0%
Sidewall height6.82"7.44"+0.62"+9.1%
Circumference99.41"103.30"+3.90"+3.9%
Revolutions per mile637.4613.4−24.0−3.8%

Speedometer difference

If your vehicle came with 315/55R18 and you fit 315/60R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.5 mph+2.5 mph
70 mph72.7 mph+2.7 mph
75 mph77.9 mph+2.9 mph
80 mph83.1 mph+3.1 mph

Each size on its own

Questions

Which is bigger, 315/55R18 or 315/60R18?
315/60R18 is taller by 1.24 inches (32.88" vs 31.64"). 315/55R18 is the same width.
Can I replace 315/55R18 with 315/60R18?
It is not recommended without checking carefully. The diameter difference is +3.9%, 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 315/60R18 change my speedometer?
When your speedometer reads 60 mph with 315/60R18 fitted (calibrated for 315/55R18), your real speed is 62.4 mph. Your odometer will under-count miles by about 3.9%.
Will 315/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.62 inches of ground clearance at the axle.

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