Tire Size Box

315/50R18 vs 315/60R18

315/60R18 compared with 315/50R18

+8.2% diameter, 0.0" width

315/60R18 is 32.88" tall vs 30.40". More than the 3% rule of thumb, so check carefully before switching.

30.4"18" rim6.2"12.4" wide
315/50R18 (solid) compared with 315/60R18 (dashed outline), drawn to scale

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

64.9 mph

315/60R18 is +2.48 inches (+8.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

315/50R18315/60R18Difference%
Overall diameter30.40"32.88"+2.48"+8.2%
Section width12.40"12.40"0.00"0.0%
Sidewall height6.20"7.44"+1.24"+20.0%
Circumference95.51"103.30"+7.79"+8.2%
Revolutions per mile663.4613.4−50.0−7.5%

Speedometer difference

If your vehicle came with 315/50R18 and you fit 315/60R18, 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 mph43.3 mph+3.3 mph
50 mph54.1 mph+4.1 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, 315/50R18 or 315/60R18?
315/60R18 is taller by 2.48 inches (32.88" vs 30.40"). 315/50R18 is the same width.
Can I replace 315/50R18 with 315/60R18?
It is not recommended without checking carefully. The diameter difference is +8.2%, 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 315/50R18), your real speed is 64.9 mph. Your odometer will under-count miles by about 8.2%.
Will 315/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.24 inches of ground clearance at the axle.

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