Tire Size Box

325/50R18 vs 325/60R18

325/60R18 compared with 325/50R18

+8.3% diameter, 0.0" width

325/60R18 is 33.35" tall vs 30.80". More than the 3% rule of thumb, so check carefully before switching.

30.8"18" rim6.4"12.8" wide
325/50R18 (solid) compared with 325/60R18 (dashed outline), drawn to scale

With 325/60R18 tires, when your speedometer says 60 mph you are really going

65.0 mph

325/60R18 is +2.56 inches (+8.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/50R18325/60R18Difference%
Overall diameter30.80"33.35"+2.56"+8.3%
Section width12.80"12.80"0.00"0.0%
Sidewall height6.40"7.68"+1.28"+20.0%
Circumference96.75"104.79"+8.04"+8.3%
Revolutions per mile654.9604.7−50.2−7.7%

Speedometer difference

If your vehicle came with 325/50R18 and you fit 325/60R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.7 mph+1.7 mph
30 mph32.5 mph+2.5 mph
40 mph43.3 mph+3.3 mph
50 mph54.2 mph+4.2 mph
60 mph65.0 mph+5.0 mph
65 mph70.4 mph+5.4 mph
70 mph75.8 mph+5.8 mph
75 mph81.2 mph+6.2 mph
80 mph86.6 mph+6.6 mph

Each size on its own

Questions

Which is bigger, 325/50R18 or 325/60R18?
325/60R18 is taller by 2.56 inches (33.35" vs 30.80"). 325/50R18 is the same width.
Can I replace 325/50R18 with 325/60R18?
It is not recommended without checking carefully. The diameter difference is +8.3%, 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 325/60R18 change my speedometer?
When your speedometer reads 60 mph with 325/60R18 fitted (calibrated for 325/50R18), your real speed is 65.0 mph. Your odometer will under-count miles by about 8.3%.
Will 325/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.28 inches of ground clearance at the axle.

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