Tire Size Box

255/55R18 vs 255/60R18

255/60R18 compared with 255/55R18

+3.5% diameter, 0.0" width

255/60R18 is 30.05" tall vs 29.04". More than the 3% rule of thumb, so check carefully before switching.

29.0"18" rim5.5"10.0" wide
255/55R18 (solid) compared with 255/60R18 (dashed outline), drawn to scale

With 255/60R18 tires, when your speedometer says 60 mph you are really going

62.1 mph

255/60R18 is +1.00 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/55R18255/60R18Difference%
Overall diameter29.04"30.05"+1.00"+3.5%
Section width10.04"10.04"0.00"0.0%
Sidewall height5.52"6.02"+0.50"+9.1%
Circumference91.24"94.40"+3.15"+3.5%
Revolutions per mile694.4671.2−23.2−3.3%

Speedometer difference

If your vehicle came with 255/55R18 and you fit 255/60R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.4 mph+1.4 mph
50 mph51.7 mph+1.7 mph
60 mph62.1 mph+2.1 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 255/55R18 or 255/60R18?
255/60R18 is taller by 1.00 inches (30.05" vs 29.04"). 255/55R18 is the same width.
Can I replace 255/55R18 with 255/60R18?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 255/60R18 change my speedometer?
When your speedometer reads 60 mph with 255/60R18 fitted (calibrated for 255/55R18), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 255/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.50 inches of ground clearance at the axle.

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