Tire Size Box

255/55R20 vs 255/60R20

255/60R20 compared with 255/55R20

+3.2% diameter, 0.0" width

255/60R20 is 32.05" tall vs 31.04". More than the 3% rule of thumb, so check carefully before switching.

31.0"20" rim5.5"10.0" wide
255/55R20 (solid) compared with 255/60R20 (dashed outline), drawn to scale

With 255/60R20 tires, when your speedometer says 60 mph you are really going

61.9 mph

255/60R20 is +1.00 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/55R20255/60R20Difference%
Overall diameter31.04"32.05"+1.00"+3.2%
Section width10.04"10.04"0.00"0.0%
Sidewall height5.52"6.02"+0.50"+9.1%
Circumference97.53"100.68"+3.15"+3.2%
Revolutions per mile649.7629.3−20.4−3.1%

Speedometer difference

If your vehicle came with 255/55R20 and you fit 255/60R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.4 mph+2.4 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 255/55R20 or 255/60R20?
255/60R20 is taller by 1.00 inches (32.05" vs 31.04"). 255/55R20 is the same width.
Can I replace 255/55R20 with 255/60R20?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 255/60R20 change my speedometer?
When your speedometer reads 60 mph with 255/60R20 fitted (calibrated for 255/55R20), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 255/60R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.50 inches of ground clearance at the axle.

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