Tire Size Box

255/60R20 vs 255/65R20

255/65R20 compared with 255/60R20

+3.1% diameter, 0.0" width

255/65R20 is 33.05" tall vs 32.05". More than the 3% rule of thumb, so check carefully before switching.

32.0"20" rim6.0"10.0" wide
255/60R20 (solid) compared with 255/65R20 (dashed outline), drawn to scale

With 255/65R20 tires, when your speedometer says 60 mph you are really going

61.9 mph

255/65R20 is +1.00 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/60R20255/65R20Difference%
Overall diameter32.05"33.05"+1.00"+3.1%
Section width10.04"10.04"0.00"0.0%
Sidewall height6.02"6.53"+0.50"+8.3%
Circumference100.68"103.83"+3.15"+3.1%
Revolutions per mile629.3610.2−19.1−3.0%

Speedometer difference

If your vehicle came with 255/60R20 and you fit 255/65R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.0 mph+2.0 mph
70 mph72.2 mph+2.2 mph
75 mph77.3 mph+2.3 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 255/60R20 or 255/65R20?
255/65R20 is taller by 1.00 inches (33.05" vs 32.05"). 255/60R20 is the same width.
Can I replace 255/60R20 with 255/65R20?
It is not recommended without checking carefully. The diameter difference is +3.1%, 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 255/65R20 change my speedometer?
When your speedometer reads 60 mph with 255/65R20 fitted (calibrated for 255/60R20), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 255/65R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.50 inches of ground clearance at the axle.

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