Tire Size Box

325/55R20 vs 325/60R20

325/60R20 compared with 325/55R20

+3.8% diameter, 0.0" width

325/60R20 is 35.35" tall vs 34.07". More than the 3% rule of thumb, so check carefully before switching.

34.1"20" rim7.0"12.8" wide
325/55R20 (solid) compared with 325/60R20 (dashed outline), drawn to scale

With 325/60R20 tires, when your speedometer says 60 mph you are really going

62.3 mph

325/60R20 is +1.28 inches (+3.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/55R20325/60R20Difference%
Overall diameter34.07"35.35"+1.28"+3.8%
Section width12.80"12.80"0.00"0.0%
Sidewall height7.04"7.68"+0.64"+9.1%
Circumference107.05"111.07"+4.02"+3.8%
Revolutions per mile591.9570.5−21.4−3.6%

Speedometer difference

If your vehicle came with 325/55R20 and you fit 325/60R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.3 mph+2.3 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 325/55R20 or 325/60R20?
325/60R20 is taller by 1.28 inches (35.35" vs 34.07"). 325/55R20 is the same width.
Can I replace 325/55R20 with 325/60R20?
It is not recommended without checking carefully. The diameter difference is +3.8%, 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 325/60R20 change my speedometer?
When your speedometer reads 60 mph with 325/60R20 fitted (calibrated for 325/55R20), your real speed is 62.3 mph. Your odometer will under-count miles by about 3.8%.
Will 325/60R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.64 inches of ground clearance at the axle.

Other comparisons