Tire Size Box

275/50R20 vs 275/55R20

275/55R20 compared with 275/50R20

+3.5% diameter, 0.0" width

275/55R20 is 31.91" tall vs 30.83". More than the 3% rule of thumb, so check carefully before switching.

30.8"20" rim5.4"10.8" wide
275/50R20 (solid) compared with 275/55R20 (dashed outline), drawn to scale

With 275/55R20 tires, when your speedometer says 60 mph you are really going

62.1 mph

275/55R20 is +1.08 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/50R20275/55R20Difference%
Overall diameter30.83"31.91"+1.08"+3.5%
Section width10.83"10.83"0.00"0.0%
Sidewall height5.41"5.95"+0.54"+10.0%
Circumference96.85"100.25"+3.40"+3.5%
Revolutions per mile654.2632.0−22.2−3.4%

Speedometer difference

If your vehicle came with 275/50R20 and you fit 275/55R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 275/50R20 or 275/55R20?
275/55R20 is taller by 1.08 inches (31.91" vs 30.83"). 275/50R20 is the same width.
Can I replace 275/50R20 with 275/55R20?
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 275/55R20 change my speedometer?
When your speedometer reads 60 mph with 275/55R20 fitted (calibrated for 275/50R20), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 275/55R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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