Tire Size Box

275/50R21 vs 275/55R21

275/55R21 compared with 275/50R21

+3.4% diameter, 0.0" width

275/55R21 is 32.91" tall vs 31.83". More than the 3% rule of thumb, so check carefully before switching.

31.8"21" rim5.4"10.8" wide
275/50R21 (solid) compared with 275/55R21 (dashed outline), drawn to scale

With 275/55R21 tires, when your speedometer says 60 mph you are really going

62.0 mph

275/55R21 is +1.08 inches (+3.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/50R21275/55R21Difference%
Overall diameter31.83"32.91"+1.08"+3.4%
Section width10.83"10.83"0.00"0.0%
Sidewall height5.41"5.95"+0.54"+10.0%
Circumference99.99"103.39"+3.40"+3.4%
Revolutions per mile633.7612.8−20.8−3.3%

Speedometer difference

If your vehicle came with 275/50R21 and you fit 275/55R21, 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 mph62.0 mph+2.0 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 275/50R21 or 275/55R21?
275/55R21 is taller by 1.08 inches (32.91" vs 31.83"). 275/50R21 is the same width.
Can I replace 275/50R21 with 275/55R21?
It is not recommended without checking carefully. The diameter difference is +3.4%, 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 275/55R21 change my speedometer?
When your speedometer reads 60 mph with 275/55R21 fitted (calibrated for 275/50R21), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.4%.
Will 275/55R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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