Tire Size Box

285/50R21 vs 285/55R21

285/55R21 compared with 285/50R21

+3.5% diameter, 0.0" width

285/55R21 is 33.34" tall vs 32.22". More than the 3% rule of thumb, so check carefully before switching.

32.2"21" rim5.6"11.2" wide
285/50R21 (solid) compared with 285/55R21 (dashed outline), drawn to scale

With 285/55R21 tires, when your speedometer says 60 mph you are really going

62.1 mph

285/55R21 is +1.12 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/50R21285/55R21Difference%
Overall diameter32.22"33.34"+1.12"+3.5%
Section width11.22"11.22"0.00"0.0%
Sidewall height5.61"6.17"+0.56"+10.0%
Circumference101.22"104.75"+3.53"+3.5%
Revolutions per mile625.9604.9−21.1−3.4%

Speedometer difference

If your vehicle came with 285/50R21 and you fit 285/55R21, 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 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 285/50R21 or 285/55R21?
285/55R21 is taller by 1.12 inches (33.34" vs 32.22"). 285/50R21 is the same width.
Can I replace 285/50R21 with 285/55R21?
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 285/55R21 change my speedometer?
When your speedometer reads 60 mph with 285/55R21 fitted (calibrated for 285/50R21), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 285/55R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.56 inches of ground clearance at the axle.

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