Tire Size Box

245/50R21 vs 245/55R21

245/55R21 compared with 245/50R21

+3.1% diameter, 0.0" width

245/55R21 is 31.61" tall vs 30.65". More than the 3% rule of thumb, so check carefully before switching.

30.6"21" rim4.8"9.6" wide
245/50R21 (solid) compared with 245/55R21 (dashed outline), drawn to scale

With 245/55R21 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/55R21 is +0.96 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/50R21245/55R21Difference%
Overall diameter30.65"31.61"+0.96"+3.1%
Section width9.65"9.65"0.00"0.0%
Sidewall height4.82"5.31"+0.48"+10.0%
Circumference96.28"99.31"+3.03"+3.1%
Revolutions per mile658.1638.0−20.1−3.1%

Speedometer difference

If your vehicle came with 245/50R21 and you fit 245/55R21, 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 mph77.4 mph+2.4 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 245/50R21 or 245/55R21?
245/55R21 is taller by 0.96 inches (31.61" vs 30.65"). 245/50R21 is the same width.
Can I replace 245/50R21 with 245/55R21?
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 245/55R21 change my speedometer?
When your speedometer reads 60 mph with 245/55R21 fitted (calibrated for 245/50R21), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 245/55R21 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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