Tire Size Box

235/50R20 vs 235/55R20

235/55R20 compared with 235/50R20

+3.2% diameter, 0.0" width

235/55R20 is 30.18" tall vs 29.25". More than the 3% rule of thumb, so check carefully before switching.

29.3"20" rim4.6"9.3" wide
235/50R20 (solid) compared with 235/55R20 (dashed outline), drawn to scale

With 235/55R20 tires, when your speedometer says 60 mph you are really going

61.9 mph

235/55R20 is +0.93 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/50R20235/55R20Difference%
Overall diameter29.25"30.18"+0.93"+3.2%
Section width9.25"9.25"0.00"0.0%
Sidewall height4.63"5.09"+0.46"+10.0%
Circumference91.90"94.80"+2.91"+3.2%
Revolutions per mile689.5668.3−21.1−3.1%

Speedometer difference

If your vehicle came with 235/50R20 and you fit 235/55R20, 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 mph67.1 mph+2.1 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, 235/50R20 or 235/55R20?
235/55R20 is taller by 0.93 inches (30.18" vs 29.25"). 235/50R20 is the same width.
Can I replace 235/50R20 with 235/55R20?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 235/55R20 change my speedometer?
When your speedometer reads 60 mph with 235/55R20 fitted (calibrated for 235/50R20), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 235/55R20 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

Other comparisons