Tire Size Box

215/50R18 vs 215/55R18

215/55R18 compared with 215/50R18

+3.2% diameter, 0.0" width

215/55R18 is 27.31" tall vs 26.46". More than the 3% rule of thumb, so check carefully before switching.

26.5"18" rim4.2"8.5" wide
215/50R18 (solid) compared with 215/55R18 (dashed outline), drawn to scale

With 215/55R18 tires, when your speedometer says 60 mph you are really going

61.9 mph

215/55R18 is +0.85 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

215/50R18215/55R18Difference%
Overall diameter26.46"27.31"+0.85"+3.2%
Section width8.46"8.46"0.00"0.0%
Sidewall height4.23"4.66"+0.42"+10.0%
Circumference83.14"85.80"+2.66"+3.2%
Revolutions per mile762.1738.5−23.6−3.1%

Speedometer difference

If your vehicle came with 215/50R18 and you fit 215/55R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 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 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 215/50R18 or 215/55R18?
215/55R18 is taller by 0.85 inches (27.31" vs 26.46"). 215/50R18 is the same width.
Can I replace 215/50R18 with 215/55R18?
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 215/55R18 change my speedometer?
When your speedometer reads 60 mph with 215/55R18 fitted (calibrated for 215/50R18), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 215/55R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.42 inches of ground clearance at the axle.

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