Tire Size Box

265/50R18 vs 265/55R18

265/55R18 compared with 265/50R18

+3.7% diameter, 0.0" width

265/55R18 is 29.48" tall vs 28.43". More than the 3% rule of thumb, so check carefully before switching.

28.4"18" rim5.2"10.4" wide
265/50R18 (solid) compared with 265/55R18 (dashed outline), drawn to scale

With 265/55R18 tires, when your speedometer says 60 mph you are really going

62.2 mph

265/55R18 is +1.04 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

265/50R18265/55R18Difference%
Overall diameter28.43"29.48"+1.04"+3.7%
Section width10.43"10.43"0.00"0.0%
Sidewall height5.22"5.74"+0.52"+10.0%
Circumference89.33"92.60"+3.28"+3.7%
Revolutions per mile709.3684.2−25.1−3.5%

Speedometer difference

If your vehicle came with 265/50R18 and you fit 265/55R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 265/50R18 or 265/55R18?
265/55R18 is taller by 1.04 inches (29.48" vs 28.43"). 265/50R18 is the same width.
Can I replace 265/50R18 with 265/55R18?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 265/55R18 change my speedometer?
When your speedometer reads 60 mph with 265/55R18 fitted (calibrated for 265/50R18), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 265/55R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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