Tire Size Box

255/50R15 vs 275/50R15

275/50R15 compared with 255/50R15

+3.1% diameter, +0.8" width

275/50R15 is 25.83" tall vs 25.04". More than the 3% rule of thumb, so check carefully before switching.

25.0"15" rim5.0"10.0" wide
255/50R15 (solid) compared with 275/50R15 (dashed outline), drawn to scale

With 275/50R15 tires, when your speedometer says 60 mph you are really going

61.9 mph

275/50R15 is +0.79 inches (+3.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/50R15275/50R15Difference%
Overall diameter25.04"25.83"+0.79"+3.1%
Section width10.04"10.83"+0.79"+7.8%
Sidewall height5.02"5.41"+0.39"+7.8%
Circumference78.66"81.14"+2.47"+3.1%
Revolutions per mile805.5780.9−24.6−3.0%

Speedometer difference

If your vehicle came with 255/50R15 and you fit 275/50R15, 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, 255/50R15 or 275/50R15?
275/50R15 is taller by 0.79 inches (25.83" vs 25.04"). 275/50R15 is wider by 0.79 inches.
Can I replace 255/50R15 with 275/50R15?
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 275/50R15 change my speedometer?
When your speedometer reads 60 mph with 275/50R15 fitted (calibrated for 255/50R15), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.1%.
Will 275/50R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.39 inches of ground clearance at the axle.

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