Tire Size Box

255/80R15 vs 275/80R15

275/80R15 compared with 255/80R15

+4.1% diameter, +0.8" width

275/80R15 is 32.32" tall vs 31.06". More than the 3% rule of thumb, so check carefully before switching.

31.1"15" rim8.0"10.0" wide
255/80R15 (solid) compared with 275/80R15 (dashed outline), drawn to scale

With 275/80R15 tires, when your speedometer says 60 mph you are really going

62.4 mph

275/80R15 is +1.26 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/80R15275/80R15Difference%
Overall diameter31.06"32.32"+1.26"+4.1%
Section width10.04"10.83"+0.79"+7.8%
Sidewall height8.03"8.66"+0.63"+7.8%
Circumference97.59"101.55"+3.96"+4.1%
Revolutions per mile649.3624.0−25.3−3.9%

Speedometer difference

If your vehicle came with 255/80R15 and you fit 275/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 255/80R15 or 275/80R15?
275/80R15 is taller by 1.26 inches (32.32" vs 31.06"). 275/80R15 is wider by 0.79 inches.
Can I replace 255/80R15 with 275/80R15?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 275/80R15 change my speedometer?
When your speedometer reads 60 mph with 275/80R15 fitted (calibrated for 255/80R15), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.1%.
Will 275/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.63 inches of ground clearance at the axle.

Other comparisons