Tire Size Box

255/60R15 vs 275/60R15

275/60R15 compared with 255/60R15

+3.5% diameter, +0.8" width

275/60R15 is 27.99" tall vs 27.05". More than the 3% rule of thumb, so check carefully before switching.

27.0"15" rim6.0"10.0" wide
255/60R15 (solid) compared with 275/60R15 (dashed outline), drawn to scale

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

62.1 mph

275/60R15 is +0.94 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/60R15275/60R15Difference%
Overall diameter27.05"27.99"+0.94"+3.5%
Section width10.04"10.83"+0.79"+7.8%
Sidewall height6.02"6.50"+0.47"+7.8%
Circumference84.97"87.94"+2.97"+3.5%
Revolutions per mile745.7720.5−25.2−3.4%

Speedometer difference

If your vehicle came with 255/60R15 and you fit 275/60R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.4 mph+1.4 mph
50 mph51.7 mph+1.7 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 255/60R15 or 275/60R15?
275/60R15 is taller by 0.94 inches (27.99" vs 27.05"). 275/60R15 is wider by 0.79 inches.
Can I replace 255/60R15 with 275/60R15?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 275/60R15 change my speedometer?
When your speedometer reads 60 mph with 275/60R15 fitted (calibrated for 255/60R15), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 275/60R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.47 inches of ground clearance at the axle.

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