Tire Size Box

255/65R15 vs 275/65R15

275/65R15 compared with 255/65R15

+3.6% diameter, +0.8" width

275/65R15 is 29.07" tall vs 28.05". More than the 3% rule of thumb, so check carefully before switching.

28.1"15" rim6.5"10.0" wide
255/65R15 (solid) compared with 275/65R15 (dashed outline), drawn to scale

With 275/65R15 tires, when your speedometer says 60 mph you are really going

62.2 mph

275/65R15 is +1.02 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/65R15275/65R15Difference%
Overall diameter28.05"29.07"+1.02"+3.6%
Section width10.04"10.83"+0.79"+7.8%
Sidewall height6.53"7.04"+0.51"+7.8%
Circumference88.13"91.34"+3.22"+3.6%
Revolutions per mile719.0693.7−25.3−3.5%

Speedometer difference

If your vehicle came with 255/65R15 and you fit 275/65R15, 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 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 255/65R15 or 275/65R15?
275/65R15 is taller by 1.02 inches (29.07" vs 28.05"). 275/65R15 is wider by 0.79 inches.
Can I replace 255/65R15 with 275/65R15?
It is not recommended without checking carefully. The diameter difference is +3.6%, 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 275/65R15 change my speedometer?
When your speedometer reads 60 mph with 275/65R15 fitted (calibrated for 255/65R15), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.6%.
Will 275/65R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.51 inches of ground clearance at the axle.

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