Tire Size Box

255/70R17 vs 275/70R17

275/70R17 compared with 255/70R17

+3.5% diameter, +0.8" width

275/70R17 is 32.16" tall vs 31.06". More than the 3% rule of thumb, so check carefully before switching.

31.1"17" rim7.0"10.0" wide
255/70R17 (solid) compared with 275/70R17 (dashed outline), drawn to scale

With 275/70R17 tires, when your speedometer says 60 mph you are really going

62.1 mph

275/70R17 is +1.10 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

255/70R17275/70R17Difference%
Overall diameter31.06"32.16"+1.10"+3.5%
Section width10.04"10.83"+0.79"+7.8%
Sidewall height7.03"7.58"+0.55"+7.8%
Circumference97.56"101.03"+3.46"+3.5%
Revolutions per mile649.4627.2−22.3−3.4%

Speedometer difference

If your vehicle came with 255/70R17 and you fit 275/70R17, 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 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.7 mph+2.7 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 255/70R17 or 275/70R17?
275/70R17 is taller by 1.10 inches (32.16" vs 31.06"). 275/70R17 is wider by 0.79 inches.
Can I replace 255/70R17 with 275/70R17?
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 275/70R17 change my speedometer?
When your speedometer reads 60 mph with 275/70R17 fitted (calibrated for 255/70R17), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 275/70R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.55 inches of ground clearance at the axle.

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