Tire Size Box

235/60R17 vs 255/60R17

255/60R17 compared with 235/60R17

+3.4% diameter, +0.8" width

255/60R17 is 29.05" tall vs 28.10". More than the 3% rule of thumb, so check carefully before switching.

28.1"17" rim5.6"9.3" wide
235/60R17 (solid) compared with 255/60R17 (dashed outline), drawn to scale

With 255/60R17 tires, when your speedometer says 60 mph you are really going

62.0 mph

255/60R17 is +0.94 inches (+3.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/60R17255/60R17Difference%
Overall diameter28.10"29.05"+0.94"+3.4%
Section width9.25"10.04"+0.79"+8.5%
Sidewall height5.55"6.02"+0.47"+8.5%
Circumference88.29"91.25"+2.97"+3.4%
Revolutions per mile717.7694.3−23.3−3.3%

Speedometer difference

If your vehicle came with 235/60R17 and you fit 255/60R17, 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 mph41.3 mph+1.3 mph
50 mph51.7 mph+1.7 mph
60 mph62.0 mph+2.0 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.5 mph+2.5 mph
80 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 235/60R17 or 255/60R17?
255/60R17 is taller by 0.94 inches (29.05" vs 28.10"). 255/60R17 is wider by 0.79 inches.
Can I replace 235/60R17 with 255/60R17?
It is not recommended without checking carefully. The diameter difference is +3.4%, 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 255/60R17 change my speedometer?
When your speedometer reads 60 mph with 255/60R17 fitted (calibrated for 235/60R17), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.4%.
Will 255/60R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.47 inches of ground clearance at the axle.

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