Tire Size Box

235/55R14 vs 255/55R14

255/55R14 compared with 235/55R14

+3.6% diameter, +0.8" width

255/55R14 is 25.04" tall vs 24.18". More than the 3% rule of thumb, so check carefully before switching.

24.2"14" rim5.1"9.3" wide
235/55R14 (solid) compared with 255/55R14 (dashed outline), drawn to scale

With 255/55R14 tires, when your speedometer says 60 mph you are really going

62.1 mph

255/55R14 is +0.87 inches (+3.6%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/55R14255/55R14Difference%
Overall diameter24.18"25.04"+0.87"+3.6%
Section width9.25"10.04"+0.79"+8.5%
Sidewall height5.09"5.52"+0.43"+8.5%
Circumference75.95"78.68"+2.72"+3.6%
Revolutions per mile834.2805.3−28.9−3.5%

Speedometer difference

If your vehicle came with 235/55R14 and you fit 255/55R14, 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 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 235/55R14 or 255/55R14?
255/55R14 is taller by 0.87 inches (25.04" vs 24.18"). 255/55R14 is wider by 0.79 inches.
Can I replace 235/55R14 with 255/55R14?
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 255/55R14 change my speedometer?
When your speedometer reads 60 mph with 255/55R14 fitted (calibrated for 235/55R14), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.6%.
Will 255/55R14 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

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