Tire Size Box

235/55R18 vs 235/60R18

235/60R18 compared with 235/55R18

+3.3% diameter, 0.0" width

235/60R18 is 29.10" tall vs 28.18". More than the 3% rule of thumb, so check carefully before switching.

28.2"18" rim5.1"9.3" wide
235/55R18 (solid) compared with 235/60R18 (dashed outline), drawn to scale

With 235/60R18 tires, when your speedometer says 60 mph you are really going

62.0 mph

235/60R18 is +0.93 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

235/55R18235/60R18Difference%
Overall diameter28.18"29.10"+0.93"+3.3%
Section width9.25"9.25"0.00"0.0%
Sidewall height5.09"5.55"+0.46"+9.1%
Circumference88.52"91.43"+2.91"+3.3%
Revolutions per mile715.8693.0−22.8−3.2%

Speedometer difference

If your vehicle came with 235/55R18 and you fit 235/60R18, 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 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 235/55R18 or 235/60R18?
235/60R18 is taller by 0.93 inches (29.10" vs 28.18"). 235/55R18 is the same width.
Can I replace 235/55R18 with 235/60R18?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 235/60R18 change my speedometer?
When your speedometer reads 60 mph with 235/60R18 fitted (calibrated for 235/55R18), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 235/60R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.46 inches of ground clearance at the axle.

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