Tire Size Box

335/45R18 vs 335/55R18

335/55R18 compared with 335/45R18

+8.8% diameter, 0.0" width

335/55R18 is 32.51" tall vs 29.87". More than the 3% rule of thumb, so check carefully before switching.

29.9"18" rim5.9"13.2" wide
335/45R18 (solid) compared with 335/55R18 (dashed outline), drawn to scale

With 335/55R18 tires, when your speedometer says 60 mph you are really going

65.3 mph

335/55R18 is +2.64 inches (+8.8%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/45R18335/55R18Difference%
Overall diameter29.87"32.51"+2.64"+8.8%
Section width13.19"13.19"0.00"0.0%
Sidewall height5.94"7.25"+1.32"+22.2%
Circumference93.84"102.13"+8.29"+8.8%
Revolutions per mile675.2620.4−54.8−8.1%

Speedometer difference

If your vehicle came with 335/45R18 and you fit 335/55R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.8 mph+1.8 mph
30 mph32.6 mph+2.6 mph
40 mph43.5 mph+3.5 mph
50 mph54.4 mph+4.4 mph
60 mph65.3 mph+5.3 mph
65 mph70.7 mph+5.7 mph
70 mph76.2 mph+6.2 mph
75 mph81.6 mph+6.6 mph
80 mph87.1 mph+7.1 mph

Each size on its own

Questions

Which is bigger, 335/45R18 or 335/55R18?
335/55R18 is taller by 2.64 inches (32.51" vs 29.87"). 335/45R18 is the same width.
Can I replace 335/45R18 with 335/55R18?
It is not recommended without checking carefully. The diameter difference is +8.8%, 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 335/55R18 change my speedometer?
When your speedometer reads 60 mph with 335/55R18 fitted (calibrated for 335/45R18), your real speed is 65.3 mph. Your odometer will under-count miles by about 8.8%.
Will 335/55R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.32 inches of ground clearance at the axle.

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