Tire Size Box

335/55R18 vs 335/65R18

335/65R18 compared with 335/55R18

+8.1% diameter, 0.0" width

335/65R18 is 35.15" tall vs 32.51". More than the 3% rule of thumb, so check carefully before switching.

32.5"18" rim7.3"13.2" wide
335/55R18 (solid) compared with 335/65R18 (dashed outline), drawn to scale

With 335/65R18 tires, when your speedometer says 60 mph you are really going

64.9 mph

335/65R18 is +2.64 inches (+8.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

335/55R18335/65R18Difference%
Overall diameter32.51"35.15"+2.64"+8.1%
Section width13.19"13.19"0.00"0.0%
Sidewall height7.25"8.57"+1.32"+18.2%
Circumference102.13"110.41"+8.29"+8.1%
Revolutions per mile620.4573.8−46.6−7.5%

Speedometer difference

If your vehicle came with 335/55R18 and you fit 335/65R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.6 mph+1.6 mph
30 mph32.4 mph+2.4 mph
40 mph43.2 mph+3.2 mph
50 mph54.1 mph+4.1 mph
60 mph64.9 mph+4.9 mph
65 mph70.3 mph+5.3 mph
70 mph75.7 mph+5.7 mph
75 mph81.1 mph+6.1 mph
80 mph86.5 mph+6.5 mph

Each size on its own

Questions

Which is bigger, 335/55R18 or 335/65R18?
335/65R18 is taller by 2.64 inches (35.15" vs 32.51"). 335/55R18 is the same width.
Can I replace 335/55R18 with 335/65R18?
It is not recommended without checking carefully. The diameter difference is +8.1%, 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 335/65R18 change my speedometer?
When your speedometer reads 60 mph with 335/65R18 fitted (calibrated for 335/55R18), your real speed is 64.9 mph. Your odometer will under-count miles by about 8.1%.
Will 335/65R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.32 inches of ground clearance at the axle.

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