Tire Size Box

265/55R18 vs 285/55R18

285/55R18 compared with 265/55R18

+2.9% diameter, +0.8" width

285/55R18 is 30.34" tall vs 29.48". Within the 3% rule, so usually interchangeable.

29.5"18" rim5.7"10.4" wide
265/55R18 (solid) compared with 285/55R18 (dashed outline), drawn to scale

With 285/55R18 tires, when your speedometer says 60 mph you are really going

61.8 mph

285/55R18 is +0.87 inches (+2.9%) in overall diameter. That is within the 3% most shops and makers allow.

265/55R18285/55R18Difference%
Overall diameter29.48"30.34"+0.87"+2.9%
Section width10.43"11.22"+0.79"+7.5%
Sidewall height5.74"6.17"+0.43"+7.5%
Circumference92.60"95.32"+2.72"+2.9%
Revolutions per mile684.2664.7−19.5−2.9%

Speedometer difference

If your vehicle came with 265/55R18 and you fit 285/55R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph30.9 mph+0.9 mph
40 mph41.2 mph+1.2 mph
50 mph51.5 mph+1.5 mph
60 mph61.8 mph+1.8 mph
65 mph66.9 mph+1.9 mph
70 mph72.1 mph+2.1 mph
75 mph77.2 mph+2.2 mph
80 mph82.4 mph+2.4 mph

Each size on its own

Questions

Which is bigger, 265/55R18 or 285/55R18?
285/55R18 is taller by 0.87 inches (30.34" vs 29.48"). 285/55R18 is wider by 0.79 inches.
Can I replace 265/55R18 with 285/55R18?
Usually, yes. The diameter difference is +2.9%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 285/55R18 change my speedometer?
When your speedometer reads 60 mph with 285/55R18 fitted (calibrated for 265/55R18), your real speed is 61.8 mph. Your odometer will under-count miles by about 2.9%.
Will 285/55R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.43 inches of ground clearance at the axle.

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