Tire Size Box

285/65R18 vs 285/75R18

285/75R18 compared with 285/65R18

+6.9% diameter, 0.0" width

285/75R18 is 34.83" tall vs 32.59". More than the 3% rule of thumb, so check carefully before switching.

32.6"18" rim7.3"11.2" wide
285/65R18 (solid) compared with 285/75R18 (dashed outline), drawn to scale

With 285/75R18 tires, when your speedometer says 60 mph you are really going

64.1 mph

285/75R18 is +2.24 inches (+6.9%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/65R18285/75R18Difference%
Overall diameter32.59"34.83"+2.24"+6.9%
Section width11.22"11.22"0.00"0.0%
Sidewall height7.29"8.42"+1.12"+15.4%
Circumference102.37"109.42"+7.05"+6.9%
Revolutions per mile618.9579.0−39.9−6.4%

Speedometer difference

If your vehicle came with 285/65R18 and you fit 285/75R18, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.1 mph+2.1 mph
40 mph42.8 mph+2.8 mph
50 mph53.4 mph+3.4 mph
60 mph64.1 mph+4.1 mph
65 mph69.5 mph+4.5 mph
70 mph74.8 mph+4.8 mph
75 mph80.2 mph+5.2 mph
80 mph85.5 mph+5.5 mph

Each size on its own

Questions

Which is bigger, 285/65R18 or 285/75R18?
285/75R18 is taller by 2.24 inches (34.83" vs 32.59"). 285/65R18 is the same width.
Can I replace 285/65R18 with 285/75R18?
It is not recommended without checking carefully. The diameter difference is +6.9%, 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 285/75R18 change my speedometer?
When your speedometer reads 60 mph with 285/75R18 fitted (calibrated for 285/65R18), your real speed is 64.1 mph. Your odometer will under-count miles by about 6.9%.
Will 285/75R18 lift my vehicle?
Ride height changes by half the diameter difference: +1.12 inches of ground clearance at the axle.

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