Tire Size Box

285/65R18 vs 285/70R18

285/70R18 compared with 285/65R18

+3.4% diameter, 0.0" width

285/70R18 is 33.71" 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 285/70R18 (dashed outline), drawn to scale

With 285/70R18 tires, when your speedometer says 60 mph you are really going

62.1 mph

285/70R18 is +1.12 inches (+3.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/65R18285/70R18Difference%
Overall diameter32.59"33.71"+1.12"+3.4%
Section width11.22"11.22"0.00"0.0%
Sidewall height7.29"7.85"+0.56"+7.7%
Circumference102.37"105.90"+3.53"+3.4%
Revolutions per mile618.9598.3−20.6−3.3%

Speedometer difference

If your vehicle came with 285/65R18 and you fit 285/70R18, 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 mph41.4 mph+1.4 mph
50 mph51.7 mph+1.7 mph
60 mph62.1 mph+2.1 mph
65 mph67.2 mph+2.2 mph
70 mph72.4 mph+2.4 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 285/65R18 or 285/70R18?
285/70R18 is taller by 1.12 inches (33.71" vs 32.59"). 285/65R18 is the same width.
Can I replace 285/65R18 with 285/70R18?
It is not recommended without checking carefully. The diameter difference is +3.4%, 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 285/70R18 change my speedometer?
When your speedometer reads 60 mph with 285/70R18 fitted (calibrated for 285/65R18), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.4%.
Will 285/70R18 lift my vehicle?
Ride height changes by half the diameter difference: +0.56 inches of ground clearance at the axle.

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