Tire Size Box

285/75R15 vs 285/80R15

285/80R15 compared with 285/75R15

+3.5% diameter, 0.0" width

285/80R15 is 32.95" tall vs 31.83". More than the 3% rule of thumb, so check carefully before switching.

31.8"15" rim8.4"11.2" wide
285/75R15 (solid) compared with 285/80R15 (dashed outline), drawn to scale

With 285/80R15 tires, when your speedometer says 60 mph you are really going

62.1 mph

285/80R15 is +1.12 inches (+3.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/75R15285/80R15Difference%
Overall diameter31.83"32.95"+1.12"+3.5%
Section width11.22"11.22"0.00"0.0%
Sidewall height8.42"8.98"+0.56"+6.7%
Circumference100.00"103.52"+3.53"+3.5%
Revolutions per mile633.6612.0−21.6−3.4%

Speedometer difference

If your vehicle came with 285/75R15 and you fit 285/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.4 mph+1.4 mph
50 mph51.8 mph+1.8 mph
60 mph62.1 mph+2.1 mph
65 mph67.3 mph+2.3 mph
70 mph72.5 mph+2.5 mph
75 mph77.6 mph+2.6 mph
80 mph82.8 mph+2.8 mph

Each size on its own

Questions

Which is bigger, 285/75R15 or 285/80R15?
285/80R15 is taller by 1.12 inches (32.95" vs 31.83"). 285/75R15 is the same width.
Can I replace 285/75R15 with 285/80R15?
It is not recommended without checking carefully. The diameter difference is +3.5%, 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 285/80R15 change my speedometer?
When your speedometer reads 60 mph with 285/80R15 fitted (calibrated for 285/75R15), your real speed is 62.1 mph. Your odometer will under-count miles by about 3.5%.
Will 285/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.56 inches of ground clearance at the axle.

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