Tire Size Box

285/70R15 vs 285/75R15

285/75R15 compared with 285/70R15

+3.7% diameter, 0.0" width

285/75R15 is 31.83" tall vs 30.71". More than the 3% rule of thumb, so check carefully before switching.

30.7"15" rim7.9"11.2" wide
285/70R15 (solid) compared with 285/75R15 (dashed outline), drawn to scale

With 285/75R15 tires, when your speedometer says 60 mph you are really going

62.2 mph

285/75R15 is +1.12 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

285/70R15285/75R15Difference%
Overall diameter30.71"31.83"+1.12"+3.7%
Section width11.22"11.22"0.00"0.0%
Sidewall height7.85"8.42"+0.56"+7.1%
Circumference96.47"100.00"+3.53"+3.7%
Revolutions per mile656.8633.6−23.2−3.5%

Speedometer difference

If your vehicle came with 285/70R15 and you fit 285/75R15, 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 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.7 mph+2.7 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 285/70R15 or 285/75R15?
285/75R15 is taller by 1.12 inches (31.83" vs 30.71"). 285/70R15 is the same width.
Can I replace 285/70R15 with 285/75R15?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 285/75R15 change my speedometer?
When your speedometer reads 60 mph with 285/75R15 fitted (calibrated for 285/70R15), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 285/75R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.56 inches of ground clearance at the axle.

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