Tire Size Box

165/75R15 vs 165/85R15

165/85R15 compared with 165/75R15

+5.3% diameter, 0.0" width

165/85R15 is 26.04" tall vs 24.74". More than the 3% rule of thumb, so check carefully before switching.

24.7"15" rim4.9"6.5" wide
165/75R15 (solid) compared with 165/85R15 (dashed outline), drawn to scale

With 165/85R15 tires, when your speedometer says 60 mph you are really going

63.2 mph

165/85R15 is +1.30 inches (+5.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

165/75R15165/85R15Difference%
Overall diameter24.74"26.04"+1.30"+5.3%
Section width6.50"6.50"0.00"0.0%
Sidewall height4.87"5.52"+0.65"+13.3%
Circumference77.74"81.82"+4.08"+5.3%
Revolutions per mile815.1774.4−40.7−5.0%

Speedometer difference

If your vehicle came with 165/75R15 and you fit 165/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.1 mph+1.1 mph
30 mph31.6 mph+1.6 mph
40 mph42.1 mph+2.1 mph
50 mph52.6 mph+2.6 mph
60 mph63.2 mph+3.2 mph
65 mph68.4 mph+3.4 mph
70 mph73.7 mph+3.7 mph
75 mph78.9 mph+3.9 mph
80 mph84.2 mph+4.2 mph

Each size on its own

Questions

Which is bigger, 165/75R15 or 165/85R15?
165/85R15 is taller by 1.30 inches (26.04" vs 24.74"). 165/75R15 is the same width.
Can I replace 165/75R15 with 165/85R15?
It is not recommended without checking carefully. The diameter difference is +5.3%, 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 165/85R15 change my speedometer?
When your speedometer reads 60 mph with 165/85R15 fitted (calibrated for 165/75R15), your real speed is 63.2 mph. Your odometer will under-count miles by about 5.3%.
Will 165/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.65 inches of ground clearance at the axle.

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