Tire Size Box

175/75R15 vs 175/85R15

175/85R15 compared with 175/75R15

+5.4% diameter, 0.0" width

175/85R15 is 26.71" tall vs 25.33". More than the 3% rule of thumb, so check carefully before switching.

25.3"15" rim5.2"6.9" wide
175/75R15 (solid) compared with 175/85R15 (dashed outline), drawn to scale

With 175/85R15 tires, when your speedometer says 60 mph you are really going

63.3 mph

175/85R15 is +1.38 inches (+5.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

175/75R15175/85R15Difference%
Overall diameter25.33"26.71"+1.38"+5.4%
Section width6.89"6.89"0.00"0.0%
Sidewall height5.17"5.86"+0.69"+13.3%
Circumference79.59"83.92"+4.33"+5.4%
Revolutions per mile796.1755.0−41.1−5.2%

Speedometer difference

If your vehicle came with 175/75R15 and you fit 175/85R15, 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 mph42.2 mph+2.2 mph
50 mph52.7 mph+2.7 mph
60 mph63.3 mph+3.3 mph
65 mph68.5 mph+3.5 mph
70 mph73.8 mph+3.8 mph
75 mph79.1 mph+4.1 mph
80 mph84.4 mph+4.4 mph

Each size on its own

Questions

Which is bigger, 175/75R15 or 175/85R15?
175/85R15 is taller by 1.38 inches (26.71" vs 25.33"). 175/75R15 is the same width.
Can I replace 175/75R15 with 175/85R15?
It is not recommended without checking carefully. The diameter difference is +5.4%, 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 175/85R15 change my speedometer?
When your speedometer reads 60 mph with 175/85R15 fitted (calibrated for 175/75R15), your real speed is 63.3 mph. Your odometer will under-count miles by about 5.4%.
Will 175/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.69 inches of ground clearance at the axle.

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