Tire Size Box

165/70R15 vs 165/80R15

165/80R15 compared with 165/70R15

+5.4% diameter, 0.0" width

165/80R15 is 25.39" tall vs 24.09". More than the 3% rule of thumb, so check carefully before switching.

24.1"15" rim4.5"6.5" wide
165/70R15 (solid) compared with 165/80R15 (dashed outline), drawn to scale

With 165/80R15 tires, when your speedometer says 60 mph you are really going

63.2 mph

165/80R15 is +1.30 inches (+5.4%) in overall diameter. That is more than the 3% most shops and makers recommend.

165/70R15165/80R15Difference%
Overall diameter24.09"25.39"+1.30"+5.4%
Section width6.50"6.50"0.00"0.0%
Sidewall height4.55"5.20"+0.65"+14.3%
Circumference75.70"79.78"+4.08"+5.4%
Revolutions per mile837.0794.2−42.8−5.1%

Speedometer difference

If your vehicle came with 165/70R15 and you fit 165/80R15, 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 mph63.2 mph+3.2 mph
65 mph68.5 mph+3.5 mph
70 mph73.8 mph+3.8 mph
75 mph79.0 mph+4.0 mph
80 mph84.3 mph+4.3 mph

Each size on its own

Questions

Which is bigger, 165/70R15 or 165/80R15?
165/80R15 is taller by 1.30 inches (25.39" vs 24.09"). 165/70R15 is the same width.
Can I replace 165/70R15 with 165/80R15?
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 165/80R15 change my speedometer?
When your speedometer reads 60 mph with 165/80R15 fitted (calibrated for 165/70R15), your real speed is 63.2 mph. Your odometer will under-count miles by about 5.4%.
Will 165/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.65 inches of ground clearance at the axle.

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