Tire Size Box

205/70R15 vs 205/80R15

205/80R15 compared with 205/70R15

+6.1% diameter, 0.0" width

205/80R15 is 27.91" tall vs 26.30". More than the 3% rule of thumb, so check carefully before switching.

26.3"15" rim5.6"8.1" wide
205/70R15 (solid) compared with 205/80R15 (dashed outline), drawn to scale

With 205/80R15 tires, when your speedometer says 60 mph you are really going

63.7 mph

205/80R15 is +1.61 inches (+6.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

205/70R15205/80R15Difference%
Overall diameter26.30"27.91"+1.61"+6.1%
Section width8.07"8.07"0.00"0.0%
Sidewall height5.65"6.46"+0.81"+14.3%
Circumference82.62"87.69"+5.07"+6.1%
Revolutions per mile766.9722.5−44.3−5.8%

Speedometer difference

If your vehicle came with 205/70R15 and you fit 205/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.2 mph+1.2 mph
30 mph31.8 mph+1.8 mph
40 mph42.5 mph+2.5 mph
50 mph53.1 mph+3.1 mph
60 mph63.7 mph+3.7 mph
65 mph69.0 mph+4.0 mph
70 mph74.3 mph+4.3 mph
75 mph79.6 mph+4.6 mph
80 mph84.9 mph+4.9 mph

Each size on its own

Questions

Which is bigger, 205/70R15 or 205/80R15?
205/80R15 is taller by 1.61 inches (27.91" vs 26.30"). 205/70R15 is the same width.
Can I replace 205/70R15 with 205/80R15?
It is not recommended without checking carefully. The diameter difference is +6.1%, 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 205/80R15 change my speedometer?
When your speedometer reads 60 mph with 205/80R15 fitted (calibrated for 205/70R15), your real speed is 63.7 mph. Your odometer will under-count miles by about 6.1%.
Will 205/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.81 inches of ground clearance at the axle.

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