Tire Size Box

275/70R15 vs 275/80R15

275/80R15 compared with 275/70R15

+7.2% diameter, 0.0" width

275/80R15 is 32.32" tall vs 30.16". More than the 3% rule of thumb, so check carefully before switching.

30.2"15" rim7.6"10.8" wide
275/70R15 (solid) compared with 275/80R15 (dashed outline), drawn to scale

With 275/80R15 tires, when your speedometer says 60 mph you are really going

64.3 mph

275/80R15 is +2.17 inches (+7.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/70R15275/80R15Difference%
Overall diameter30.16"32.32"+2.17"+7.2%
Section width10.83"10.83"0.00"0.0%
Sidewall height7.58"8.66"+1.08"+14.3%
Circumference94.74"101.55"+6.80"+7.2%
Revolutions per mile668.8624.0−44.8−6.7%

Speedometer difference

If your vehicle came with 275/70R15 and you fit 275/80R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph21.4 mph+1.4 mph
30 mph32.2 mph+2.2 mph
40 mph42.9 mph+2.9 mph
50 mph53.6 mph+3.6 mph
60 mph64.3 mph+4.3 mph
65 mph69.7 mph+4.7 mph
70 mph75.0 mph+5.0 mph
75 mph80.4 mph+5.4 mph
80 mph85.7 mph+5.7 mph

Each size on its own

Questions

Which is bigger, 275/70R15 or 275/80R15?
275/80R15 is taller by 2.17 inches (32.32" vs 30.16"). 275/70R15 is the same width.
Can I replace 275/70R15 with 275/80R15?
It is not recommended without checking carefully. The diameter difference is +7.2%, 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 275/80R15 change my speedometer?
When your speedometer reads 60 mph with 275/80R15 fitted (calibrated for 275/70R15), your real speed is 64.3 mph. Your odometer will under-count miles by about 7.2%.
Will 275/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +1.08 inches of ground clearance at the axle.

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