Tire Size Box

275/80R15 vs 275/85R15

275/85R15 compared with 275/80R15

+3.3% diameter, 0.0" width

275/85R15 is 33.41" tall vs 32.32". More than the 3% rule of thumb, so check carefully before switching.

32.3"15" rim8.7"10.8" wide
275/80R15 (solid) compared with 275/85R15 (dashed outline), drawn to scale

With 275/85R15 tires, when your speedometer says 60 mph you are really going

62.0 mph

275/85R15 is +1.08 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

275/80R15275/85R15Difference%
Overall diameter32.32"33.41"+1.08"+3.3%
Section width10.83"10.83"0.00"0.0%
Sidewall height8.66"9.20"+0.54"+6.3%
Circumference101.55"104.95"+3.40"+3.3%
Revolutions per mile624.0603.7−20.2−3.2%

Speedometer difference

If your vehicle came with 275/80R15 and you fit 275/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.7 mph+1.7 mph
60 mph62.0 mph+2.0 mph
65 mph67.2 mph+2.2 mph
70 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.7 mph+2.7 mph

Each size on its own

Questions

Which is bigger, 275/80R15 or 275/85R15?
275/85R15 is taller by 1.08 inches (33.41" vs 32.32"). 275/80R15 is the same width.
Can I replace 275/80R15 with 275/85R15?
It is not recommended without checking carefully. The diameter difference is +3.3%, 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 275/85R15 change my speedometer?
When your speedometer reads 60 mph with 275/85R15 fitted (calibrated for 275/80R15), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 275/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.54 inches of ground clearance at the axle.

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