Tire Size Box

245/80R15 vs 245/85R15

245/85R15 compared with 245/80R15

+3.2% diameter, 0.0" width

245/85R15 is 31.40" tall vs 30.43". More than the 3% rule of thumb, so check carefully before switching.

30.4"15" rim7.7"9.6" wide
245/80R15 (solid) compared with 245/85R15 (dashed outline), drawn to scale

With 245/85R15 tires, when your speedometer says 60 mph you are really going

61.9 mph

245/85R15 is +0.96 inches (+3.2%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/80R15245/85R15Difference%
Overall diameter30.43"31.40"+0.96"+3.2%
Section width9.65"9.65"0.00"0.0%
Sidewall height7.72"8.20"+0.48"+6.3%
Circumference95.61"98.64"+3.03"+3.2%
Revolutions per mile662.7642.3−20.4−3.1%

Speedometer difference

If your vehicle came with 245/80R15 and you fit 245/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.6 mph+0.6 mph
30 mph31.0 mph+1.0 mph
40 mph41.3 mph+1.3 mph
50 mph51.6 mph+1.6 mph
60 mph61.9 mph+1.9 mph
65 mph67.1 mph+2.1 mph
70 mph72.2 mph+2.2 mph
75 mph77.4 mph+2.4 mph
80 mph82.5 mph+2.5 mph

Each size on its own

Questions

Which is bigger, 245/80R15 or 245/85R15?
245/85R15 is taller by 0.96 inches (31.40" vs 30.43"). 245/80R15 is the same width.
Can I replace 245/80R15 with 245/85R15?
It is not recommended without checking carefully. The diameter difference is +3.2%, 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 245/85R15 change my speedometer?
When your speedometer reads 60 mph with 245/85R15 fitted (calibrated for 245/80R15), your real speed is 61.9 mph. Your odometer will under-count miles by about 3.2%.
Will 245/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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