Tire Size Box

245/75R15 vs 245/80R15

245/80R15 compared with 245/75R15

+3.3% diameter, 0.0" width

245/80R15 is 30.43" tall vs 29.47". More than the 3% rule of thumb, so check carefully before switching.

29.5"15" rim7.2"9.6" wide
245/75R15 (solid) compared with 245/80R15 (dashed outline), drawn to scale

With 245/80R15 tires, when your speedometer says 60 mph you are really going

62.0 mph

245/80R15 is +0.96 inches (+3.3%) in overall diameter. That is more than the 3% most shops and makers recommend.

245/75R15245/80R15Difference%
Overall diameter29.47"30.43"+0.96"+3.3%
Section width9.65"9.65"0.00"0.0%
Sidewall height7.23"7.72"+0.48"+6.7%
Circumference92.58"95.61"+3.03"+3.3%
Revolutions per mile684.4662.7−21.7−3.2%

Speedometer difference

If your vehicle came with 245/75R15 and you fit 245/80R15, 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 mph51.6 mph+1.6 mph
60 mph62.0 mph+2.0 mph
65 mph67.1 mph+2.1 mph
70 mph72.3 mph+2.3 mph
75 mph77.5 mph+2.5 mph
80 mph82.6 mph+2.6 mph

Each size on its own

Questions

Which is bigger, 245/75R15 or 245/80R15?
245/80R15 is taller by 0.96 inches (30.43" vs 29.47"). 245/75R15 is the same width.
Can I replace 245/75R15 with 245/80R15?
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 245/80R15 change my speedometer?
When your speedometer reads 60 mph with 245/80R15 fitted (calibrated for 245/75R15), your real speed is 62.0 mph. Your odometer will under-count miles by about 3.3%.
Will 245/80R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.48 inches of ground clearance at the axle.

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