Tire Size Box

225/85R15 vs 245/85R15

245/85R15 compared with 225/85R15

+4.5% diameter, +0.8" width

245/85R15 is 31.40" tall vs 30.06". More than the 3% rule of thumb, so check carefully before switching.

30.1"15" rim7.5"8.9" wide
225/85R15 (solid) compared with 245/85R15 (dashed outline), drawn to scale

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

62.7 mph

245/85R15 is +1.34 inches (+4.5%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/85R15245/85R15Difference%
Overall diameter30.06"31.40"+1.34"+4.5%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height7.53"8.20"+0.67"+8.9%
Circumference94.43"98.64"+4.21"+4.5%
Revolutions per mile670.9642.3−28.6−4.3%

Speedometer difference

If your vehicle came with 225/85R15 and you fit 245/85R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.9 mph+0.9 mph
30 mph31.3 mph+1.3 mph
40 mph41.8 mph+1.8 mph
50 mph52.2 mph+2.2 mph
60 mph62.7 mph+2.7 mph
65 mph67.9 mph+2.9 mph
70 mph73.1 mph+3.1 mph
75 mph78.3 mph+3.3 mph
80 mph83.6 mph+3.6 mph

Each size on its own

Questions

Which is bigger, 225/85R15 or 245/85R15?
245/85R15 is taller by 1.34 inches (31.40" vs 30.06"). 245/85R15 is wider by 0.79 inches.
Can I replace 225/85R15 with 245/85R15?
It is not recommended without checking carefully. The diameter difference is +4.5%, 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 225/85R15), your real speed is 62.7 mph. Your odometer will under-count miles by about 4.5%.
Will 245/85R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.67 inches of ground clearance at the axle.

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