Tire Size Box

225/70R15 vs 245/70R15

245/70R15 compared with 225/70R15

+4.0% diameter, +0.8" width

245/70R15 is 28.50" tall vs 27.40". More than the 3% rule of thumb, so check carefully before switching.

27.4"15" rim6.2"8.9" wide
225/70R15 (solid) compared with 245/70R15 (dashed outline), drawn to scale

With 245/70R15 tires, when your speedometer says 60 mph you are really going

62.4 mph

245/70R15 is +1.10 inches (+4.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/70R15245/70R15Difference%
Overall diameter27.40"28.50"+1.10"+4.0%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height6.20"6.75"+0.55"+8.9%
Circumference86.08"89.55"+3.46"+4.0%
Revolutions per mile736.0707.6−28.5−3.9%

Speedometer difference

If your vehicle came with 225/70R15 and you fit 245/70R15, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.8 mph+0.8 mph
30 mph31.2 mph+1.2 mph
40 mph41.6 mph+1.6 mph
50 mph52.0 mph+2.0 mph
60 mph62.4 mph+2.4 mph
65 mph67.6 mph+2.6 mph
70 mph72.8 mph+2.8 mph
75 mph78.0 mph+3.0 mph
80 mph83.2 mph+3.2 mph

Each size on its own

Questions

Which is bigger, 225/70R15 or 245/70R15?
245/70R15 is taller by 1.10 inches (28.50" vs 27.40"). 245/70R15 is wider by 0.79 inches.
Can I replace 225/70R15 with 245/70R15?
It is not recommended without checking carefully. The diameter difference is +4.0%, 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 245/70R15 change my speedometer?
When your speedometer reads 60 mph with 245/70R15 fitted (calibrated for 225/70R15), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.0%.
Will 245/70R15 lift my vehicle?
Ride height changes by half the diameter difference: +0.55 inches of ground clearance at the axle.

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