Tire Size Box

225/70R17 vs 245/70R17

245/70R17 compared with 225/70R17

+3.7% diameter, +0.8" width

245/70R17 is 30.50" tall vs 29.40". More than the 3% rule of thumb, so check carefully before switching.

29.4"17" rim6.2"8.9" wide
225/70R17 (solid) compared with 245/70R17 (dashed outline), drawn to scale

With 245/70R17 tires, when your speedometer says 60 mph you are really going

62.2 mph

245/70R17 is +1.10 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/70R17245/70R17Difference%
Overall diameter29.40"30.50"+1.10"+3.7%
Section width8.86"9.65"+0.79"+8.9%
Sidewall height6.20"6.75"+0.55"+8.9%
Circumference92.37"95.83"+3.46"+3.7%
Revolutions per mile686.0661.2−24.8−3.6%

Speedometer difference

If your vehicle came with 225/70R17 and you fit 245/70R17, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.9 mph+1.9 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph83.0 mph+3.0 mph

Each size on its own

Questions

Which is bigger, 225/70R17 or 245/70R17?
245/70R17 is taller by 1.10 inches (30.50" vs 29.40"). 245/70R17 is wider by 0.79 inches.
Can I replace 225/70R17 with 245/70R17?
It is not recommended without checking carefully. The diameter difference is +3.7%, 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 245/70R17 change my speedometer?
When your speedometer reads 60 mph with 245/70R17 fitted (calibrated for 225/70R17), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 245/70R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.55 inches of ground clearance at the axle.

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