Tire Size Box

225/40R17 vs 225/45R17

225/45R17 compared with 225/40R17

+3.7% diameter, 0.0" width

225/45R17 is 24.97" tall vs 24.09". More than the 3% rule of thumb, so check carefully before switching.

24.1"17" rim3.5"8.9" wide
225/40R17 (solid) compared with 225/45R17 (dashed outline), drawn to scale

With 225/45R17 tires, when your speedometer says 60 mph you are really going

62.2 mph

225/45R17 is +0.89 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

225/40R17225/45R17Difference%
Overall diameter24.09"24.97"+0.89"+3.7%
Section width8.86"8.86"0.00"0.0%
Sidewall height3.54"3.99"+0.44"+12.5%
Circumference75.67"78.45"+2.78"+3.7%
Revolutions per mile837.3807.6−29.7−3.5%

Speedometer difference

If your vehicle came with 225/40R17 and you fit 225/45R17, 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 mph51.8 mph+1.8 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 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 225/40R17 or 225/45R17?
225/45R17 is taller by 0.89 inches (24.97" vs 24.09"). 225/40R17 is the same width.
Can I replace 225/40R17 with 225/45R17?
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 225/45R17 change my speedometer?
When your speedometer reads 60 mph with 225/45R17 fitted (calibrated for 225/40R17), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 225/45R17 lift my vehicle?
Ride height changes by half the diameter difference: +0.44 inches of ground clearance at the axle.

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