Tire Size Box

325/40R22 vs 325/45R22

325/45R22 compared with 325/40R22

+4.0% diameter, 0.0" width

325/45R22 is 33.52" tall vs 32.24". More than the 3% rule of thumb, so check carefully before switching.

32.2"22" rim5.1"12.8" wide
325/40R22 (solid) compared with 325/45R22 (dashed outline), drawn to scale

With 325/45R22 tires, when your speedometer says 60 mph you are really going

62.4 mph

325/45R22 is +1.28 inches (+4.0%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/40R22325/45R22Difference%
Overall diameter32.24"33.52"+1.28"+4.0%
Section width12.80"12.80"0.00"0.0%
Sidewall height5.12"5.76"+0.64"+12.5%
Circumference101.27"105.29"+4.02"+4.0%
Revolutions per mile625.6601.8−23.9−3.8%

Speedometer difference

If your vehicle came with 325/40R22 and you fit 325/45R22, 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, 325/40R22 or 325/45R22?
325/45R22 is taller by 1.28 inches (33.52" vs 32.24"). 325/40R22 is the same width.
Can I replace 325/40R22 with 325/45R22?
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 325/45R22 change my speedometer?
When your speedometer reads 60 mph with 325/45R22 fitted (calibrated for 325/40R22), your real speed is 62.4 mph. Your odometer will under-count miles by about 4.0%.
Will 325/45R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.64 inches of ground clearance at the axle.

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