Tire Size Box

325/35R22 vs 325/40R22

325/40R22 compared with 325/35R22

+4.1% diameter, 0.0" width

325/40R22 is 32.24" tall vs 30.96". More than the 3% rule of thumb, so check carefully before switching.

31.0"22" rim4.5"12.8" wide
325/35R22 (solid) compared with 325/40R22 (dashed outline), drawn to scale

With 325/40R22 tires, when your speedometer says 60 mph you are really going

62.5 mph

325/40R22 is +1.28 inches (+4.1%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/35R22325/40R22Difference%
Overall diameter30.96"32.24"+1.28"+4.1%
Section width12.80"12.80"0.00"0.0%
Sidewall height4.48"5.12"+0.64"+14.3%
Circumference97.25"101.27"+4.02"+4.1%
Revolutions per mile651.5625.6−25.9−4.0%

Speedometer difference

If your vehicle came with 325/35R22 and you fit 325/40R22, 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 mph41.7 mph+1.7 mph
50 mph52.1 mph+2.1 mph
60 mph62.5 mph+2.5 mph
65 mph67.7 mph+2.7 mph
70 mph72.9 mph+2.9 mph
75 mph78.1 mph+3.1 mph
80 mph83.3 mph+3.3 mph

Each size on its own

Questions

Which is bigger, 325/35R22 or 325/40R22?
325/40R22 is taller by 1.28 inches (32.24" vs 30.96"). 325/35R22 is the same width.
Can I replace 325/35R22 with 325/40R22?
It is not recommended without checking carefully. The diameter difference is +4.1%, 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 325/40R22 change my speedometer?
When your speedometer reads 60 mph with 325/40R22 fitted (calibrated for 325/35R22), your real speed is 62.5 mph. Your odometer will under-count miles by about 4.1%.
Will 325/40R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.64 inches of ground clearance at the axle.

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