SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/cdl-air-leak-rate-limit

In the applied leakage test, how much air may a combination vehicle lose in one minute?

No more than 4 psi.

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  1. 1 psi
  2. 10 psi
  3. 4 psi ✔

Why: Build air to cut-out, shut off the engine, release the parking brake and hold the foot brake for one minute. A single vehicle may lose 3 psi, a combination 4 psi.

Huh, didn't know that: With all brakes released (static test), the limits are lower: 2 psi single, 3 psi combination.

The dad joke
Why did the trucker time the air gauge? Every second counts on a pre-trip.
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References

Answer: 4 psi. Build air to cut-out, shut off the engine, release the parking brake and hold the foot brake for one minute. A single vehicle may lose 3 psi, a combination 4 psi.

  1. Texas Commercial Driver's License Manual (DPS) www.dps.texas.gov/internetforms/Forms/DL-7C.pdf
    drops more than three pounds in one minute (single vehicle) or four pounds in one minute (combination vehicle).
    Checked 2026-10-10.

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