Doing an annual on a tandem dump with Type 30 brake chambers.

For Type 30 brake chambers, the maximum allowable pushrod stroke is 1.5 inches (measured from the chamber housing to the center of the pushrod clevis pin).

How to measure:

1. Chock wheels and release parking brakes so the chamber is fully released.
2. Mark the pushrod at the point where it exits the chamber housing face.
3. Apply the brake fully (either by foot valve or by having someone apply the brakes) and hold.
4. Measure from the chamber housing face to the center of the clevis pin (or mark) while the brake is applied. This is the applied stroke.
5. Compare to the 1.5-inch limit.

Important notes:

• If stroke exceeds 1.5", the chamber must be adjusted or replaced — do not use shims to compensate.
• Check both stroke and chamber condition — excessive stroke often indicates internal wear or improper adjustment.
• Per CVSA North American Standard Out-of-Service Criteria, a pushrod stroke exceeding 1.5 inches on a Type 30 chamber is grounds for out-of-service.

Also verify the slack adjuster is properly lubricated and not worn, as this affects stroke readings. If you're consistently seeing near-limit strokes, investigate the entire brake system geometry.

Pushrod Stroke Limit (Type 30):

• Standard Stroke (2.5" rated): 2 inches (CVSA/OOS criteria).
• Long Stroke (3.0" rated - square port): 2.5 inches.
• Verify chamber rating: Check the clamp band tag or body marking. If it says "Type 30" only, it's standard (2" limit). If marked "Type 30LS" or "3.0", it's long stroke (2.5" limit). 49 CFR 393.47(d)(2); CVSA OOS Criteria.

Measurement Procedure (Applied Stroke Method - Standard Annual Check):

1. Prep: Chock wheels. Release spring brakes (cage if necessary, but prefer supply air). Engine OFF, key in pocket. Reservoir pressure 90–100 psi.
2. Mark: With brakes released, mark the pushrod at the face of the brake chamber (or fixed reference point on chamber) using chalk/marker/tape.
3. Apply: Have assistant make a full service brake application (treadle valve fully depressed). Hold application.
4. Measure: Measure distance from mark to chamber face (or reference point). This is your applied stroke.
5. Compare: Must be ≤ 2" (std) or ≤ 2.5" (LS).
6. Adjust if Over: If over limit, adjust slack adjuster (manual) or diagnose ASA (auto). Re-measure after adjustment.

Critical Notes:

• Measure ALL chambers. Tandem = 4 chambers (usually). One OOS puts truck OOS.
• Angle: Pushrod must be 90° to slack adjuster at applied position. If not, bracket/slack geometry is wrong – fix before measuring.
• Auto Slacks (ASA): Do not manually adjust routinely. If stroke > limit, ASA is faulty (worn, seized, wrong install). Diagnose/replace per mfr procedure. Manual adjustment masks the fault.
• Spring Brake Check: After service check, apply spring brakes (pull valve). Pushrod should not move further. If it does, service brake adjustment is insufficient or spring brake mechanism faulty.

Reference: FMCSR 393.47, 396.17, 396.25; CVSA North American Standard Out-of-Service Criteria (Brake Section).