Brake Troubleshooting Expert

I am online and ready. I am your Commercial Vehicle Braking and Suspension Expert, specializing in Meritor, Knorr/Bendix, and WABCO systems. I am fully integrated with the Fraser Gauge catalog.

What vehicle and brake issue are we troubleshooting today?

I can help with:

• Meritor EX225 disc brake calipers
• Knorr-Bremse / Bendix SN7, SB7, SYD7, ADB22X systems
• WABCO PAN 17, PAN 19, PAN 22, MAXXUS systems
• Air brake chambers, adjusters, rotors, and drums
• Transit buses, Class 8 trucks, and city refuse vehicles

⚠️ Safety First: Always chock wheels, cage springs, and exhaust air pressure before beginning any brake system work.

Hello — I'm the Fraser Gauge Technical Support Assistant. Whether you're a fleet manager, technician, or procurement buyer, I'm here to help. What can I assist you with today?

I understand you're experiencing excessive stroke adjustment on your S-cam brakes. This is a critical issue that needs immediate attention.

Here are the most likely root causes, in order of probability:

1. Worn Brake Linings/Shoes: As linings wear, the slack adjuster has to compensate for more travel, leading to excessive stroke.
2. Automatic Slack Adjuster Malfunction: The slack adjuster itself may be faulty, not adjusting correctly, or seized.
3. Worn S-cam Bushings or Rollers: Excessive play in the S-cam shaft bushings or worn rollers can prevent proper shoe-to-drum contact, requiring more stroke.

First diagnostic step:

Visually inspect the brake linings for wear. If they are within specification, check the operation of the automatic slack adjuster. With the wheels chocked and air pressure built, apply and release the brakes several times while observing the slack adjuster's movement. It should make small adjustments. If it's not adjusting, or if there's excessive play in the S-cam shaft, further investigation is needed.

For your specific vehicle, always refer to the OEM service manual for final torque specifications and safety procedures.