1. ADB 1560 Air Disc Brake
This training session will review common problems in the field and general maintenance procedures.

2. Nomenclature Models ADB 1540 ADB 1560 ADB 1760
This is a view of the ARM brake model code. Note the 15 in the 1560 designates nominal rotor diameter.
Ref. Maintenance Manual 4M

3. General Information
Released in 1981 in response to NHTSA reduced stopping distance requirements.
Typically used in Fire Truck applications
Maintenance Manual 4M
Service Kits found in PB-8857
Uses an external ArvinMeritor Automatic Slack Adjuster
Utilizes Blue Pistons for steer & Green Piston for Drive axles
Plagued with multiple field issues
This is general information for the 1560

4. Identification
ArvinMeritor Automatic Slack Adjuster (Green Piston-Front Axle, Blue Piston- Rear Axles with T30 chamber)
Single piece bridge and carrier
Exposed slide pins
Requires specific pistons. Were needed for tighter adjustments due to Power screw geometry.
Single piece bridge means at least 1 slide pin needs to be removed to change out linings. Tilted out of the way.
Slide pins are exposed. It’s important to keep these free of grease, debris and corrosion.

5. ADB 1560 Typical Application
These are the typical applications.
Mainly used on fire Trucks.
Also used on Motor homes & School buses
Ref. Air Brakes Application Guidelines

6. Exploded View
This slide details the exploded view of parts. Note: this is directly out of the maintenance manual.
Ref. Maintenance Manual 4M

7. How It Works
Rotor
Brake Pad 4
1. The Air chamber push rod rotates the ASA attached to the Powershaft.
2. The Powershaft pushes the nut actuator towards the rotor.
3. The nut actuator forces the Brake piston and inboard lining against the rotor.
4. The force between the inboard lining and rotor pulls the caliper along the slide pins
Caliper
Powershaft 3 2
This details the operation of the ADB!560 caliper
The air chamber push rod rotates the ASA which in turn rotates the powershaft. Identical to a cam brake up to this point.
The rotation of the shaft forces the nut actuator to travel down the powershaft towards the disc.
The nut actuator forces the piston and lining against the rotor
The reaction force of the inboard lining on the rotor pulls the caliper along the slide pins.
This provides the proper clamping force to stop the wheel. 1
Brake piston
Nut actuator
ASA
Ref. Maintenance Manual 4M

8. Typical Air Disc Brake Problems
Over adjustment: Dragging Brakes
Under adjustment: Excessive Stroke and High worm Torque on ASA
Seizing of slide pins: Un-even pad wear and rotor cracking
Damage to Boots and seals: Seizing of internals
Poor vehicle application: Low pad/ rotor life
These are typical problems associated with Disc brakes.
Dragging brakes – due to overadjsutment
Under adjustment resulting in excessive strokes and excessive strain on ASA worm gears.
Seizing of slide pins – due to corrosion or misalignment – resulting in Un-even pad wear and rotor cracking
Damaged boots and seals – corroded and seized internals
Misapplicated vehicle – reduced pad and rotor life.

9. Known Field Issues Premature / uneven lining wear Low parking forces
Friction material performance did not meet application demands
Low parking forces
Required increased spring forces or additional spring chambers
Automatic adjuster performance not consistent
Requires specific ASA pistons
Binding of pistons and caliper slide mechanisms
Vibration, distortion and corrosion
Unbalanced chamber weight on caliper slide rails or pins
Rotor heat checking and cracking
Drum / disc compatibility
Friction materials
Disc brake hysteresis greater than drum brake
Brinelling of lining backing plate dovetails
Pad assembly drops down in contact with rotor.
Anti-rattle spring rivet cuts a grove in the edge of the rotor
Fracturing anti-rattle springs
Low grade stainless steel offers little corrosion protection
Premature / uneven lining wear
Friction material performance did not meet application demands
Low parking forces
Required increased spring forces or additional spring chambers
Automatic adjuster performance not consistent
Requires specific ASA pistons
– Green Piston for T20-24
- Blue Piston for T30-36 chambers
Binding of pistons and caliper slide mechanisms
Vibration, distortion and corrosion
– need to ensure slide pins are free of corrosion, debris or paint. Slide pins should be aligned correctly
Unbalanced chamber weight on caliper slide rails or pins
Rotor heat checking and cracking
Drum / disc compatibility
Friction materials
Disc brake hysteresis greater than drum brake
-Need to make sure vehicle air system is properly balanced
Brinelling of lining backing plate dovetails
Pad assembly drops down in contact with rotor.
Anti-rattle spring rivet cuts a grove in the edge of the rotor
-Result of unbalanced air system and/or front interlock pressure too high (suggest limit FILP pressure to 40 to 50 psi).
Fracturing anti-rattle springs
Low grade stainless steel offers little corrosion protection
-current production changed to include a magna coating for better corrosion protection.
-one customer complaining of issue.

10. Repercussions
Customer Dissatisfaction
Loss of confidence in Disc Brake Products
Many customers switching back to Cam Brakes
Most ADB Suppliers Exited Market Due to Technical Problems – Refocused NHTSA Efforts
ARM has received a lot of flak over the years due to ADB1560 performance problems.

11. Basic Inspection Available Lining Running Clearance Seized mechanism
Direct visual inspection (1/8” of slide pin visible inboard replace-see maintenance manual 4M)
Running Clearance
See maintenance manual 4M. In service free stroke 3/4” to 7/8”
Seized mechanism
The brake lever should be able to cycle by hand with the clevis detached and pads removed
Slide pins
The caliper should slide freely by hand with the pads removed
Refer to Maintenance manual

12. Rotor Inspection Cracked-Replace Heavy heat checks-Replace
Deep scores
Cracked-Replace
Heavy heat checks-Replace
Deep scores-Replace
Blued-OK-Find cause of high heat
Cracked
Heavy heat checks
Blued

13. Brake Pads Available Lining Mixes: R701 (standard)
PMI (alternative)
PMI 9000X253 (specialized)
For high parking requirement
Limited to aftermarket
Back in 2002 we were contacted by San Diego FD with parking issues. Needed to develop a material to improve parkign performance in High grade applications.

14. Pad inspection Permissible Replace Slight Surface Cracks
Slight Crumbling of edges
Slight gaps between lining and back plate. (<1mm)
Replace
Delaminated/De-bonded material
Major cracks in structure of material
Large missing segments

15. Serviceable Components
Chamber brackets
Actuator nuts
Bushings
Calipers
Disk brake caliper piston
Misc. Items-Piston return spring, piston boot, cap screws pressure relief fitting
O-Rings, snap rings, seals, washers
Pins
Powershafts
Powershaft cap assembly
Torque plates
Rotors
Hubs
Ref. Catalog PB-8857