Why ABA’s? Automatic Brake Adjusters are intended to provide efficient day-to-day service braking by maintaining optimum lining to drum clearance, which in turn ensures proper brake chamber stroke. However, different approaches by ABA manufacturers are sometimes used in accomplishing this goal. The Haldex ABA is a “clearance-sensing” brake adjuster which maintains a nominal distance or clearance between the lining and drum under a variety of braking conditions. Clearance-sensing adjusters are not subject to varying driver input or operational parameters.
New Installation 1. 1.Determine what axle the adjuster will be used on Determine the camshaft diameter & number of splines Determine the adjuster arm length Determine clevis pin diameter Ensure that chamber is installed in proper mounting position to match adjuster arm length Select the proper ABA kit. P/N S/N33489 Installation Indicator and Notch Arm Lengt h Camshaft Diameter Ask the right Questions!!
Installation Procedures Block wheels. Release spring and service brake. Air chamber push rod Must be Fully Released for proper adjuster installation and operation. To maintain a fully released parking brake, a minimum of 80 psi reservoir pressure must be maintained. If air pressure is not available the spring brake must be manually caged. Push rod must be Fully Released during installation.
Installation Procedures The slotted adjustment plate is mounted to the “S” cam support bracket. Adjustment plates for Rockwell/Meritor, Dana and Fruehauf axles require two bolts. Adjustment plates for Eaton axles require one bolt (see insert). Position plate on adjuster side of the “S” cam support bracket. Added plate thickness requires the use of longer mounting bolts.
Installation Procedures Apply anti-seize type lubricant to splines and install adjuster on camshaft with adjustment hex pointed away from air chamber. Secure brake adjuster to camshaft with snap ring. Install enough washers (per TMC recommended practice) to reduce the end play to less than.060 Correct (Brakes Released) Incorrect (Brakes Released)
Installation Procedures Rotate adjustment hex clockwise until adjuster arm enters clevis and holes line up. Do not pull push rod out to meet adjuster. Coat the clevis pin with anti-seize type lubricant and install clevis pin, then secure with a cotter pin.
Installation Procedures Rotate the control arm away from the adjustment hex (towards the air chamber) until it comes to an internal stop.
Installation Procedures With brakes released and the control arm rotated properly to an internal stop, the “Installation Indicator” should fall within the slotted area as shown here. Most Haldex adjusters are unhanded, and may be used on either side of the axle. Note: Some steer axles utilize an offset casting which requires a left and right hand adjuster.
Installation Procedures Insert the flat end of the anchor stud through the control arm bushing. Push the threaded end of the stud into the anchor plate slot. The shoulder adjacent to the threaded end of the stud must engage the slot properly to prevent the stud from rotating. Install the 11/16” flange head nut loosely.
Installation Procedures Position adjuster control arm so the installation indicator falls within the control cover slot. Tighten the 11/16” flange head nut, Ft. Lbs.. Check to make sure the control arm did not move out of position while tightening.
Installation Procedures After installation, the adjuster must be manually adjusted by rotating the adjuster hex clockwise until the lining lightly contacts the drum. Once lining-to-drum contact is achieved, rotate adjusting hex counter-clockwise ½ of a turn (1/2 turn should include any free-play). A minimum of 13 Ft. Lbs. is necessary to overcome the clutch. Ratcheting sound will occur during back off.
Final Inspection Ensure parking brake has remained fully released during installation. Check for proper installation of indicator (AA1 Adjuster only), snap ring and cotter pin. Check the application stroke of each brake assembly with the air supply system between psi. If stroke is within operating range for chamber size, no action is necessary. If stroke is too long or short, re-check adjuster for proper installation. Check for loose wheel bearings, binding camshafts, worn or missing shoe return springs, defective air chambers such as push rods binding or chambers inoperative. Check for cam bushing wear within the foundation brake and cam support wear or damage. Continuous “manual” adjustment of an Automatic Brake Adjuster may cause internal clutch damage and shorter service life.
Operational Check 2 Steps to Ensure Proper Adjuster Function 2 Steps to Ensure Proper Adjuster Function 1. 1.Rotate adjusting hex counterclockwise and check for minimum 13 ft.-lbs. torque (replace adjuster if less than 13 ft.-lbs. torque) Rotate adjusting hex counterclockwise one full turn to create excessive clearance. Install 7/16” wrench on adjusting hex and make several service brake applications. If operating properly the wrench will rotate clockwise at the end of each “release” stroke. The Haldex adjuster is designed to take up approximately 10% of the excessive clearance with each release. If the ABA is determined to be faulty, it should be replaced immediately. Do not operate as a manual brake adjuster.
Measuring “Free” Stroke Free stroke is the amount of movement of the adjuster arm required to move the brake shoes against the drum. With brakes released, measure from the face of the chamber to the center of the clevis pin “A”. Use a lever to move the adjuster until the shoes contact the drum “B”. The difference between the fully retracted, & drum contact measurement is the free stroke. Free stroke should fall between ⅜” & ¾”. Free Stroke = B minus A Stroke measurements taken from face of air chamber to center of clevis pin
Measuring “Applied” Stroke NOTE: New brake assemblies require a burnish period. During this time you may experience a longer stroke than normal. Vehicle must be operated and brake assemblies allowed to reach normal operating temperatures in order to achieve full burnish Drain the air supply system to between psi With spring brake released, and the service brake in the unapplied position, measure from the face of the brake chamber to the center of the clevis pin. Record this dimension Make a full service brake application and measure from the face of the brake chamber to the center of the clevis pin Record the difference between the two measurements. This is your “applied” stroke. If the free stroke is good, but the applied stroke is too long, there is likely a problem within the foundation brake system. Applied Stroke = C minus A Applied Stroke measurements taken from face of air chamber to center of clevis pin
NACVS A North American Commercial Vehicle Safety Alliance TypeAdjustment Limit ” ” ” ” ” 302” ” TypeAdjustment Limit 16L2” 20L2” 24L (early Design) 2” 24L (Late Design) 2.50” 30L2.50” Standard Clamp Type Brake Chamber Long Stroke Brake Chamber *The applied stroke of the brake should be checked per CVSA guidelines at psi reservoir pressure.
Service Intervals Adjuster Type Manufacture Date Lubrication Interval Type of Lubricant Standard AdjusterPrior to June ,000 miles or every 3 months Standard Chassis Grease S-ABAAfter Jan. 2000Once a year Standard Chassis Grease Reduced Maintenance Adjuster After June 1996Once a year Standard Chassis Grease No-Lube ™ AdjusterAfter June 1996NoneSealed Unit 3+% Moly-disulfide & teflon grease should not be used or shortened service life may result.