Truck Parts and Service | Heavy Duty Trucking, Aftermarket, Service Info
Issue link: http://read.dmtmag.com/i/376303
12 Tech Updates B endix has released a step-by-step guide for replacing air disc brake friction material as part of its Tech Tips series. Pads on air disc brakes are the same whether they are equipped on a steer, drive, or trailer axle, Bendix says. The steps required to replace each wheel end are listed below. Release or cage the parking brake so the axle rotates freely, then remove the wheel. Once the wheel end is visible, fi nd and remove the cap covering the shear adapter of the brake caliper. Using a 10 mm socket wrench or a ratcheting box wrench on the adapter, turn the adjuster counterclockwise – a clicking noise indicates that the tappets are "backing off," or loosening the pads' grip on the brake rotor – until it stops. A chain connects the pair of tappets to extend and retract them simultane- ously. Once the shear adapter is fully backed off, the brake pads can be freed for removal. A retaining bar across the top of the brake pads holds them in place. Use a small pair of pliers to remove the spring clip from the pin fasten- ing the retaining bar, then remove the washer from the pin as well. Push down on the retaining bar, pull out the pin, and remove the pad retaining bar. The two brake pads can now be lifted out from either side of the rotor. Take a quick look at the pads. The minimum friction thickness is about 2 mm – roughly the thickness of a nickel. Compare that with the thick- ness of new pads to see just how much usage you get out of air disc brake friction. Before installing the new pads, take some time for a preventive mainte- nance inspection: O Using the shear adapter, extend the tappets and inspect the tappet boots to make sure they are not damaged or contaminated with dirt, which can cause them to bind. O Inspect the guide pin boots: Push the caliper all the way inboard to open up the boots and check them for damage and contamination. O Look over the tappets, seals, and bushings. If components are damaged they must be serviced. Use the brake manufac- turer's service data sheet to determine the right kit, which should include the components as well as any special tools to ensure that new bushings are set at the proper depth. Note that slide pin lubrication is not required. Air disc brakes are lubricated for life and do not need grease fi ttings or oil spray as long as the components remain uncontaminated. When the inspection is complete, make sure the tappets are fully backed off so they are fl ush, and slide the new brake pads down into position. They will go in only one way, with the friction facing the rotor and the pad springs at the top. Once the new friction is installed, re- place the pad retaining bar and fasten it in place with the pin, washer, and clip found in the replacement service kit. With the 10 mm socket wrench or ratcheting box wrench, turn the shear adapter clockwise to adjust the tap- pets until the new pads make enough contact with the rotor to stop it from free-wheeling, then back it off – coun- terclockwise – three clicks. Replace the cap that covers the shear adapter, and the pad replacement is complete. T R U C K P A R T S & S E R V I C E | S e p t e m b e r 2 0 1 4 SAFETY RECALLS The following are safety recalls issued by the National Highway Traffi c Safety Administration: Daimler Trucks North America is recalling certain model year 2015 Freightliner Cascadia, 122SD, and Business Class M2 trucks manufac- tured March 20, 2014, through April 10, 2014. Due to an axle manufacturing error, there may be weak spots in the beam of the affected axle assemblies. The axle weak spots could cause the axle beam to bend or cause wheel separation, increasing the risk of a crash. Spartan Motors Chassis, Inc. is recalling certain model year 2013-2014 Gladiator emergency vehicles manufactured Oct. 22, 2012, to Feb. 12, 2014. In the affected vehicles, a high pressure fuel fi tting may make contact with the aluminum engine tunnel overlay causing the fi tting to wear and possibly leak fuel. If the fuel fi tting leaks in the presence of an ignition source, there is an increased risk of fi re. Volvo Trucks of North America is recall- ing certain model year 2011-2015 VNL and 2014-2015 VNM trucks manufactured Nov. 17, 2010, through Feb. 5, 2014, and equipped with enhanced cruise control and without side fairings. In the affected vehicles, the active braking component of the enhanced cruise control can become disabled. If the active braking feature becomes disabled, the vehicle may not automatically activate the brakes as intended when the enhanced cruise control system is in use, thereby increasing the risk of a crash. FRICTION REPLACEMENT TIPS