AfterMarketNews Auto Care Pro AutoProJobs Auto-Video.com Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service

Inside The Bosch Xperience Mobile Technician Training

Robert Bosch LLC has been bringing technician training straight to the shop this year with its Bosch Xperience mobile tour, and when it rolled into The Swedish Solution in Orange Village, Ohio, a team of editors from Babcox Media had to check it out. In...

Read more...

Oklahoma Shops Organize To Join Auto Care Association

The auto shops in Tulsa, Okla., are organizing an effort to all join the Automotive Service Association in order to improve the overall service levels of the city. ABC Channel 8 in Tulsa, Okla., has the details: Randy Calley of Same Day Auto Repair...

Read more...

Service Adviser Pay Program Tips That Work

If you are looking to drive up your profits, you need to ensure you have service advisers that have the right attitude, aptitude and ethics. They will need to have the natural talent to sell, they will need to be well trained, and they will need to have...

Read more...

Mercedes-Benz: Installation guidelines for Smart Car front wheel bearing

The typical solution for replacing the front wheel hub on a 2008-‘13 Mercedes-Benz Smart Car is a front wheel hub assembly, including a front wheel hub and knuckle. However, with a wheel hub-only ­solution for the Mercedes Smart Car, like the one offered...

Read more...

Kia: Uncovering Unperformed Maintenance

While some vehicle problems will motivate the customer to make an appointment, an equal amount of Kia repair opportunities will be discovered as the vehicle is being serviced. If you’re not already doing so, always encourage your customers to keep...

Read more...

The Evolving Oil Change Market

The only constant in the oil change business is change itself, especially if you’re trying to maintain an inventory of engine oil for all makes and models of vehicles. Since Volkswagen began ­requiring application-specific engine oil in the mid-1990s,...

Read more...

Tell Us Your Top 5 Tools and Win!

Send in your list of your five favorite tools and equipment that help you most in the shop, and you could be chosen to win a $25 gift card for Bass Pro Shops. From scan tools to flashlights, impact wrenches to on-car brake lathes or computer systems...

Read more...

Pulling Codes: Good Guys Vs. Bad Guys

The Story of U0100 This article will document Code U0100 — Lost Communication with the ECM/PCM. In the world of automotive module-to-module communication, it can mimic a good guy/bad guy situation — the good guy has made an attempt to communicate...

Read more...

Snap-on Franchisee Conference Introduces Latest Tool & Equipment Innovations

The Snap-on Tools Franchisee Conference (SFC), held in Orlando, FL, played host to more than 8,000 registered attendees this past weekend; including principals representing more than 3,000 North American routes as well as their families and guests. The...

Read more...

Diagnosing Power Steering Loss on a 2008 Ford Escape

The vehicle in question is a 2008 Ford Escape with a 3.0-L engine. The customer complaints are as follows: The steering wheel will turn by itself; at times, usually when turning, the vehicle will lose all power steering assist; and occasionally, while...

Read more...

Cartridge Oil Filter Tips

Cartridge oil filters account for a large number of oil filter applications in the field. The chances of improperly installing a cartridge oil filter are greater than with a spin-on filter. The key is to take your time, inspect before installing and follow...

Read more...

The Case of the Missing Starter

I was called last fall by a client who owns a heavy-duty diesel shop to diagnose a no-cranking condition on his father-in-law’s 2006 Chevrolet Tahoe. Because his work is mainly with heavy-duty trucks, my client knew he was lacking both in tooling and...

Read more...

Home Brakes Drum Brake Self Adjusters: Understanding These Ancient Devices

Print Print Email Email

d bridge bolts.

Opposing piston calipers are bolted to the knuckle and have pins to position the pads. Drum brakes have return springs to return the shoes to a rest position and hardware to hold the shoes to the backing plate. The shoes return to a fully retracted or rest position when the master cylinder releases pressure to the wheel cylinder. There is no compensation for lining wear.

In some cases, the master cylinder may contain residual check valves to prevent air from being drawn past the wheel cylinder cup seals when the shoes are retracted by the return springs. Before 1955, drum brakes required periodic adjustment. As the linings wore, the piston in the wheel cylinder would have to travel further to engage the shoe with the drum friction surface. The return springs would retract the wheel cylinder piston to its rest position. This caused the brake pedal to move closer to the floorboard when the brakes were applied. This was commonly referred to as low pedal.

Adjusting the brakes would move the shoes closer the drum friction surface and reduce the travel of the wheel cylinder piston. It also required more fluid in the wheel cylinder to apply the brakes. Adjustments were made by manually turning the notched wheel on the adjuster with a brake spoon for the self-energizing type.

The dual-servo drum brake with leading and trailing shoes requires a wrench to adjust the eccentric adjusting cams located on the backing plate. It took a good “sense of feel” to adjust the brakes evenly. The process was to tighten the adjuster or eccentric adjusting cam to a point where the shoes contact the drum friction surface and backing off the adjuster or eccentric adjusting cam to where the shoes just cleared the drum. It’s all in the “feel” as you turn the wheel and move the adjuster or eccentric cam.

Bendix/Wagner
The Bendix/Wagner self-energizing brake has a single anchor pin located above the wheel cylinder. The primary shoe is identified by its length and position on the shoe. The lining segment is shorter than the lining segment on the secondary shoe and is positioned toward the adjuster or heals of the shoe. When the brake is applied, the master cylinder applies hydraulic pressure to both wheel cylinder pistons.

The primary and secondary shoes engage the friction surface of the drum. The wrapping motion of the primary shoe transfers pressure through the adjusting screw and drives the secondary shoe against the anchor pin and friction surface of the drum.

The secondary wheel cylinder piston is held in its rest position as the secondary shoe is driven against the anchor pin.

The adjuster mechanism is attached to the secondary shoe. It is a mechanical device that is made up of the three components.

First, an adjusting screw that is a threaded device like a nut and bolt. The head of the bolt is a notched wheel with a cylindrical pin. A washer and slotted cap fits over the pin and engages web section of the secondary shoe. The nut is also a slotted cap that threads onto the bolt and engages the primary shoe.

Second, a lever moves on a pivot to engage and turn the notched wheel.

Third, a cable or linkage is attached to the lever and the anchor pin to move the lever at its pivot point. There are springs and retainers to hold the mechanism in place.

The adjustment takes place when the vehicle is in reverse and the brakes are applied or when the parking brake is engaged. The cable or link attached to the anchor pin pulls the lever mechanism based on the movement of the secondary shoe.

When the brakes are applied, the lever cannot move the adjuster screw because the brake pressure is being used to apply the shoes. The adjuster lever mechanism must store the adjustment and turn the notched wheel when the brake is released.

There are two types of Bendix/Wagner self-adjusters. Type 1 uses a cable attached to the anchor pin and hook that is attached to the adjusting lever. A guide holds the cable in place. A spring connects the lever to the primary shoe to contain the adjuster. Type 2 uses a cable attached to the anchor pin with a spring and guide that attaches to the lever.

Type 2 uses the same cable guide as Type 1. On Type 2, the lever is connected to the secondary shoe with a pin and return spring. A spring connects the primary and secondary shoe to contain the adjusting screw.

On the Delco Moraine type, the adjuster uses a lever assembly, linkage and adjusting screw. The lever assembly is made up of the adjusting lever with spring-loaded link. The linkage is attached to the anchor pin and spring-loaded link of the assembly. The lever is attached to the secondary shoe at the shoe hold down. A lever return spring is placed between the lever assembly and shoe. A spring connects the primary and secondary shoe to contain the adjuster.

Dual Servo
Dual Servo brakes use two primary shoes and two anchor pins. The pistons of the wheel cylinder apply both of the shoes. The adjuster is located under the wheel cylinder. The adjuster uses an adjusting screw and notched wheel and lever in the same way as the Bendix/Wagner. A lever is attached to one of the shoes to adjust the notched wheel. The lever is usually part of the parking brake assembly.

There is no pressure on the adjusting screw when the brakes are applied allowing the lever to turn the notched wheel. A return spring is used to contain the adjuster in the same manner as the Bendix/Wagner type. This is different from the Bendix/Wagner type where the adjustment takes place after the brake is released.

Adjuster Inspection
The lever and notched wheel are in contact and move against each other every time the secondary shoe moves off the anchor pin. A groove can be worn in the lever and the notched wheel will also wear. A grove worn in the lever can prevent the adjuster from working properly. The wear on the notched wheel can easily be determined when it is compared to a new adjusting screw. The cable can be stretched or frayed.

Springs and linkage can also become worn. Don’t forget that there are left and right adjusting screws. If you install one on the wrong side the lever, it will turn the screw the wrong way.

In a disc/drum application, the automatic adjusters play an important role in maintaining proper brake balance during the time when the shoes are seating to the drum. The linings on most premium replacement shoes are eccentrically ground to produce a clearance at the shoe’s heel and toe.

This allows for a closer drum-to-shoe clearance. As the brakes are applied, the center of the lining contacts the drum first. As hydraulic pressure increases, the shoe will flex allowing the lining to completely contact the drum friction surface. As the shoes wear in, there will be less flex in the shoe and it will closely fit the contour of the drum.

For the first 100 miles or more, the adjuster will be the most active and keep the brake pedal at its proper height. After the shoes have seated, the adjuster will turn the notched wheel in small increments. Replacing the adjusters can provide your customer with a repair that ensures proper brake applications and pedal height.

The following two tabs change content below.
Latest articles from our other sites:

AVI Releases New Live Stream 7 (LS-7) Event

Save This Date: On Wednesday, Sept. 10, Customer Service expert Bill Haas will teach a FREE live, online course called "Service Selling Skills – Close One More Job." In this course from Automotive...More

Philips Introduces New Anti-Counterfeit Xenon HID Packaging

Philips Automotive North America, a division of Royal Philips, has developed special packaging to prevent piracy and protect customers from buying counterfeit Philips Xenon HID lighting. The new packaging...More

Nissan Group sees 11 percent increase in July

Nissan Group announced total U.S. sales for July 2014 of 121,452 units, an increase of 11.4 percent over the prior-year and a July record. Nissan highlights: Nissan Division set a July record with...More

Fiat 500 six-speed automatic transmission available to try at Abarth Track Experience

With the addition of three new stops on the 2014 schedule, Fiat 500 Abarth owners will now have more opportunities to develop their driving skills in the one-day Abarth Track Experience. The Fiat...More

Snap-on Offers Top 14.2 Reasons To Upgrade To Latest Diagnostic Software Release

Keeping the diagnostic tools up-to-date is critical, because without the latest vehicle coverage, professional technicians simply cannot service as many vehicles in a day. Snap-on Software Upgrade 14.2...More

Tell Us Your Top 5 Tools and Win!

Send in your list of your five favorite tools and equipment that help you most in the shop, and you could be chosen to win a $25 gift card for Bass Pro Shops. From scan tools to flashlights, impact...More

Tips for identifying timing belt, tensioner and idler failure

Courtesy of SKF When identifying timing belt, tensioner and idler failure, the first sign of wear is noise. For example, if the tensioner sounds bad, it’s usually bad. Start by listening to hear...More

Diagnosing Power Steering Loss on a 2008 Ford Escape

The vehicle in question is a 2008 Ford Escape with a 3.0-L engine. The customer complaints are as follows: The steering wheel will turn by itself; at times, usually when turning, the vehicle will lose...More