Camshaft bushings should be changed every time a brake reline is performed. 12. 13. Excessive spline wear between the cam shaft and slack adjuster will limit push rod travel.

When Should S-cam bushings be replaced?

If the radial play is 0.030 of an inch or more, the cam bushing or camshaft is worn and needs to be replaced.

How often should you grease S cams?

All S-cam tubes should be lubricated at 25,000 mile, re- gardless of brake brand. Fully lubricated brake S-cam tubes ensure that moisture and contaminants do not enter the cam tube, potentially causing corrosion, slow return, and seal damage.

What is a cam bushing?

All components of a foundation brake system, including brake camshafts and bushings, are very important components for the safe operation of commercial motor vehicles. Camshaft bushings provide support and flexibility in the proper operation of a vehicle's braking system.

What does the S-cam do?

The principle of the S-cam allows the brakes of big vehicles to be more compact and less moving parts, since it only relies on a rotating shaft. Generally speaking, a tractor trailer requires more brakes than a typical vehicle, so making the brakes as simple and as cost effective as possible is very important.

Replacing S-Cams And Bushings

How often should slack adjusters be checked?

Every three months or 25,000 miles: Check the condition of the foundation brakes, including drums, shoes, linings, cams, rollers, bushing, etc.

How often should slack adjusters be greased?

It should easily take less than a minute per adjuster,” Gilboy said. “Bendix recommends greasing with an NGLI grade-2 lubricant every 30,000 miles, but you can also make things less complicated by greasing the ASAs every time you do a preventive maintenance inspection.”

How often should Semi U joints be greased?

Improper lubrication: Some u-joints need regular maintenance. In most cases, you have to grease your u-joints every 5,000 miles or so.

Which statement is false about the S-cam brake?

1. False. Some S-CAM brakes have automatic self adjusters. These do need to be checked periodically for shoe drag due to other failures.

How much play is allowed in a slack adjuster?

Use a tool such as a small pry bar to move the slack adjuster and check the brake's free play — how far the center of the large clevis pin moves before the brake shoes come in contact with the drum. Free play should be between 3/8 and 5/8 of an inch.

Is there a left and right S-cam?

To ensure you've got the correct camshaft, turn the S groove to face you. If the Left hand will fit in the groove, you're holding a left hand camshaft. If replacing a camshaft on the passenger side, you'll replace it with a Right Hand Camshaft.

How do you check slack adjusters on free play?

To check the free play of manual slack adjusters of S-cam brakes, you should park on: A Level ground, chock the wheels and release the parking brakes. Check Slack Adjusters on S-cam Brakes. Park on level ground and chock the wheels to prevent the vehicle from moving.

How long do slack adjusters last?

Slack adjusters have a finite life expectancy – they do not last the life of the vehicle.” Depending on application, slack adjusters will need to be replaced after four or five years of use, Gary added.

How can you check slack adjusters?

3. How can you check the slack adjuster?

1. Park on level ground, turn off parking brakes, pull hard on each slack adjuster. It shouldn't move more than one inch.
2. Park on level ground, turn off parking brake and press brake pedal.
3. Park on an incline and see if the vehicle rolls.

Can you manually adjust automatic slack adjusters?

Proper maintenance of automatic slack adjusters also means no manual adjustments. “The only times that an automatic brake adjuster needs to be adjusted is during a foundation brake repair or initial setup,” Forbes said.

How often do you adjust slack adjusters?

It adjusts and takes up the slack in the stroke as the friction surfaces wear away. In a “normal” U.S. highway environment a manual slack adjuster would probably need adjustment approximately every 10,000 miles.

Why is it called S-cam brakes?

S-cam brakes:

Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake cam shaft. This turns the S-cam (named because it is shaped like the letter S). The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum.

How do you identify S cams?

To determine your S-Cam Length, measure your s-cam lengthwise from the inside of the s-head to the snap-ring groove at the end, past the spline.
...
For example:

1. C1311A-L = s-cam length of 11-1/32″
2. C1224A-L = s-cam length of 24″ through 24-3/8″
3. C1126A-R = s-cam length of 26-1/4″ through 26-1/2″

Where are S-cam brakes located?

The “S” shape on one end of the camshaft forces the brake shoes apart and against the brake drum. Many of the parts of an “S” cam brake are located in the wheel. Characteristic of the “S” cam brake design is the exposed pushrod. This allows easy access to the brake linkage to check adjustment.