UniDrive Test

When adjusting the manual slack adjusters, you should confirm correct wrench rotation by...

The push rod starts to pull out of the brake chamber
The push rod should move into the brake chamber
It does not matter which way the wrench is turned
The s-cam should rotate in the same direction as the brake application

What is not one of the procedure for triggering slack adjusters?

Add two additional brake applications after a five second delay
Apply and release no more than two full brake applications on one second intervals
Air pressure above 100 psi
Spring brakes released and brake drums cool

What do engine retarders essentially do?

Slows the engine rpm down
Speeds up the engine rpm
None of the above
Change the exhaust valve timing, essentially turning the engine into an air compressor

On all automatic slack adjusters, the brake is being tightened correctly if...

There is free play
There is no movement of the s-cam
The wrench is turning the s-cam shaft in the same direction as the brake application
The wrench is turning the s-cam shaft in the opposite direction as the brake application

Why should you inspect the rotors of air disc brakes often?

Cracks hiding behind the brake pads and backing plate will eventually become visible
None of the above
It's part of the pre-trip inspection procedures
Rust forms on the discs quickly

When adjusting manual slack adjusters, how much should be backed off?

1/3 turn
1/8 turn
1/4 turn
1/2 turn

When should you adjust automatic slack adjusters?

You never adjust them
Regular maintenance
During the post-trip inspection
During the pre-trip inspection

When adjusting manual slack adjusters, how far do you need to depress the lock sleeve?

Completely
50%
75%
25%

With the s-cam brakes incorrectly adjusted and applied, which statement is false?

Brakes out of adjustment will be using the lower half of available push rod stroke
The application is more than half of the available stroke
With increased lining to drum clearance, the push-rod stroke moves less
With increased lining to drum clearance, the push-rod stroke is longer

Which is the only automatic slack adjuster that uses brake application stroke for adjustments?

Arvin Meritor
Bendix
Haldex
Crewson Industries

With s-cam brakes correctly adjusted and applied, which statement is false?

Properly adjusted brakes will be using the upper half of available push rod stroke
Application with a cool drum is less than half of the available stroke
Correct adjustment provides a minimum of push-rod stroke before the lining touches the drum
Correct adjustment provides the maximum push-rod stroke before the lining touches the drum

When braking with a bobtailed tractor, where does the weight shift to?

The rear of the vehicle
The passenger side
The driver's side
The steering wheels

What happens if brake stroke indicators are missing?

They can be left off since they are not required
They must be retrofitted if missing
At some point they should be added
The truck is deemed to be out of service immediately

If the slack adjuster has a square adjusting bolt, what size wrench do you use?

5/16 open end wrench
7/16 open end wrench
7/16 box end wrench
5/16 box end wrench

What is the optimum re-adjustment guideline to slack adjusters?

1/4 inch (7 mm)
3/4 inch (19 mm)
1/2 inch (13 mm)
3/8 inch (9.5 mm)

If the slack adjuster has a hexagonal adjuster, what size wrench do you use?

5/16 open end wrench
7/16 box end wrench
5/16 box end wrench
7/16 open end wrench

Which will not assist drivers to brake smoothly?

Ensure the following distance is at the minimum distance and no more
Ensure the load is balanced
Ensure brakes are correctly adjusted
Ensure the tires are in good condition

Why should you ease off the brake just before stopping?

It uses up less air
To save wear on the brakes
To prevent jerking back
No reason

When preparing the vehicle for checking the brake adjustment, what range should the air pressure be?

Low pressure
High pressure
Operating range
It does not matter

When checking brake adjustment using the applied stroke method, which statement is false?

Have another person hold a full-service brake application, or use a device to hold the brake pedal down
Measure the distance the mark has traveled from the face of the brake chamber
Mark the push rod where it exits the brake chamber
Make a series of brake applications to reduce system air pressure to 50 psi

What do auxiliary retarders do?

They help to control speed on downgrades and preserve the service brakes for emergency stopping
They replace the park brakes
They replace the service brakes
None of the above

What is referred to as bobtailing?

Operating a tractor without a trailer
Having one trailer without a load
None of the above
Having two trailers without a load

Arvin Meritor slack adjusters are recognized by what?

It has a round adjusting head on the front end of the self adjusting mechanism
You can't
The name is stamped on the side of the unit
The square adjusting head on the end of the self adjusting mechanism

What is the purpose of a brake drum?

To keep the brake shoes together
To reduce lining wear
It dissipates heat into the atmosphere
To assist in helping stop the vehicle

To safely operate a bobtailed tractor, which statement is false?

Avoid using auxiliary retarders at their powerful settings
Reduce speed when road conditions are slippery
Avoid excessive acceleration and heavy brake applications
Drive below the speed limit on dry roads

Adjusting the manual slack adjusters incorrectly, what would the results be?

May cause a longer braking distance
None of the above
A complete replacement of the system
May result in no service or park brakes

Other than the Arvin Meritor, how much of an adjustment is with other slack adjusters?

1/2
5/8
7/16
3/4

What is the optimum free stroke measurement to slack adjusters?

3/4 inch (19 mm)
1/2 inch (13 mm)
3/8 inch (9.5 mm)
1/4 inch (7 mm)

What is a major disadvantage of removing the trailer from the tractor?

It increases fuel consumption
It significantly reduces the traction of the drive axels
More difficult to steer
It causes the nose of the tractor to lift up, causing a drag

When brakes are adjusted incorrectly, which statement is incorrect?

Eventually, the chamber can bottom out
Cast iron drums expand when heated
Push rods push less distance
It can create a total loss of brakes and a runaway

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