Why should you use chocks when parking a trailer without spring brakes?
Answer: Newer trailers have spring brakes just like trucks and truck tractors. However, converter dollies and trailers built before 1975 are not required to have spring brakes. Those that do not have spring brakes have emergency brakes, which work from the air stored in the trailer air tank. The emergency brakes come on whenever air pressure in the emergency line is lost. These trailers have no parking brake. The emergency brakes come on whenever the air supply knob is pulled out or the trailer is disconnected. A major leak in the emergency line will cause the tractor protection valve to close and the trailer emergency brakes to come on. But the brakes will hold only as long as there is air pressure in the trailer air tank. Eventually, the air will leak away and then there will be no brakes. Therefore, it is very important for safety that you use wheel chocks when you park trailers without spring brakes..
Learn More :
- Compared with a straight truck or bus, there are ___ things to inspect in combination vehicles
- The service line
- You should not back a tractor under a trailer until the whole air system is
- You are coupling a tractor to a semi-trailer. You have connected the air lines. Before backing under the trailer, you should
- For coupling to be completed, the safety catch for the fifth wheel locking lever must be
- The trailer hand valve works the trailer brakes. Which of these statements is true?
- You should not use the trailer hand valve while driving because
- What is the emergency air line?
- After the trailer has been coupled to the tractor, the tractor protection control valve should be placed in what position?
- You supply air to the trailer tanks by
- Glad hands are used to connect the
- Under good driving conditions, you should leave at least one second of space between your vehicle and the vehicle ahead for every ___ feet of your vehicle's length
- After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by
- You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and
- A trailer is most likely to jackknife when it is
- The front trailer supports are up, and the trailer is resting on the tractor. Make sure that
- Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is ___; the service line is ___.
- While you are driving, your emergency air line breaks or gets pulled apart. The loss of pressure will cause the
- Describe what the trailer air supply controls does
- If the brakes did not release when you pushed the trailer air supply valve, you should
- You have a major leak in the service line, and you apply the brakes. Service air pressure will escape and cause the
- After connecting the air lines but before backing under the trailer, you should
- What is the emergency air line for?
- Which of the following is true about off-tracking or "cheating?"
- In general, the higher your truck's center of gravity, the
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