System PartsQuestion 7 of 60
Spring brakes on a truck are held in the released position by what?
a.Air pressure
b.Hydraulic fluid
c.Engine vacuum
d.Electrical current
Explanation
Spring brakes use powerful springs to apply the brakes, and air pressure holds those springs back so the brakes stay released while driving. If air pressure is lost, the springs push the brakes on automatically. This provides an automatic safety braking feature when air is lost.
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- What happens to the spring brakes when air pressure drops to a very low level (for example, 20 to 45 psi)?
- Why do heavy vehicles use a dual air brake system?
- In a dual air brake system, before driving you should let air pressure build to at least what level in both systems?
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