10 Important Facts About Bus Brakes

Before heading off on your bus adventure, there are only a few things more important to consider than the condition of your braking system. To do that, first, you need to understand the difference between brakes on your bus and your typical vehicle.

1. Air Brake Systems

Buses use Air Brake Systems, rather than hydraulic systems as found in other vehicles. Using compressed air to make the brakes work, the heart of this braking system is the compressor. Often directly attached to the engine, it can also be found engine mounted or belt-driven. Essentially, it turns every time the engine does and is fed oil directly from the engine’s pressurized oil system.

You will find there are air reservoirs positioned in several locations and plumbed together with one-way check valves. These store the pressurized air in readiness to draw from when required in the brake chambers.

bus air brake

2. Low-Pressure Warning Signals

Your bus will have a low air pressure warning signal. This consists of a warning signal that will come on to alert you before the air pressure in the tanks falls below 60 psi.

3. All Buses Must-Have Emergency Brakes

All buses using hydraulic brake systems must be equipped with emergency brakes and parking brakes. These are required to be fixed by a mechanical force and typically use spring brakes. If the air pressure is removed, the springs apply the braking system. You will see there is a parking brake system in the cab of the bus that allows the driver to let the air out of the spring brakes and enables the springs to put the brakes on. Alternatively, if there is a leak in the air brake system causing a loss of air, this will also cause the springs to apply the brakes.

4. Stop Light Switch

Obviously, it is vital to ensure drivers of vehicles traveling behind your bus are aware of your intended movements. They must be warned when you apply your brakes. The air brake system has an electric switch that turns on via air pressure, ensuring the brake lights go on when you step on the brakes.

5. What’s That Hissing Sound?

Ever noticed that weird hissing sound that buses make when it pulls up? Bet you have sat at a bus stop one time or another thinking, ‘Why do buses make that noise?’. Well, I hate to break it to you (pardon the pun), but that annoying hissing sound happens because instead of the braking system using fluid like a car does, the bus system uses compressed air to activate the system. There you go, mystery solved!

6. What Makes Air Brake Superior?

Air brake systems are preferable to hydraulic brakes for several reasons. Firstly, the air brake systems can tolerate small leaks. Importantly, the parking brake system also ensures a fail-safe emergency braking system, although it is true to say that some hydraulic systems accommodate for this also. If you are traveling across mountainous areas, you will find that hydraulic brakes may just not cope and become overstressed, whereas air-brakes can withstand this pressure in a much more robust way.

7. Coming to a Normal Stop

When approaching your typical course of stopping your bus, simply push the brake pedal down. Focus on controlling the pressure so the bus comes to a smooth and naturally safe stop. It is likely you may have a manual transmission, especially with many of the older cruising buses so if this is the case, it is important not to push the clutch until the engine RPM is down at almost an idle. As soon as you are stopped, select a starting gear.

8. Emergency Stops

Naturally, if a vehicle suddenly pulls out in front of you or an animal or other object appears on the road ahead, your human reaction is to slam down on the brakes. While this may be an adequate response if there is plenty of room to slow the bus and come to a stop, there are some safety factors to consider. There are two types of emergency stopping methods, the controlled braking or stab braking.

In controlled braking, the idea is to apply the brakes hard, keeping steering wheel movements very small. If the wheels lock or you need to make a larger steering adjustment, release the brakes then reapply as soon as you can. Stab braking sees you apply the brakes all the way then release when the wheels lock up. Immediately as the wheels start rolling, hit those brakes again.

9. Anti-Lock Braking Systems

In newer or modified buses, you may find you have an Anti-Lock Braking Systems (ABS) braking system. This will help you avoid wheel lock-up as it engages a computer system that anticipates a possible wheel lock, reducing braking pressure. In this case, there is no need to pump the brakes to stop the vehicle


10. Check your brake system regularly

It is naturally pretty important you get into the routine of measuring and adjusting your brakes. You may be surprised that is fairly easy and quick, so make sure you put it on your list of must-dos as you are cruising in your bus. You will note “Brake Check Area” signs often found on roadsides and typically at the top of the biggest hills in mountainous areas. When you have a whole lot of weight behind you, it's a pretty good idea to be certain you have the power to go downhill safely.

To drive certain types of heavy vehicles such as a bus, you must apply for the proper endorsements only if you plan to operate your bus as a commercial business. Otherwise if you convert it to an RV and are using it for private use, you don't need a CDL. However, it doesn't hurt to get the proper endorsements more so to educate yourself on how you should operate a large vehicle with air brakes. If you do decide to get your endorsements from the DMV you will need to learn the material contained in the DMV’s CDL Air Brakes section of the study manual. To be eligible for the air brake testing, you should learn and study about how air is maintained in the system and the pressure conditions required to drive under.

Note: Always check with the DMV in your state as rules and regulations change constantly.

This article was submitted by Nadeem Ghori who is the Content Manager and Web Developer at Webplex Inc with over ten years of professional experience. He's an expert in e-learning and online course generation.

 

 

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