If you’re thinking about driving a truck for a living you’ve probably noticed that those big rigs all run with air brakes.
Now, if you’ve ever wondered why these trucks use air instead of hydraulic for their brakes, here are a few reasons why.
Those things are simply a lot more reliable and also a whole hella of a lot stronger.
As you know, big ass trucks are huge and usually carry a lot of weight. Trucks carrying concrete, garbage, passengers and tree service company trucks carrying around a bunch of tree trimming can carry a whole lot of weight. All of this weight needs a whole lot stronger braking system.
Air brakes work pretty much the same way as hydraulic brakes do but without the hydraulic fluid. There is nothing but air in the lines. When you press on the brakes in your car, you send hydraulic fluid through the system in your car that applies pressure to either the brake pads that squeeze the disc on the wheels or spread out the pads inside the drums in the wheels.
Well, the same is true with a truck’s air brakes. The only thing is that trucks only use drums for brakes and they are huge compared to even the biggest pickup. So with air being in the lines instead of fluid creates more power to apply the pressure.
Inside a big rig, however, is an air compressor very much like the compressor you’d see at a gas station to fill up your tires with air. A truck has that built into the truck and also has two air takes to store the air it produces. The truck will constantly keep these air tanks filled with air to always have a steady supply of air needed to apply air pressure.
Understanding air brakes are one of the biggest reasons people need to educate themselves to have a CDL, or commercial drivers license. They need to understand how they work and how to know when they are not working properly.
Checking Air Brakes
There are some simple tests anyone can do to check and make sure air brakes are working properly.
The very first one is to make sure the air takes and the entire air brake system does not have any leaks. This is done by simply applying pressure onto the brake pedal. There should be two air take gauges on the dash of the truck, even on old trucks built in the 80s will have these gauges.
Check to see if the needles displaying the amount of PSI in the takes drops at all as you press on the brakes for 30 seconds. If it drops at all, you got a leak. If you don’t see it drop, you’re golden.
Another test is checking the compressor and make sure it works. The cool thing about this test is that it checks and tests two components of the air brake systems.
For this, simply tap on the brakes over and over again to drain the air out of the takes it has. Watch the gauges and you’ll see them slowly drop off. Keep doing this until the gauges reach about 50 PSI. At this point, this check the emergency air brake alarm system on the truck. All truck signal an alarm once the air pressure in the air tanks reaches around 50 PSI. This is done to make sure the driver is aware of the low pressure.
Once the air pressure gets that low and the air compressor in the truck kicks in and starts to fill the tanks as quickly as possible. If you see the needles in the gauges start to go up, you’re golden. This means the compressor is working just fine.
The final test is checking the parking brake. The parking brake on a big rig is extremely powerful. It is held down by huge springs and air pressure. When a driver truck pulls the yellow knob on the dash for the brake, it releases the air pressure on the springs to engage the brake. Yet, another reason truck uses air brakes.
All trucks come equipped with a system to release the parking brake on its own. Once the pressure in the air tanks reaches 30 PSI and below, the parking brake will engage on its own. This is by design.
The reason is just in case the air brake system is malfunctioning, has a leak, or just is not working, the truck will not be able to move. No one wants a big rig on the road with bad brakes. That is why all trucks are designed this way.
So there you have it.
A quick rundown as to why trucks use air brakes.