[TITLE: WHAT IS BRAKE FADE TO PASS YOUR CDL AIR BRAKES COURSE]
Hi there, Rick with Smart Drive Test talking to you today about air brakes. In the last
thirty years
air brakes have become more or less bullet proof. The reason I say that is because
we put them on vehicles that carry our most precious cargo... school buses. You
will not find a school bus manufactured in the last five years that is not
equipped with air brakes. There all equipped with air brakes and if air
brakes were unreliable, there's no way we would be putting them on school
buses. So air brakes are reliable, however they have one weakness left. That
weaknesses is brake fade. We'll be right back. We're going to talk to you today about brake
fade.
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Hi there, Rick, welcome back.Talking you today about brake fade. Brake fade is when you overheat
the brake drums and they expand away from the shoes. The way that brake drums
work is is that there is a shoe inside of the drum. When you push down on the
brake pedal—whether a hydraulic system or an air brake system—it forces the shoe out
against the drum, creates friction, drag and brings the vehicle to a stop. In the
process of pushing the shoes out against the drum, you create heat. Often times
there's enough time lapse between the brake applications that that heat is dissipated
into the atmosphere, the same way that an air-cooled engine has fins on the
side of the engine and the air passes over those fins and pulls that heat into
the atmosphere.
Brake drums work the same. The air passes over the drum, over the rim,
and the heat is dissipated into the atmosphere. Now if you hold the brakes down too
much on a heavy downhill, a big downhill rather, with a heavy load, you
hold the brakes on all the way down you potentially heat them up too much where
the heat cannot be dissipated into the atmosphere, the drum expands away from
the shoes and no matter how hard you push down that brake pedal those shoes
are not going to come in contact with the drum. It's called brake fade. If you put
enough heat to the brake drum it can catch on fire and so too can the tire.
Now, one of the other things that's beginning to combat this is disc brakes. They are
beginning to make inroads into the industry but the technology's just not
quite there yet.
The benefit of disc brakes is that they do not experience brake fade, and this is
why we find them on high-end sports cars and motorcycles. Because when you heat
them up, the
rotor heats up and expands into the brake pads, not away from them. So
therefore disc brakes work better when they're heated up and do not experience
brake fade.
In conclusion, brake fade is the last weakness of the air brake system. If you
put too much pressure to the brakes you're going to heat them up. If you heat
them up, no matter how hard you push on that brake pedal the shoes are not going
to come in contact with the drum. Brake fade—it is required for an air brake
endorsement and it is much more important when you're doing heavy
downhill braking in British Columbia, West Virginia, and other places in North
America that have big hills. So keep it in mind and know the dangers of brake fade.
And when I advocate for downhill braking, is short, hard, intermittent
brake applications - don't hold the brakes on for very long. You wanna have them off
long enough that the air passes over the drums and is allowed to dissipate that heat
into the atmosphere.
I'm Rick with Smart Drive Test: remember, pick the best answer, not necessarily the right
answer.
Have a great day. If you like the channel subscribe below,
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[CLOSING CREDITS & MUSIC]