CDL Air Brakes Course S. 5.1 | California State

Hi there smart drivers. Rick with Smart Drive Test talking to you
today about CDL air brakes in the state of California. I had a request from Josahandy that she wanted
me to go over the manual in the similar fashion that I had done for New York state. Josahandy a was working towards her CDL license
and wanted some more information about the airbrake portion of it and I do apologize
if Josahandy is a woman because Josahandy can be either female or male. Today what I’m going to do is, I’m going to
go through the manual for the state of California for CDL air brakes, which is chapter 5 and
go into the trailer section which is in chapter 6. And I’ll go over that and give you some more
clarification and some more information about air brakes. Just as a note – students find air brakes
challenging and there’s no doubt that air brakes are challenging. It’s a technical course. There’s lots of terminology that you have
to learn and some of the terminology you have to learn, it’s only for the purposes of the
license. Because California, New York state and all
the provinces in Canada are still teaching a forty-year-old air brake course. So unfortunately, there’s some stuff that
you just have to learn for the purpose of the license. A wig wag, for example, which haven’t been
on trucks or buses since the 1980s. Everything now for low air warning devices
is a light and buzzer. So, we’ll be right back to talk to you about
CDL air brakes in the state of California. [OPENING CREDITS & MUSIC] Hi there smart drivers. Rick with Smart Drive Test talking to you
today about CDL air brakes in the state of California. This is going to be a 4 video series: the
three sections in chapter 5 of the California CDL manual will be three separate videos and
then I’ll go into the trailering on chapter 6 and talk to you about trailers. Air brakes have been fitted on large commercial
vehicles since the 1920s. Air brakes were first on trains in the 1800s
to stop them. And during that period of time–almost a century
now that they’ve been on trucks and other commercial vehicles–they have proven reliable. Second, air brakes are able to transmit large
powerful forces– braking forces–over long distances. Think of a semi-truck, for example. The driver sitting at the front of the truck
and the trailer brakes are able to be put on 75 feet away. So large distances are able to be covered
with air brakes. Finally, air brakes are tolerant to significant
leaks in the system and will continue to operate normally. Unlike hydraulic brakes, where if you get
a leaking hydraulic brake fluid those brakes are not going to work. Fortunately there are fail-safes in place
for both for hydraulic brakes and air brakes that will allow them to work properly or at
least work and allow the driver to bring the vehicle to a complete stop safely and efficiently. So both air brakes and hydraulic brakes have
a fail-safe in them and we’ll talk about that in greater detail later in the video. No doubt, air brake courses are technical
and difficult to understand because the terminology that goes along with air brakes makes it difficult. We talk about service brakes, parking brakes,
and emergency brakes on an airbrake equipped vehicles. That for some, can cause confusion. Now the way to think about it is that the
brakes on an airbrake equipped vehicle are no different than the brakes on a car or light
truck. The car or like truck that you parked in your
driveway and you drive everyday, the brakes on an airbrake equipped vehicle are exactly
the same on your vehicle. When you go up and down the road, you push
down on the brake pedal, which are essentially the service brakes. The vehicle comes to a stop and the brakes
are released when you take your foot off the pedal. Essentially these are powered by hydraulic
fluid. The brake pedal is attached to the master
cylinder, which is essentially a pump. You push down on the pedal and create pressure
and the brakes apply and it comes to a stop. When you park the vehicle–for those that
use the parking brake when you park the vehicle–you apply the parking brake. The same thing on an airbrake equipped vehicle. You simply pull the buttons out on the dash
on a large commercial truck. Some buses you have to push it in because
it’s reverse. But if you’re driving a transit bus, you’ll
know that. However, for the purposes of this, we’re going
to pull them out and evacuate the air from the system. The large powerful springs expand and apply
the brakes and the vehicle is left parked indefinitely. On your vehicle, it’s a handle–either with
your hand or with your foot–you push down on it. It’s a ratchet system that locks into place
and is connected to the rear brakes via a cable. The vehicle has its brakes applied and the
vehicle is secure against movement indefinitely. If you’re going up and down the road and your
unfortunate enough to lose your brakes, you can use that lever and pull up on it and use
it as an emergency brake. Essentially what you’re doing is taking the
parking brake and applying the brakes using that for an emergency. Air brakes are exactly the same – in the event
of a catastrophic air loss in the vehicle, you lose enough air that those powerful springs
will expand and the spring brakes will come on. And we call them the emergency brakes So the
only difference between air brakes and the brakes that you find on your car or light
truck is the power source. For the service brakes on your car, or light
truck its hydraulic power or hydraulic force – push down on the brake pedal to activate
the pump and you apply the brakes. On a big truck its air. The parking brake on a car or light truck
– it’s simply mechanical power that comes out of you. You pull up on that ratchet… click click
click click click and it locks into place. On a big truck, it’s the large powerful springs…the
same thing on your car to use that parking brake as an emergency brake you simply pull
it up using mechanical force, and on a large commercial vehicle those large powerful springs–that
are usually used and best use for parking–are also the emergency brakes. In the state of California, when you show
up for your road test, you have to bring a vehicle that is equipped with air brakes. And in the state of California, they designate
air brakes as the vehicle having a low air warning device and having air gauges. If it doesn’t have those two components, then
you will have a restriction on your license. The restriction on your license will say “no
air brakes” and you won’t be able to operate a commercial vehicle that has air brakes. And in this day and age, it’s going to be
tough to find a commercial vehicle that doesn’t have air brakes. So you’re going to need air brakes in your
bid to get a job. Make sure you get your brakes – make sure
you bring the correct vehicle to your road test. You must have a low-air warning device and
must have air gauges. The air compressor on a large commercial vehicle
is exactly the same as the one you would find in a shop or garage. It pumps air into the tanks. When the tank pressure reaches a maximum,
the air compressor shuts off; when it goes to a minimum, the air compressor comes back
on and fill the tank up to maximum. On a large commercial vehicle, the air compressor
is either belt-driven or gear-driven. They’re not belt-driven anymore… they have
been belt driven since the nineteen seventies. They’re all bolted right to the side of the
motor and they’re gear driven. For the purpose of the license, you have to
know they’re belt driven. And if it is belt driven, the way you check
the tension on the belt is at the midpoint between the two pulleys, push down on the
belt. It should not go more than its own width. As well, the air compressor uses the engine
lubrication system, sometimes it’s cooling system–but I’ve never seen one that uses
the engine’s cooling system–most of them are air-cooled. As well, it draws air in from the engine’s
main filtration system. So the air compressor is truly parasitic. If it does have its own lubrication system–
which most likely it will not–you need to check it as part of your pre-trip inspection. The difference between an air compressor in
a shop and the one on your commercial vehicle is that the compressor runs the entire time
that the engine is on, so we need some way to control it. We control the compressor with the governor
and the governor puts it into the cut-out phase or the cut-in phase. In the cut-out phase, the compressor is pumping
air into the atmosphere and in the cut-in phase, its pumping air into the system. And the maximum pressure of the system is
around 125 pounds per square inch, which is the cut-out phase. And the cut-in phase–when it pumps air into
the system–is approximately a hundred pounds. When the system goes down to approximately
a hundred pounds, the governor will put the compressor into the cut-in phase. There’s a complete video on the governor – you
can find that here. Check out that for the complete details on
the governor. The air tanks–sometimes called reservoirs–store
compressed air. The air tanks are the first fail-safe in an
airbrake system. If the compressor stops working for some reason
or falls off the side of the engine, the air tanks hold enough air for 10 to 12 full brake
applications. On older systems, there will be three tanks:
1) the wet tank; 2)the primary tank; 3) and the secondary tank. On newer systems–the ADOS systems (Air Dryer
Integrated Systems)–they’re will only be two tanks – the primary and secondary tank. And how you know it’s an ADIS system is because
the governor will be located within close proximity to the air dryer. Air dryers have proven really good at ridding
compressed air of water and other contaminants. Therefore the air dryer has made the wet tank
redundant and no longer needed on these systems. Air tank drains: most of the air tank drains
on trucks are going to be manual. If you get low clearance vehicles–buses and
RVs and whatnot–they may be automatics, but for the most part they’re manual. The question on the test is: “how often do
you drain air tanks?” Daily, daily, daily – every day! That will be the question on the test. The reason for that is that water and other
contaminants collect in the tanks and you have to get rid of that. If there’s water in the tanks it could potentially
freeze and cause failure of the air brake systems, especially if you’re working in colder
climates – not so much California, but if you’re working in Alaska, that is definitely
a risk. That the water could freeze inside the airbrake
system and potentially cause it to fail. So daily, daily, daily, – drain the air tanks
on the system. The drains on the tanks can either be one
of two types: 1) a stopcock, which is just a tap that you open and allow the tank to
drain. 2) Most of them on big trucks have pull cords
and you pull the cord and hold it until the tank drains completely. It’s not likely you’re going to find alcohol
evaporators on an airbrake equipped vehicle in the state of California. Maybe in Duluth, Minnesota, maybe in Alaska,
but for the most part you’re not going to find them on vehicles in California. However, the alcohol evaporator introduces
methyl hydrate into the system and lowers the freezing point of water. So therefore, there’s less risk of it freezing
inside the system. Question on the test is: “what kind of methyl
hydrate do you put into the alcohol evaporator?” Answer: ‘manufacturer-approved methyl hydrate.’ If you want to think of another analogy, the
reason they put salt on the roads in the wintertime is to lower the freezing point of water. And this only works down to about -8°C (18°F),
so methyl hydrate inside an alcohol evaporator works the same, but like I said – in the state
of California, you’re not going to worry about one. And the answer to the question on the test
is “manufactured approved methyl hydrate is what you use to refill the alcohol evaporator. All tanks that are pressurized have a safety
valve on them. In the event that the pressure gets too high
and potentially could cause damage to the vehicle or danger to people in and around
the vehicle, the safety valve will let off the excess pressure. On an air brake equipped vehicle, it is set
150 pounds per square inch and you’ll know it’s the safety valve and that you have excess
pressure in the system because it makes a very distinct sound! The sound of a machine gun – if you hear that
sound & you look down at the air gauge and note that it’s around 150 pounds, which is
too high for an airbrake system because most of them run at a hundred twenty-five and a
maximum of 135–so you’ll see that it’s a hundred and fifty pounds. And when that happens, take it to a mechanic
and say authoritatively that the governor has failed. Maybe the compressor, but for the most part,
it’s usually the governor. Safety valve… hundred fifty pounds per square
inch. The brake pedal controls the service brakes. It can also be called the foot valve or the
treadle valve, but for our purposes we’re going to call it the brake pedal. The brake pedal controls the service brakes. You go up and down the road, you push down
on the brake pedal, it applies the brakes – the harder you push the harder of the brakes
apply. There is– on a large commercial vehicle that
has air brakes on it–a delay from the time that you put your foot on the brake pedal
to the time that the brake apply, and conversely when you release the brake to the time that
the brakes release. That is called brake lag and it’s a term that
you will need to know for the purpose of license. It’s a very slight delay–it’s less than half
a second, but there is brake lag in an airbrake equipped vehicle. As well, when you release the service brakes
on a large commercial vehicle, the air that you use to apply the brakes is exhausted into
the atmosphere. So if you pump those brakes, you’re going
to lower the air pressure in the system. And if you pump them hard enough – if you
fan them down or pump them hard enough, eventually what you’re going to do is lower the air pressure
in the system and it could get dangerously low, which you’ll know because the low air
warning will come on. And your brakes won’t work. So in a large commercial vehicle, especially
if you’re going downhill or are doing hard braking, don’t hold the brakes and then release
them, release and apply, release and apply. Hold the brakes down, so you have constant
pressure going to the brake chambers. That way you’re not going to lower the air
pressure inside the system. So don’t pump the brakes on a large commercial
vehicle. The foundation brakes: the foundation brakes
are the components of the airbrake system that actually bring the vehicle to stop. The brake drums, the linings, and the shoes
are all located on the axle and the tire and rim are mounted onto the drum. Inside the drum is the brake shoes and linings
and when you activate the brakes or push down on the brake pedal the shoes are forced out
against the drum. These create friction and slow the vehicle
and the tires. And if you have traction with the road, the
vehicle will come to a stop – at least that’s the hope and dream. The most common types of foundation brakes
are: ‘S’ cam brakes, wedge brakes, and disc brakes. Probably in this day and age, you’re not going
to find wedge brakes. Question on the test for wedge brakes is:
“how many brake chambers will wedge brakes have?” ‘may have one or two is the answer
to the question on the test. Disc brakes are beginning to make inroads
into the commercial driving industry and the reason for that is because disc brakes don’t
experience brake fade. And if you want the complete video on brake
fade, you can find that here. I’ll put a card up here for you, for the complete
video on brake fade. The ‘S’ cam brakes do experience brake fade. There’s heat generated from the friction,
because you convert forward motion of the vehicle into heat energy. That heat is dissipated into the atmosphere
via the drum and to some extent the rim. But if you put too much heat to the drum and
rim, eventually what’s going to happen is it’s going to catch fire and you’re going
to experience brake fade. Because it expands and moves away from the
brake shoes and the brake shoes will no longer come in contact with the drum. So brake fade is another term that you need
to know for the purposes of your CDL license test. And brake fade–not only for air brakes, but
any braking system is the one and only weakness that is left and driver error will cause brake
fade. So there’s no reason to experience brake fate. As well, downhill braking – you need to know
how to do that correctly. There’s a downhill braking video – I’ll put
up a card up here for you – for the complete video on downhill braking so you don’t experience
brake fade. “S’ cam brakes are the most common type of
foundation brakes. These are mostly found on semi trucks and
buses. As well, on a lot of newer buses you’re going
to find disc brakes but the ‘S’ cam brake, as you can see here in the image consists
of the brake chamber, the pushrod, the slack adjuster. And all slack adjusters are automatic, unlike
this image – it’s a manual slack adjuster. The ‘S’ cam and it goes into the brake shoes
and forces the brake shoes out against the drum. And you can see that there’s an ‘S’ on the
end of the ‘S’ cam, thus it’s called the ‘S’ cam because it’s shaped like an S and it basically
rotates when you apply the brakes and forces the shoes out against the drum. Friction is created and it and brings the
vehicle to a stop. The other type of brakes are CamLaster, and
the difference between ‘S’ cam brakes and CamLaster brakes is that CamLasters are self
adjusting and they also apply the brake shoes against the drum evenly. So on an ‘S’ cam, it forces the top out and
essentially there’s a bit of a lever there so the brakes don’t wear evenly. On a CamLaster, there’s some sort of slide
incline inside of the brake mechanism, which evenly pushes the shoes out against the drum. So the CamLaster is another type of foundation
brake that has advantages over the ‘S” cam type foundation brake. The other type of foundation brake is disc
brakes and disc brakes are beginning to make inroads into the commercial industry the reason
for that is because disc brakes don’t experience brake fade and you’ll find disc brakes on
most cars and light trucks now. Especially on high-end sports cars and motorcycles. And the reason for that is because when you
heat up disc brakes they actually work better than a conventional drum brakes. And the reason for that is because when you
heat up the rotor–the plate in the middle–it actually expands into the brake pads. So when you heat them up, disc brakes become
more aggressive. The problem on large commercial vehicles is
that there’s too much heat generated and when you have too much heat generated inside the
disc brakes the whole assembly kind of melts into a pile of goo and your vehicle careens
down the road. crashes into a tree and you die in a fire
inferno. So they’re coming, but they’re not quite there
yet! Because the materials aren’t there to absorb
the sheer amount of heat that is generated on large commercial vehicles. But you’ll see in the next 10 years that disc
brakes will become prolific within the commercial driving industry. Supply pressure gauges: all air brake systems
will have pressure gauges to tell you how much air pressure is in the system air pressure
gauges. There will be two pressure gauges inside the
system because there’s a primary and a secondary system. These haven’t been single circuit system since
the nineteen seventies. So all systems are going to be a primary and
a secondary system and you’ll either have two gauges–one for the primary system and
one for the secondary system–or you’ll have one gauge with two needles and one will be
green and systems You’ll need to operate the system above a hundred pounds per square inch
and also need to monitor maximum and minimum pressures as the system’s going up and down. This is to note that in fact, the governor
is working and putting the compressor into the cut-in phase or the cut-out phase. Application pressure gauge tells you how much
pressure you’re putting to the service brakes when you push down on the brake pedal. In the manual, it says that the harder you
push down on the brake pedal–if you’re going downhill and the brakes aren’t applying any
harder may indicate that you are experiencing brake fade or a other mechanical problems. Perhaps an air leak in the system and whatnot
– that’s not necessarily true. However if you are pushing down harder on
the brake pedal and the brakes don’t seem to be braking any harder and you are going
downhill or you have been using the brakes excessively could indicate that you have brake
fade. However the application pressure gauge is
really good for training students in terms of air brakes and pre trip inspection for
the purposes of a license. But going up and down the road – let’s really
hope that you’re not looking at the application pressure gauge while you’re going up and down
the road. Most normal brake applications are going to
be made at less than 10 pounds per square inch. If you’re making a harder brake application
than 10 pounds per square inch there could be something wrong with the airbrake system,
but for the most part it’s the application pressure gauge tells you how much pressure
you’re putting to the service brakes. The low pressure warning device is a buzzer
and a light on all modern vehicles. On some older vehicles you may find a wig
way which is essentially this little arm that drops down in front of your face when pressure
drops below 55 pounds per square inch. Wig wags haven’t been on vehicles since the
nineteen eighties. What happened was the pressure dropped in
the system a couple of times & this thing drop down in front of drivers. It scared the living daylights out of them,
they drove off the road, crashed into a tree and died in a fiery inferno. The engineers thought, “you know, maybe that’s
not such a great idea – let’s just go with a light & a buzzer. So a light and a buzzer in the state of California
must come on above 55 pounds per square inch. On a lot of vehicles, it’s going to come on
well above 55 pounds, as it says in the manual. On a lot of buses it’s going to come on between
80 & 85 – a lot of trucks it will do the same thing as well. Low air warning – all vehicles are equipped
with a low air warning and on modern vehicles they’re going to be a light and a buzzer. Stop light switch: which simply means that
when you push down on the brake pedal, the brake lights are going to come on. And as part of your pre-trip inspection, you
need to check the brake lights on a commercial vehicle when you’re doing your license and
every day as part of your pre-trip inspection. Stoplight switch – the brake lights come on
when you push down on the brake pedal. Front brake limiting valves: all vehicles
are equipped with automatic front wheel limiting valves and on newer vehicles you’re not going
to know that they’re there. However if you make a hard brake application
over 60 pounds– ok let’s hope that if you make a 60-pound brake application on an airbrake
system you got your seatbelt on because, if you make a 60-pound brake application, you’re
going to be doing a bug impression on the inside of the windshield. Let me tell you that vehicle is going to come
to a hard, hard stop. As I said, most normal braking is done at
less than 10 pounds per square inch on a vehicle equipped with air brakes. Automatic front wheel limiting valves reduce
braking to the front axles by 50% fore most normal braking because steer axles are used
for steering. And are not used for braking. However, over 60 pounds–as it says in the
manual–it’s going to come on equal to the rear brakes, but that’s a really hard brake
application. On older vehicles–if you’re driving something
1970s–it’s going to be a manual switch. It’s going to be on the dash, as you can see
here in the image, “slippery” “dry”. Most driving is going to be in the dry position. If it is raining or you’re on snow and ice
– put it into the slippery position to reduce braking to the front axles by fifty percent. Spring brakes: prior to the advent of spring
brakes a few semi-trailers got pushed over hill and killed a porta potty and engineers
and other officials thought, “you know, maybe we need some way of applying the brakes indefinitely!?!” So they came up with large powerful springs
to apply the brakes mechanically. Therefore, the brakes were applied indefinitely
while left parked. These large powerful springs inside the spring
brake chambers are piggybacked onto the service brake chambers They’re almost always on the
rear of vehicles because they also work as emergency brakes. Because the springs are held in the caged–in
the off position–with air pressure. If the air pressure drops too low–between
20 and 45 pounds–the springs will activate automatically, expand and apply the brakes. And we like to have the steer tires for steering,
so spring brakes are not on the steer tires – the steer axles rather. Rather they’re on the back of the vehicle. So they’re used for parking most of the time. And they’re also used for emergency brakes
in the event that the air pressure drops to low. And again, as it says in the manual, when
that low air pressure warning comes on, you’d better be looking for a safe place to get
that vehicle off the road and determine why you have an air leak. Also, question on the test is: “if the service
brakes are out of adjustment, the parking brakes are also out of adjustment.” So if the parking brakes are not working properly,
your service brakes are not going to be working as well. So you need to get them adjusted up. That’s the question on the test. If the service brakes are out of adjustment,
so too are the parking brakes and the emergency brakes. Parking brake controls is a four-sided yellow
button on the dash. Push it in to put air into the spring brake
chamber and cage the spring. This releases the parking brakes; pull it
back out to exhaust the air from the spring brake chamber and the spring expands and applies
the parking brakes. Also, if you lose air in the system, the spring
will expand and apply the parking brakes as an emergency brake. In the manual it says not to compound the
brakes. That’s what it’s called when you have the
parking brakes on and make a service brake application. All modern vehicles are equipped with an anti-compounding
valve, so you can apply the service brakes when the parking brakes are on & it just exhausts
the air into the atmosphere. Rather than putting air into the service brake
chamber when you compound the brakes. You’re making a service brake application
plus the pressure from the spring brakes could potentially damage the components inside the
system. So that’s what they’re talking about when
you apply the service brakes and the parking brakes at the same time – compounding the
brakes/ Modulating control valves: I’ve never seen a system that has a modulating control
valve. They’re out there somewhere. They’re in the manual and it allows you to
apply and release the spring brakes in a similar manner that you would do with the service
brakes. If your vehicle is equipped with that, there’s
a lever and there’s a locking mechanism on the lever, so that the parking brakes can
be held on. But modulating control valve allows the spring
brakes to be applied and released in the same way that you would with service brakes. Dual parking control valves: what they’re
talking about there is a separate air tank to release the spring brakes in the event
that you weren’t paying attention and sleeping, which you really shouldn’t be doing while
you’re driving. Anyway, the spring brakes applied and the
vehicle is stuck somewhere that is not desirable. There’s a separate air tank and there’s a
dead man switch on the dash. The dead man switch means that you gotta hold
it down in order to put air into the spring brake chamber and release the spring brakes. There’s a limited amount of air, so use it
wisely to release the spring brakes and move the vehicle to a safe location as quickly
as possible. Again, I’ve never seen this on an airbrake
system, so it’s unlikely that you’re going to encounter it. Most of these vehicles are going to have a
four-sided, yellow button on the dash to activate and release the parking brakes. And if you’re driving a semi truck, there
will be an eight-sided red octagon button that activates and releases the parking brakes
on the semi-trailer. So again, it’s a dead man switch – extra air
tank to release the spring brakes in the event that you weren’t paying attention and the
spring brakes activated in the event of a catastrophic air loss. All modern vehicles have ABS brakes & the
way that you know that the truck or bus has ABS brakes is when you turn the key to the
on position and wait momentarily the ABS light will come on on the dash– it’s usually orange–and
it will come on momentarily and then go off. That means that your ABS is working normally. If you’re not sure that you have ABS on your
truck or trailer, the way that you can tell is you go out to the unit. Locate the brake chamber – the airline that’s
running out to the brake chamber will have an electrical line zippy tied to it and that
is the way that you know you have ABS brakes on your vehicle. The way that you brake with an ABS system
– you brake normally in normal situations. It’s just going to have normal brakes on it
in normal braking situations; in hard emergency braking situations, it’s different than normal
brakes because what you do is you hold down on the brake pedal and hold hard and look
in the direction that you want to steer. Essentially ABS brakes stop the wheels from
locking up because when the wheels lock up, you lose steering and lose control of the
vehicle. So you hold the breaks down hard– shutter,
noise, pushback all of this is normal in ABS equipped vehicles. On older vehicles, the ABS light on the dash
may not go out until you obtain five miles per hour. After you obtain five miles an hour the ABS
light will go out. On trailers, oftentimes the ABS light is near
the rear of the trailer on the driver’s side. You can usually see it in the driver’s mirror. One of the things to keep in mind about ABS
brakes is that ABS brakes will not stop you in a shorter distance. ABS brakes are designed for you to keep control
and keep steering in the event of an emergency situation. So an emergency situation: hold the brake
down, hold it down hard. You may have to post off the steering wheel
and look in the direction that you want to go. That way the front wheels won’t lock up. Another component on your air brake equipped
vehicle might be a ATC –automatic traction control–automatic traction control diverts
power from a spinning wheel to another wheel on the rear axle so that you can regain traction. In some cases, it will actually cut power
to the motor. ATC uses all the same components as the ABS,
but simply tries to regain traction usually when you’re on slippery conditions in parking
lots and that sort of thing in the wintertime or in mud conditions where traction is compromised. So ATC uses the components of the ABS system
and piggybacks on that The other thing to keep in mind is if you got a combination vehicle–truck
and trailer–where one unit has ABS and the other unit doesn’t – this is particularly
prone to with trucks where you will have ABS and the trailer won’t, so if you’re in an
emergency situation with the truck and trailer, just keep an eye in the mirror because you
may be braking with ABS on the truck, but the trailer is actually normal brakes and
if you’re pushing down hard on the brake pedal – the trailer brakes are actually locked up. Make sure you’re having a look in the mirror
there because if the trailer starts coming around you’re going to have to release the
brakes to try and get that unit straightened out. Anti-lock braking systems are designed for
you to keep control of the vehicle and to keep steering. As I tell students all the time, the reason
that we lose control of the vehicle is because of over-braking, over-steering, and over-acceleration. Any one of those will cause the wheels to
lock up or to spin. And a spinning or locked wheel always leads,
which means that the back end is going to come around or the front end’s gonna kick
out. So over use of the primary controls is going
to cause you to lose control and a tractor-trailer unit could potentially cause you to jackknife. So keep your eye on the mirror and use the
ABS correctly. Review questions: turn the video off, answer
the questions -come back and we’ll go over the review questions together! First question, why must air tanks be drained? Air tanks must be drained to rid the system
of water and other contaminants in the system. Water in the system could potentially freeze
if its cold and cause the system to fail. Question on the test is how often do you drain
air tanks? Daily, daily, daily – everyday drain the air
tanks. What is the supply pressure gauge used for? The supply pressure gauge is to tell you how
much pressure is in the system. Question on the test: What do the air pressure
gauges tell you? They tell you how much pressure you have available
for a service brake application. For example, if you have 40 pounds in the
tank, the maximum brake application you can make is 40 pounds; if you have a hundred pounds
in the tank, the maximum brake application you can make is a hundred pounds. Next question: all vehicles with air brakes
are equipped with a low air warning device? TRUE. All airbrake equipped vehicles must have a
low air warning device and it will either be a wig wag or a light and a buzzer. In the old days they were wag wags but they
haven’t been since the nineteen eighties. It must come on above 55 pounds per square
inch. If it is a wig wag and it does come on – in
order to reset it–once the system pressure goes above 55psi–you just push it back up
above the visor there and it’ll stay up. What are spring brakes. Spring brakes on large commercial vehicles
equipped with air brakes are used for the purposes of parking and emergency brakes. When you’re going up and down the road, these
large powerful springs are held in the released or caged position by air pressure. if you lose air pressure in the system, the
springs will expand & apply the brakes and work as an emergency system to apply the brakes
and bring the vehicle to a stop. When you park, you pull the four-sided yellow
button out on the dash to exhaust the air from the spring brake chamber. The spring expands and applies the parking
brakes. The spring brakes are best used for parking
– that’s the question on the test. Front wheel brakes are good under all conditions? The answer oddly enough is true. Despite the technology that is applied to
the front steer axles to prevent lock up–ABS brakes, front wheel limiting valves, and the
fact that there aren’t spring brakes on the front steer axle–all of that would lead you
to believe that a front wheel lock up is dangerous. When in fact skid pad tests have shown that
rear wheel lock up is actually much more dangerous for the driver than steer axle lock up. Therefore, front wheel brakes are actually
good because, as we know, on cars and light trucks and other vehicles the front brakes
actually do most of the braking. They do 60 to 75, maybe even 80% of the braking
in really hard braking situations. And if you got the questions wrong, I too
initially got the question wrong, and I would like thank DC Fitness for pointing that out,
so that I could make amendments and bring you the best information possible. So front brakes are good under all conditions;
the answer is true, but if you’re driving a truck that has a manual front-wheel limiting
valve and it’s slippery out, you can put it into the slippery position. Most of the front-wheel limiting valves are
automatic and most of the time you’re not even going to know they are there. However, in a hard, hard, hard, super hard
brake application–more than 60psi–you’re going to have equal braking to the front steer
axles as you will to the back. So, front wheel brakes are good under all
conditions – true. Last question: how do you know if your vehicle
is equipped with anti-lock brakes. You know that it’s equipped with anti-lock
brakes because you turn the key to the on position – the orange ABS light on the dash
will come on momentarily and then go out. If it’s an older vehicle equipped with ABS
brakes, after you obtain five miles per hour the light will go out. If the trailer has ABS brakes, down the side
of the trailer there will be a light on the driver side near the rear of the trailer which
you can see in the driver’s mirror. If you’re not sure, go out to the brake chamber
– the airline running to the brake chambers will have an electrical line zippy tied to
it. That’s the other way that you can know that
you have ABS brakes. So in this video we’ve gone over section 1
of the CDL airbrake manual for the state of California. I’ll put a card up here for you for the second
video for section 5.2 of the airbrake manual. I’ll go over that. Section one essentially covered the parts
of an airbrake system: the air compressor, the governor, the air gauges, application
pressure gauge, spring brakes – most common types of foundation brakes: ‘S’ cam brakes;
CamLaster, wedge brakes, disc brakes and those types of components. As well we went over ABS brakes and whatnot. This is section 1 of the CDL manual for the
state of California. Section two is available and the rest of it
as well. And chapter 6, which goes over semi-trailers. If you like what you see here share, subscribe,
leave a comment down in the comment section. If you’re going for your CDL license and embarking
on a career as a truck or bus driver, check out the videos below. All of those will help you out in the bid
to get your license and be successful in a truck driving career. As well, check out the cards in the upper
right-hand corner. All those will give you great information
to be successful on your CDL license exam and as a career as a truck or bus driver. Question for my smart drivers: was there a
question on the CDL airbrake exam that tripped you up? Leave a comment down in the comment section
– all of that helps us out. I’m Rick with Smart Drive Test. Thanks very much for watching. Good luck on your road test. Remember, pick the best answer, not necessarily
the right answer. Have a great day. Bye now.

Leave a Reply

Your email address will not be published. Required fields are marked *