[TITLE: HOW TO DETERMINE AIR BRAKE ADJUSTMENT :: APPLIED STROKE | PRY BAR | MARK & MEASURE]
Hi there smart drivers, Rick with Smart Drive Test
talking to you today about how to
determine that the air brakes are in
adjustment. This is particularly relevant
for people getting a CDL license, class 1
or a class 3, D in
Ontario... Any bus or other vehicle that's
equipped with air brakes; if you're going
for a license, you're going to have to
demonstrate how to determine if the air
brakes are in fact in adjustment,
regardless of the fact that for almost
20 years now we've had automatic slack
adjusters on these vehicles. You still
need to determine that, in fact, the air
brakes are in adjustment. There's two
methods of doing that and in California ,New
York, British Columbia and most of the
provinces in Canada, they all use the pry bar
method, sometimes called the free stroke.
But most often referred to the pry bar,
because you use a pry bar to determine
adjustment of the air brake system. The
next one is the applied stroke - in
Ontario, Canada I know that they use the applied
stroke method. And if you get pulled into
the scale or pulled over by the DOT (Department of Transportation),
the CVSE (Commercail Vehicle Safety & Enforcement), the MTO (Ministry of Transportation in Ontario) in Ontario - any one of
of those diesel bears - they are going to do
the applied stroke method. And the way
that they do that is, they put a radio on
the door of your vehicle, they go
underneath the vehicle and they put a mark
at a fixed point on the push rod. And
then they get you to apply the brakes.
They then measure from that fixed
point out to the mark that they made on
the pushrod. So today we're going to go
over and we're going to show you how to do
both the pry bar method and the applied
stroke method so that if you get pulled
over by the diesel bears, you don't get a
fine and you don't end up working the day
for free. And if you're taking a license,
you're going to be successful on your
license. Stick around, we'll be right back
with that information.
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Hi there smart drivers, welcome back. Rick
with Smart Drive Test talking to you
today about how to determine if your air
brake system is within adjustment. If
you're going for a license or you get
pulled over by the diesel bear--the DOT,
the MTO, the CVSE, or any one of those
authorities, they're going to check the
brakes on your vehicle and ensure that
they are within adjustment. And to
determine if they're with an adjustment
they're going to use the applied stroke method.
There's two methods that you can use to
determine that your air brakes are in fact
an adjustment on an air brake equipped
vehicle: 1) one is the pry bar; 2) and the other is
the applied stroke method.
Safety first on both of these methods,
regardless of which one you're using, the first
steps of that are two chock the wheels on
your vehicle. Then release the parking brakes
and ensure that the pressure in the
system is above 90 pounds. Because you
need more than 90 pounds in the system
to have those powerful spring brakes
that apply the parking brakes completely
released. So you need more than 90 pounds (psi - pounds per square inch)
in the system - so safety first!
Chock the wheels, as you can see here in
the image. Get in the cab, release the
parking brakes and put your foot over the
service brake just in case the chocks
don't hold and the vehicle begins to
roll away on you then you're ready in
the event that that does occur by
applying the service brakes and then
ensuring that you have more than 90 psi in
the system. So that's the first step.
For the pry bar method you simply need a pry bar,
thus it's called the pry bar method. You
put the pry bar in at the clevis pin and
pry out. And the pushrod should not come
out of the brake chamber more than half
to three-quarters of an inch. In the
state of California and New York, they
both allow you an inch, which is fairly
lenient in terms of how much travel is
allowed on that push rod, but essentially
half to three-quarters of an inch.
You don't need a measuring device,
essentially the width of your thumbnail
is all that push rod should come out of
the brake chamber. So that's a fairly
simple one and most provinces in Canada,
most of the U.S. states all allow you to
use the pry bar method. The other method
is the applied stroke method. And again, the
same principles apply: 1) chock the wheels;
2) release the parking brakes; 3) make sure you
got over 90 psi in the system. Now for
the applied stroke method
you're going to need another person or
you're going to need a board or
something that will allow you to apply the
service brakes in the applied
position. So after you pump up over 90
psi and whatnot, you go around make
sure that you mark all the push rods at
a fixed point. Some of these will have
plastic tabs on them as you'll see when we go out to
the truck here. You'll see that this unit
that we're working on today has plastic
tabs on it that rest against the face
of the brake chamber. Most of the time
the face of the brake chamber is going
to be your fixed point for determining
if your brakes are in adjustment. So you
go around, mark all of the pushrods, if
they're not already marked or there aren't
plastic tabs on them as are there are on
this unit. You go back into the truck and
apply the service brakes in the fixed
position, so they're held on. And then you
go around the unit and you measure every
one of the push rods for how much travel there is when it comes out of the
brake chamber. Now on a type 30, which is the
most common on the back of trucks and
buses and semi-trailers, is going to
allow two inches of travel - maximum 2
inches of travel. So if you're already at
the 2-inch limit, you're going to need to
get them in adjustment and the way that
you get them an adjustment is with a
six-pack. And I'll explain that a little
bit later. So you're allowed a maximum of
two inches on automatic slack adjusters.
If you have, in the rare case, a manual
slack adjuster which you probably won't
have in this day and age, you're allowed
an inch and three-quarter. So maximum 2
inches of travel on a type 30. Now the
front steer axles, the brake chambers are going to have
different-sized chambers. If you're on a bus
or a smaller vehicle that has air brakes
on it you're going to have a different
size brake chambers Now what
determines your pushrod travel--how far
that push rod can extend out of the
brake chamber--is the size of the brake
chamber - so the diameter. So essentially,
if you get pulled over by the DOT, the
CVSE or some other diesel bear, what
they're going to do is going to take their
calipers and are going to measure the
diameter of your brake chamber. And then
they're going to look up on their chart
and they're going to determine what size
the brake chamber is. And from what size it is will
determine how far the pushrod can extend
out of the brake chamber. So if you're
going to a driving school and they're
sending you to for license, they're going
to tell you how far that can extend out
of the brake chamber if it's an applied
stroke method. In most cases, it's not
going to be an applied stroke method.
So you measure all of them, determine
that there within adjustment. If they're in
adjustment you're good to go; if they're
not in adjustment and their automatic
slack adjusters you want to do what's
called a six-pack to walk them back into
adjustment. Because there's a couple of
reasons that automatic slack adjusters
will go out of adjustment: first of all,
they don't get enough grease; or second, there aren't hard enough
brake applications to ratchet it over to
the next notch inside of the mechanism.
Because essentially, that's all it is is a
ratchet mechanism inside of the
automatic slack adjuster. So what you do is,
keep your wheels chocked, go back and make
sure your parking brakes are released. Pump
the system up to maximum pressure and make
three hard brake applications. By the time
you make three hard brake applications, you
are going to be below 90 psi, so
pump the system back up to maximum pressure again.
And again, make three more full hard brake
applications. That's called a six-pack!
Once you do that, often times, you go back
up to the automatic slack adjusters and
you check them again -
oftentimes those six hard brake
applications are enough to walk your
automatic slack adjusters back into
adjustment. So you just check again - if
they're not an adjustment after you do a
six-pack you basically take the unit to
a mechanic and they'll swap out the
automatic slack adjuster, because at this
point that's what's wrong. It just simply
needs to be replaced. Sometimes you can
put grease to them, because if they dry
out oftentimes the ratchet mechanism
won't work. So you can put grease to them
and try another six-pack and sometimes
that might walk the automatic slack adjuster back into adjustment. For
the most part, the slack adjuster simply needs to be
replaced and you're going to have to go
and find a mechanic to do that
for you.
So today we're going to go to the truck
here we're gonna show you both the pry
bar method--sometimes called the free
stroke method--and the applied stroke
method on the truck. Now we're going to
get underneath the semi-trailer because it's
easier to video that for you and give
you a better image of how that is done.
It's actually--once you see it, it's
actually--quite simple to determine
adjustment of air brake systems and
determine the brakes are in fact in
adjustment. So let's head out to the
truck.
Hi there smart drivers, welcome back.
Rick with Smart Drive Test talking to
you today about checking pushrod travel
adjustment for air brakes and
determining that your air brakes are in
fact in adjustment. So the first test
that we're going to do is the pry bar
method or the free stroke method as it's
sometimes called. This one is actually
quite simple and all you need for this
test in terms of tools--they do state
in the California State airbrake manual,
the CDL manual--that you can do this with
your hand, but you can't do this with
your hand. You can't pull that push rod
out of this brake chamber with just your
hand. So what I suggest, gloves. Always get
gloves to protect your hands - safety. You
need a prybar - catspaw works well. You can
have all kinds of different pry
bars. They have them at truck stops and
those types of places. You can pick them up.
They work really well, and in some
jurisdictions you might need a tape
measure. But as I tell students, it's just
the width of your thumbnail - half to
three-quarters of an inch in the
province of British Columbia, Canada. I know in
the state of New York and California, and in
other jurisdictions they allow an inch.
But for the purposes of what we're gonna
do today, we're going to use the width of our
thumbnail. And like I said, you can get a
tape measure and when you pry it out
just measure with this. But it is
approximately the width up your
thumbnail. So you can see here - just put
the pry bar on the clevis pin at the end
of the push rod and pry out on it. And
you should be able to determine that it
is within adjustment - half to
three-quarters. This is not the most
reliable test, but for the most part it
works well. And most jurisdictions allow
the pry bar test (free stroke method). Next test we're going to show you
is the applied stroke method and this
one is a little bit more involved. And in
the province of Ontario, Canada for
those students doing their test in Ontario, Canada
you'll have to have the tools to be able
to do this test. The applied stroke method:
1) wheel chocks, as you can see here in the
image, so you can secure the vehicle and
release the spring brakes on the unit.
And then you're going to have to do an
applied stroke method. As well with the
applied stroke method, if you get pulled
over by the diesel bears: the CVSE, the
MTO or the DOT in the United States,
the applied stroke method is the method
that they're going to use. Now as I said,
it's two inches of pushrod travel on a
Type 30 brake chamber. On different brake
chambers, for
example, on the front theses are smaller
brake chambers. It is the size--the
diameter of the brake chamber--that
determines pushrod travel. So what the
diesel bear is going to do is he or she is
going to measure the diameter of the
brake chamber and they're going to
look on his/her chart. And you can find--
i'll put a link down in the description
box there for the diameters
of the brake chambers to determine
maximum pushrod travel allowed.
And so if you're doing the applied struck
method on the front,
you're gonna have to determine that if
you go to a driving school. they're
already going to know what size of brake
chambers you have on the front of your
vehicle and how how much pushrod
travel you're allowed, but for the most part authorities are
going to do applied stroke method. On a
Type 30 brake chamber and with an
automatic slack adjuster you're allowed
two inches of pushrod travel. If you've
got manuals, which is very unlikely in
this day and age, you're allowed one and
three-quarter inch of pushrod travel on
and applied stroke method. So let's get
to the applied stroke method and show
you how to do that. So the applied stroke
method - when you get in the cab
you'll need to chock the wheels as you can
see here in the image and you need more than 90
pounds per square inch of air pressure
in the air tanks after you release the
parking brakes. If you don't have over 90
psi, the spring brakes are not off
completely. And you can't check the pushrod
travel on the applied stroke method. So
the other thing you're going to need to
do after you release the parking brakes
and have over 90 psi - you're gonna
need another person to hold the service
brakes on or you're going to need
something to hold them on, like a stick
that you can jam in between the brake
pedal and the seat. And for those of you
going for a road test and doing the
applied stroke method, you're going to
need a stick or some other method to apply
the service brakes while you're out
underneath the vehicle measuring the
pushrod travel after you've applied the
service brakes. And that's how you're
going to have to do that. So you can see
here on the push rod that there's a
marker--a yellow plastic marker--on the push
rod here. And this is going to be our
fixed point. If you
don't have yellow markers you can also
mark that with soapstone or you can use
a zippy tie. And you can put a zippy
tie on there, as well, for your fixed
position. Now what we're
going to do is we're going to in the cab
and we're going to apply the service brakes.
Alright, so we've got the service brakes
applied. We know that the face of the
brake chamber is our fixed point and
we're going to measure out to the yellow
tab on here. Because we know before we
apply the service brakes--released the
parking brakes and applied the service
brakes--that the yellow tab was sitting
right flush up against the face of the
brake chamber. So what we're going to do
is we're going to measure that distance.
And you can see that it's just less than
2 inches on that one
and on this one we can see that that one
is just under 2 inches as well. So both
of the trailer brakes are in adjustment.
Now these are close to the adjustment limit of two inches, so
basically what we would do is do a
six-pack on this, which is essentially go
in the cab, pump up to full pressure and make
three hard full service brake applications. Build the
pressure back up. And again release the
parking brakes and make three
full-service brake applications. Often
times, that will walk the ratchet
mechanism inside of the automatic slack adjuster back into adjustment - cause it to
ratchet over to the next spot on the
ratchet and bring them back into
adjustment. So that's something you might
want to do because these are very close
to the adjustment limit. But they are
within limits and you wouldn't be put
out of service if you got pulled into a
scale by the CVSE, the DOT, or the MTO in Ontario.
Quick review on checking adjustment
for air brakes. You have either the pry
bar method--the free stroke method--or you
have the applied stroke method. For the
applied stroke method you're going to
need something to hold on the service
brakes - a stick or another person.
Oftentimes, it's better if you have
another person to hold on the brakes for
you, but that's unreliable. So find
something that you can use to hold the service brakes applied. If you're
at a school and you're going to go for
driving test and you need to hold the
brakes on for the purpose of your road
test, obviously the school is going to have to have
something you can jam in there. So a
stick, and you're going to need a
measuring device. You're going to need
some way to mark the pushrod - a lot of
these trucks will just have the plastic
tabs on them as this one does,
as you saw there. And then what you do is
release the parking brakes, make sure
that you got over 90 pounds of pressure
to make sure that the spring brakes are
completely off. Apply the service brakes,
go back and measure from your fixed
point, which in this case was the face of
the brake chamber, and in most cases it's
going to be the face of the brake
chamber out to that plastic tab. And on a
Type 30 brake chamber with automatic
slack adjusters, you are going to need less
than 2 inches of travel. If you have a manual slack
adjuster, which in this day and age is
going to be unlikely, you're allowed an inch and three quarters. That's the
applied stroke method. And the
other one is the pry bar method or the
free stroke method. And you're going to
need gloves--use gloves for both of these
because always protect your hands and
keep the dirt outside of the vehicle. And
you're going to need a pry bar. And just
put this in the clevis pin at the end of
the pushrod - half to three-quarters of an
inch. In the state of California or New
York, you're allowed an inch. Most of the time you can just
check the the push rod travel against the width of your thumbnail. The pushrod
should not extend more than the thumb width
out of the brake chamber.
Essentially what you're doing is checking the freeplay -
the clearance between the brake shoes
and the drum. When you pull out on that
you're allowed half to three-quarters or an
inch in the state of California for that.
And in the state of California, they say
you can pry the pushrod out with your hand, but you
cannot do it with your hand, and you're
going to need a pry bar to pull that
push rod out of the brake chamber. So
that's how you do brake adjustment.
Question for my smart drivers: do you
check the adjustment on your brakes
every day or do you do it just when you
have hill checks and you're driving
through mountain? Leave a comment
down in the comment section there, all
that helps us out.
I'm Rick with Smart Drive Test, thanks
very much for watching. If you like what
you see here share, subscribe, leave a
comment
in the comment section. As well, hit that
thumbs up button. Check out all the
videos here on the channel - lots of great
information for those of you getting a
license or working towards a career as a
bus or truck driver.
Good luck in your license. And remember,
pick the best answer not necessarily the
right answer.
Have a great day. Bye now!
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