- Now the reason for bleeding disc brakes is that
sometimes your hydraulic brake lines can actually become
contaminated with dirt, air, or in some cases even water.
Obviously that results in poor braking performance.
So today we're gonna look at how to bleed
the SRAM hydraulic road disc brake system.
So you can get stopping better again.
(jazz music)
So what you are gonna need is a bleed kit.
So in this case I've actually got a SRAM professional
bleed kit.
Inside of her I've got the DOT fluid oil, I've got
the syringes, hose attachments, all of the necessary
things as well to space out the calliper and make
sure we do the right job.
Also you're gonna need a workshop towel or a lint-free
cloth, some nitrile gloves, isopropanol alcohol,
and also a toe strap, or failing that an elastic band
that will come in very handy later on.
So today I'm gonna be bleeding the front disc brake.
So first of all I'm gonna remove the front wheel.
And then remove the little clip that's on the pin there.
And then with a two-and-a-half mil hex wrench, remove that
pin and then remove the pads.
And then, gonna put in there a little bleeding block.
Now that block that I'm gonna put in there is actually
really useful because it actually stops the pistons
from moving and potentially popping out if you touch
the lever.
So make sure you put that in there, keep safe.
So this is where you really do need those nitrile gloves.
First up, we're actually gonna screw
the bleed clamp assembly into the syringe.
And then, gonna fill it half full or as close to half full
as you can get with the DOT fluid.
So, keep a good eye on that.
And then, when it's about full, stop.
And now, gonna hold that syringe up this way.
With a shop towel just basically what we wanna do is
get rid of this air, so, gently force that up
using the towel to catch any residue and remove
those air bubbles.
So you are gonna have a little bit of fluid come out.
Maybe give the syringe a couple of taps
just to release any more air.
Give those clamps a good wipe down.
And then lock the hose in position
so it's like that.
So the next step is actually to remove as many pockets
of air that are in this DOT fluid as possible.
Now if you look at it, doesn't look like there's
any air in there, but there is.
Does get trapped in.
So how we gonna do it?
Well, make sure that that clamp is still locked down
and then gently pull the plunger.
And as you can see, look at that.
Look at all those bubbles that are rising.
And then gently let it back.
And repeat this process quite a few times.
We wanna get as many of those bubbles out as possible.
You may wanna hold it and just flick it a few times,
just to get rid of them.
Try and get rid of as many of those air bubbles as possible.
It's gonna help in the long run.
So just be very patient with it.
Just keep repeating.
Then, with the other syringe, you're gonna do exactly
the same but fill it just quarter full.
And then we move on to the next step.
(jazz music)
A quick check to do is actually to measure that the blade
of the lever is not more than 90 millimetres away from
an imaginary line using the brake lever hood as a guide.
If it is, then the bleeding procedure is just not
gonna work properly, and you're not
gonna get effective braking.
So if that lever's more than 90 mil, then just put a
two-and-a-half millimetre Allen key in there and just
turn it and just bring that lever inwards.
And then remeasure.
Make sure it's under 90 mil.
(jazz music)
So now with a corresponding brake lever, peel back the
lever hood and then undo that bleed port screw.
Keep it somewhere safe.
And if there's any excess oil at all, or DOT fluid,
just wipe that away, keep it nice and clean.
Then, gonna wanna thread the quarter full syringe into that
key port.
So next, we're gonna remove the little bleed port screw
of the calliper, and with the bleed kit we actually
get a little T10 key, so you're just gonna want
to remove that.
And then, just wipe away any excess
that may have popped out.
And now we do a half full syringe.
Simply screw that into the bleed port of the calliper.
It's important you get them the right way around,
so it's the half full one in there.
(jazz music)
So now we're gonna release those hose clamps
and then gently on the calliper syringe, push that in
so that the lever syringe goes to about half full.
Now, you will see a few air bubbles probably pop
up into there, don't worry about that.
But just make sure it doesn't go any more than half full
and then just lock down that clamp on the lever.
So using your toe strap or elastic band, just hold
the lever blade in up against the handlebar there,
make sure it's nice and snug and doesn't move.
So now you're gonna wanna hold the syringe vertically
like so, and then gently pull out, which as you can see
there's some air there coming out of the calliper,
that's exactly what we wanna be doing.
Removing all of that air.
And when the bubbles have finally stopped rising,
you gently push it back down in.
Just repeat that process a few times.
Just to make sure that we're getting all of the air out.
As you can see there's some more air coming out
of the calliper.
So now what we're gonna need to do is actually remove
the elastic band from where it's holding the lever in place.
But at the same time keep the lever in place with our hand.
And then, you're gonna wanna gently push the calliper
syringe inwards and at the same time just allow the lever
just give it a little bit of resistance with your hand,
just allow it to return to its normal position.
So once the lever's returned to its normal position,
simply clamp that hose and unscrew the clamp from
the calliper and then refit the bleed port screw.
It's to one and a half Newton metres, now that's not
a lot, and it's very fragile down there, so don't be
tempted to torque it up loads, otherwise gonna end
up stripping the thread.
Okay, so now we're going to release the clamp on the hose
and then simply pull and release a few times just
to remove any bubbles from the reservoir here in the lever.
Then you're gonna wanna squeeze the brake lever
into the handlebar and out about 10 times
and then repeat the process again, pushing and pulling
trying to remove any air from the cylinder up here.
Just repeat that process two or three times.
Just wanna get all of the air out of the system.
So now that you've got all of the bubbles out of the system
just apply a small amount of pressure.
Just back into the lever that way no air's gonna
get back into the system.
And then close off that clamp on the hose.
And then unscrew it.
And then refit the bleed port screw on the top of the lever.
Now with your isopropanol alcohol, simply put some onto
a cloth and then give, just clean
so make sure that there's none of that laying around.
Because it's not particularly good for any rubber
or handlebar type.
And then you can do the same thing as well, just down there
on the calliper, make sure there's
none of that hanging around.
(jazz music)
So now, just remove that bleed block and then refit the pads
and your wheel, and give the brakes just a couple of
little tugs and make sure that there's no leaks at all
from any of the seals.
There won't be though, if you've
followed my instructions carefully.
Right, well I hope that your disc brakes
are now working perfectly.
Let me know in the comments down below how you got on.
Keen to read them as ever.
Also remember to like and share this video with your friends
and if your disc brakes don't need bleeding
but just a little bit of TLC,
click just down here to find out how.