There are some occasions where you're going to need to bleed your brakes.
Maybe you've changed the hose and shortened it, sometimes your brakes start
to feel spongy, or just a bit of annual maintenance.
So this is how to bleed a Shimano brake.
You will need brake fluid, mineral oil for Shimano brakes, other brands use DOT 4 or
5.1 oil. Make sure you get the right stuff, otherwise you're going to mess up
your seals. A Shimano bleeding kit, which is a funnel and a syringe,
a brake block, a 7mm spanner, some Allen keys, some brake-cleaning fluid or
similar solvent, and a rag.
First thing I'm going to do before I even start bleeding the brake is give the hose
a quick check-over, just visually check there's no holes in it or anything like
that that's going to let in any air into the system, and check the connectors at
the brake lever and down at the caliper are nice and tight. Adjust this brake
lever to about 45 degrees on the handlebars. Then I'm going to make sure
this free stroke is wound all the way in clockwise, which mine is,
because I like there to be minimal movement on the brake lever.
So now I'm going to remove the pads from the caliper. First thing you need to do is
remove that clip from the pin, put that somewhere safe. Then I'm going to need a
little flat-blade screwdriver, just to remove the pin that holds the pads into
the caliper. Once you've got that pin out, the pads should just come out of the top
of the caliper like that.
Okay, so now you want to gently push these pistons back into the caliper.
Use something soft like a Tuff tire lever or something like that,
don't really want to use a metal screwdriver or anything like that,
as it can damage the pistons and the caliper.
If when you're trying to push these pistons back into the caliper,
you're pushing one in, but it's then pushing the other piston back out,
you're going to have to forget about this for one second and go up to the lever and
move on to the next step, and come back to that caliper.
So I'm up to the brake lever and I'm going to remove this bleed screw using a 2mml
Allen key, just when you remove that, be careful to make sure you get that tiny
little o-ring and place that somewhere safe. Now I'm going to attach the funnel
of the Shimano bleed kit, make sure you don't cross-thread this,
because they're quite delicate little plastic threads.
So now I'm going to go back down to the caliper, and those pistons should now push
it back into the caliper a little bit easier, because it's going to let some oil
out and into this funnel.
Now I've got the pistons pushed back into the caliper. I've fit this bleed block to
the caliper, and just secure it using the pin that you used
to keep your brake pads in.
Okay, so now we're ready to start bleeding. I know some people like to take
that caliper off the bike so that you can get it directly underneath the brake
lever, so if you are trying to do the rear one, you might want to tip the bike up,
just to get the caliper a little bit lower than the brake lever.
Okay, so half-fill the syringe with mineral oil. Once it's about half-full,
tip that up so you've got that bubble, comes right up to the hose,
and just try and push that air out of the syringe, and the hose
is completely full of oil, no bubbles.
Okay, so I'm going to remove that little rubber boot that's on your bleed nipple.
When I'm attaching this hose to the bleed nipple, I'm pushing on it ever so
slightly, so that I don't get any air bubbles in that hose
as it goes over and onto that nipple.
So using your 7mm spanner, just give that an eighth of a turn,
so that opens up.
So now I'm pushing gently on the syringe, pushing fluid through the hose,
and it'll come up through the system and into my funnel up at the brake lever.
When the oil goes black like that, the performance of your brake isn't brilliant,
so try and flush the new fluid through, maybe two or three times a year.
But the idea is just to flush fluid all the way through, so that it's pushing all
the bubbles out of the top and into this funnel. So keep pushing on the syringe
until no bubbles come through and into this funnel. If, like me,
this funnel's almost full, and my oil's still black, I'm just going to tighten up
the bleed nipple on the caliper with my 7mm.
Okay, so my bleed nipple's tight on the caliper. I'm just going to use this
plunger in the funnel, just to plug that up, so I can then remove the funnel from
my bike without dropping any oil, and I'm just going to dump this oil.
This is black, used oil, so it's no good to me. So get rid of that somewhere safe.
So I've reattached the funnel, pulled out the plunger, and I'm going to stick some
more fresh oil in the syringe and go again.
So I've pushed all that fluid up and through, you can see there's some fresh
fluid coming out of the brake lever and into the funnel now, some nice orange or
pinky color like it's coming out of the syringe, and also I keep pushing until
there's no more bubbles coming out of that brake lever. If they're still coming out
sporadically, you can start just tapping the hose a little bit with your little
spanner, just to free up any air bubbles and get them loose and get them traveling
up and into this funnel. And keep going until there's just fluid
coming out and no more air bubbles.
Okay, so just tighten that bleed nipple, and then we're finished with the syringe,
so take that off and just give that a quick wipe, just to get rid of any
overspill of oil, just for now.
Just give your brake lever a feel now, should be feeling nice and firm if you've
got rid of that air out of the system.
So a little pro tip here, just to make sure you've got all the air out of the
caliper, is to attach the hose, and if you use something to collect the oil,
I'm using a rubber glove so it looks good, and I'm going to use my 7mm again,
and I'm going to pull the brake on now, so I'm putting a bit of pressure into the
system, and I'm just going to undo this nipple an eighth of a turn,
and then quickly tighten it back up, so I'm just really quickly letting a little
bit of oil come out. So if there is any air in this caliper, it's just going to
pop out. Just make sure you tighten it back up nice and quick.
So as I've just undone the caliper bolt a couple of times, really quickly,
to let oil fire out of there, and any air bubbles, I'm just checking that the oil
level isn't dropping too low in this funnel. If you let it drop,
it's going to let air come into that system from above, so keep plenty of oil
in there. My lever is now feeling really nice and firm, so I'm pretty sure I've got
all the air out of the system.
Okay, so the bleed nipple's tight on the caliper now, I'm coming back up to the
lever, and I'm just going to undo the bolt and just move the lever around,
so bring it up level, or even a little bit higher than level, and we're just trying
now to pump the brake lever a few different angles, try and get any air
that's still stuck in this master cylinder out and up through the funnel.
So give it a little bit of a tap as well, and any air bubbles should then be
released. So with it flat, I'm pumping on the brake lever, nothing's coming out,
I'm going to drop it a little bit, again making sure that the hole at the bottom of
the funnel is always covered up with oil, so no air can drop into the system.
A few more times, and I reckon I'm good to go. So all the air is out of that system,
the brake's feeling nice and firm. I'm just going to do that back up on the
handlebars. And I can use the plunger again, just stick that into the funnel so
no oil drops out, and then remove the funnel from the brake lever.
So just before you put that bleed nipple back on, you might want to put a couple of
drops of fluid just in the top to top it back up.
Then screw that bleed nipple back in.
We have a rag to catch any oil, and then use a bit of this solvent again,
just to get rid of any oil on the caliper. I'll make really sure I'm doing that,
because you don't want any oil to get onto your brake pads when you've replaced them.
You can stick your little rubber cover onto that nipple,
stop any dirt getting on there.
So, pads back in. So, your Shimano have an R and an L for right and left,
so get them correct. Also make sure you're not getting your oily fingers all over the
braking surface, just slide those back into the caliper. Put your pin back in and
remember the clip on the end.
So front wheel's back in, and just give that lever a few pulls.
It might feel a little bit different, as it's just pushing the pistons back in
towards the brake disc, but now I've done that, it feels really nice and consistent
and I know that I've done a really good bleed of this brake. Quite often you don't
need to do a whole bleed like I've just done, you can just attach the funnel and
drop a bit of oil in there and just give that lever a bit of a pump.
Often the air rises up and into this front brake lever or your back brake lever,
but it rises up the system, so it sits just in the top here. So it's using that
funnel as a really quick, easy way of just giving the brake a flick-over,
and getting the air right and just dropping a little more oil in.
If that doesn't work, this full bleed, like I've just done,
should really just do the trick.
So once that's done, you might need to center your caliper again,
to get that disc spinning nicely in the center, and just reset your brake lever
how you had it before, the reach and the free stroke.
So there you go, there's how to bleed your disc brake. It's not the nicest of jobs,
it's a little bit messy, but it's actually quite easy to do, so have a go.
If you want to see more videos from GMBN, you can click up here for how to check
your disc brakes, or click down here for how to how to brake like a pro.
Or click on me and my fresh new oil to subscribe to GMBN.