Henry’s Disc Brake Hacks | Mountain Bike Brake Set Up Tips

Henry’s Disc Brake Hacks | Mountain Bike Brake Set Up Tips


– Bad feeling brakes can completely throw out a whole bike for me, it’s really, really important to get a nice positive feel, and although it’s a very subjective thing, how you might want them, there’s no reason you
can’t maximize your brakes. So what we’re going to look at is ways to fine-tune them without reaching for the bleed kit. This is stuff like set up, and all that sort of shabaz. So we’re going to get into it, look at some really kind
of fine-tuning details and go from there. Before we even get to our bike, we’re going to ask ourselves
some existential questions. Why are we here? Why would you buy jeans with
holes already cut into them? And where does the oil go in my brakes? Now sometimes, people
complain about you know, spongy or gradual feeling in their brakes, and they immediately
think it’s a bleed issue. But I want to explain why
that’s not always the case. Now, back in the day, they used to use what
we call a closed brake. This means that the whole
system was entirely sealed, and as the volume of the
oil increased under heat, the lever flow, the amount of
lever travel would be reduced. So think of, you know, your
Hope C2’s or your Giant MPH’s, and people would actually run their brakes further in than they’d like, in anticipation for that oil expanding and that would reduce
travel further down the run. I don’t think we really, really appreciate how good and consistent modern brakes are, because what they use is
what we call an open system. So on every single kind
of modern brake lever you will find a small hole. Now that hole basically leads
to kind of a small pocket, a small air chamber and
there’s a diaphragm in there. Now the diaphragm keeps the
oil in the air chamber separate and as the oil temperature heats up and the volume expands, it
pushes on the diaphragm, which in turn pushes on the air chamber. Now that little hole is to self regulate and air will kind of be coming
and going as you please. Now let’s look at the systems used within a Shimano brake for instance. Now Shimano uses, essentially, one pressure system inside the brake, which is gravity bled. That means that oil works
it’s way towards the bottom and air works it’s way towards the top. That’s why a bucket system is so effective on a Shimano brake. TRP is another example you
could use a similar system. Now this is robust, it’s simple, but it does sometimes have issue in terms of when the pads wear faster than the system can adapt. Which I’m going to get to in time as well. Other brands including say SRAM, or Avid as they were known, use two pressure systems
within their brakes. So at the lever, you have
the high pressure system and in the hose and the caliper you have the low pressure system. You might have seen that
when bleeding the brakes, first, you cycle the oil through, bleeding the low pressure system before moving on to the lever which is the high pressure system. Now the low pressure system controls the power at the caliper and the high pressure system
largely controls feel, but what happens is like
any two pressure systems the eventually try to equalize over time. So today we’re going to, a bit later on, we’re going to look at
readdressing the balance. So now we’re going to talk about what we’re going to use
within this service. So first on the list is the
oil that your system uses. SRAM used Dot 5.1 and
if I used mineral oil which you’d find in a
TRP or Shimano system it would actually corrode
the seals and vice versa. So please use the oil
specific to your system, that’s number one. Number two, mister cable
tie, I have a plan for this, don’t worry, you’ll understand in a bit. Number three is another weird one, cotton buds, these just so
good for cleaning small areas and I’ve got big sausage fingers there’s no way I’d be
able to clean pistons without these bad boys. Then we’ve got a 4 mil, a number 5 mil, T25, a Park pad tool spacer, which is the unsung
hero of many workshops, a very small and very clean
flat head screwdriver, a thimble full of brake cleaner and a plastic tyre lever. Last but not least, we have yet again some very
clean Fresh Prep blue towel. Obviously you can use any
old rag or kitchen towel, whatever, but as long as it’s clean and of course some rubber gloves. Please wear gloves. I have got the horrible leathery hands of a Gibraltar pensioner
and I still wear gloves. If you’ve ever got some
corrosive fluid on your hands and your skin has came
away, like wet tissue paper, you’ll understand the importance. But the gloves aren’t just protecting us, they’re also protecting the bike from contamination from you. If you don’t use gloves
make you really wash your hands properly before you start. All that, kind of natural
oil that your hands secrete, can contaminate motors, it
can contaminate brake pads, and if we’re going
through all this effort, to making sure our braking
system is as good as possible, why compromise it with something to basic. When we’re handling brakes, want to be really careful not
to touch the face of the pad, not to touch the brake
and tract on the rotor. I want us to really think
about and concentrate on, putting all these small changes in, to really maximize our braking. So as you can see I’m taking
the wheel out of the bike, putting that disk far, far
away from any risk of oil. And I’m going to do that
same with the pads as well. Such a stupid way to contaminate anything, so let’s be sensible, let’s
get our thinking caps on. So that, Mr. Wheel, you
can live down there. Weirdly enough as well, normally
I’d put the axle back in, which is only a small detail I suppose. But we’re going to be doing a
lot of work on this caliper, and we’re going to need that out the way. So I’m just going to put
that on the side there. So the first thing
we’re going to get into, is basically making sure, our pistons are running with as little, having to overcome as
little friction as possible. Some of the times, there
can be so much friction, within the seals on the pistons, that the reason your brake
feels like it spongy, is because right from that
first bit of that lever throw, it’s actually having to
overcome a lot of friction. So it’s not free falling, until it hits, you know,
the bite, the bite point. So, we want our piston to
be running really smooth. So what we’re going to do is,
we’re going to lube up our pistons, with the correct oil. So if you’re using Shimano that’s mineral, SRAM, AVID, that’s Dot, and always, you know, two second google can
save you a lot of bother, so depending which brand you have, if it’s one of the, perhaps
one of the other one, just give it a quick check
to make sure it’s all good. So, let’s get into it. With our calipers, you will see a small slot
where the rotor goes in, now an AVID takes a 4 mil
allen key there, really neatly. On a Shimano I think it’s
a 3 mil, it normally is. We want to get kind of, you know, the largest allen key in
there that you can fit. Without cramming something in there. So we’re actually going to
use this, as a control point. Just to get the pistons sat
out so we can clean them. So I’ve got a 4 mil tucked
in the slot there neatly, and I’m just going to pump the brake. As you can see, the pistons
are coming straight out. Sometimes, one by one,
sometimes all together. The more active a piston is,
the quicker it comes out. But what we want is a really
well balanced caliper, where, in an ideal world, all
the pistons would come out, the exact same amount,
at the exact same time. That doesn’t always happen in reality, but can can normally get it pretty close. So now this is where the fun
begins so my gloves are on. What I’ve got here is a small
thimble full of brake cleaner, which is all you really need for this, and I’ve got a cotton bud, what we’re going to do, is you’re going to work round
each cotton bud individually. You can see, I mean these are actually relatively new brakes. You can see how much dirt
and grime comes off there. I think because they get
so hot under braking. And all that dirt when
you press the pistons, back into the caliper, will be working their
way towards the seal. But we’re just going
to do this outer edge, nice and clean, Spic and Span. And then, I’ve got my Dot fluid, and what we’re going to do,
we’re going to get our cable tie, and use it as almost and
applicator for Dot fluid. Now we’re not tryna douse them, we’re not pouring it
over the whole caliper. We’re applying small amounts
of it to the pistons, okay? So you just start at the
top and just wipe round. You almost want it to be, just one ring going around the piston. Then what we’re going to do is, we’re going to get a plastic tyre lever. Now, you’d often see people
use metal tyre levers or, you know, these pad spacers, on pistons. I’m something I’m loathed to do, just because, these can sometimes
be kind of brittle metal, and they can just shatter, I’d rather not run the risk, and use a plastic tyre lever personally. We’re going to go back to the 4 mil. We’re going to put the 4 mil
between two of the pistons, and we’re going to push the other two back with the plastic lever. If we don’t do this, and we
don’t have that 4 mil in there, as we push one back, that piston, one of those pistons could
just pop out the caliper, and then you’ve got to bleed the brakes, and everything and it’s quite a palava, so we don’t really want to do that. So with that 4 mil in there, we’re just going to work
at these two pistons, and just tease them back in. Until they’re sitting, nice and flush. Remember that face of the piston, should be parallel with the caliper, should be going in squarely okay. Now we’ve got those two in flush, we can just work on, bit by bit. Just moving these ones back, annoyingly enough for everyone, we’re actually going to put that 4 mil and we’re going to bring
those pistons back. What we’re actually going to
try to do is lube the seals, and not leave any residual oil just left hanging around the pistons, cause that’s only going
to increase the likelihood of contamination. We’re just going to bring
them out and clean them again. Now that the brake is out we just go back, we just go back with our
thimble and cotton bud and basically just make sure
everything is Spic and Span. Look at that. So here we go for our 4 mil again. Tyre level again, we just push
them back in one more time. So now everything is completely
flush within the caliper. Now that’s really important. For the third and final time. We get our cotton bud, we get our thimble, and we’re just going to
make sure it’s all tidy. There we go, beautiful. Sweet, so I’m pretty confident
that that is nice and clean. Because our gloves could have oil on them, what I’m going to do, is I’m
actually going to take them off, cause you know, there was quite
a lot of oil going on there. And I’m going to be incredibly careful, I’m not going to get a set of
new gloves, though you could do, I’m just going to be really careful, and we’re going to
touch the backing plate, and the side of the pads. I’m not, not, to repeat, not,
going to touch in there, okay. And then we’re just
going to drop them down. Make sure they’re seated all good. Perfect, we’re going to
get the all important, the all important retaining bolt. Nobody is a good enough mechanic, to not have to worry
about this little fella. I know somebody who I consider
to be a very good mechanic, and he forgot to put one
of these in a World Cup, World Cup finals one. Ohh, no no no no. Oh deary me. Now, what tends to happen, is oil from the high pressure
system migrates to the low, this is just wear and tear, this is used, this is the two systems being exposed to each other. Once we rebalance, these
systems you’d be amazed at how much positive feel
comes back into your brakes. Now what this involves, is I’m
going to pull on the brake, until I get a nice bite, and I’m going to push both pads back, whilst gently flicking the lever. What this does is it actually opens up a port on the lever end, and it let’s that oil get back into that high pressure system. At this point we’re going
to reintroduce the wheel. And we’re going to look at the alignment, and I’ll tell you how that can affect the brake performance too. Now you might of noticed on
some calipers or adapters, they actually come with
these kind of, comb washes. Now what this is to do,
is to make sure that, this braking service here,
is perfectly perpendicular, to the braking surface. So I want you to imagine
that if these were an angle, it would twist the whole
caliper on it’s side. And these kind of you
know can account for that, that lack of tolerance is suppose. Also when you’re having
a really big adapter, or a really big rotor, and the braking service is
farther away from the axle, the more that it exaggerates this problem. So I’m actually, yeah, taking no notes of what
the pads are doing, and I’m getting that rotor
centered exactly in the caliper. It spins freely because the
pads aren’t there at all, but it’s yeah, well and truly square. Now what were going to do, is we’re going to reach
for our very small, very clean flat head. And we’re going to gently, and gently being a very important word, pull on this lever here. As we pull it, we’ll
start to get a good idea of what the pads, what
the pistons about to do, and this front right piston
is slightly over active, so I’m going to, let go, that’s all done for a moment. And using the edge of
this Phillip screwdriver, I’m going to go behind the
pad, just opposite to it, and push that caliper
back so it’s flush again. This will mean the other pistons, then have kind of a bit of a head start. Sensational. Let’s have a feel at that bite. Oh that feels incredibly positive. Like I said, it’s still
though worth doing, just a few, a few times cycling
that brake whilst riding, just to wear that pad, exactly parallel. You can also, if you have
really cooked your brakes, is the tried and tested tip. Don’t be afraid just to
get some sandpaper there, scrub up the rotor, not in
the direction of travel. Same again with your pads, if your pads are over like,
shiny, or anything like that. Just take the edge off, and that’s going to really increase bite and braking performance. It’s a bit like, you know, you can have the best suspension, and the best geometry in the world, but if your tyres aren’t gripping because the pressures wrong, and you’ve got you know, 60 psi, it doesn’t matter, it doesn’t
matter how good your bike is. Similar to your brakes, if your pads and your rotor
are absolutely cooked, you can have the best bleed, the fancy pants four
parts with ultimate power, it’s not going to make any difference. That’s the contact point,
that’s the most important point, so contamination, I’m going to go on, it’s probably going to become a theme, you’re all going to hate me, I don’t care, contamination’s important. And those are some of my top tips for how to optimize you’re
braking performance. If you’re wondering, who the hell I am and what I’m doing in
the GMBN Tech studio, please click here to see my introduction on the GMBN Tech show. And if you came here by happy accident, or this isn’t, you’re not
really interested in it, but you did want to find out
how to bleed your SRAM brakes, click down there. Thanks, like and subscribe, brrah!