5 Common Mountain Bike Maintenance Questions

5 Common Mountain Bike Maintenance Questions


– In the weekly Ask GMBN Tech Show we quite often get asked a
lot of similar questions. So in this particular video, we’re gonna look at five of those real common maintenance issues and how you should tackle them. (pounding) (sword slash) Okay, so let’s jump into these questions. And the most common one
that seems to come up on a weekly basis here at GMBN Tech is, why do my breaks squeal? There’s a couple of
different ways they can work, but the fundamental results are the same, and if you’re getting
squeaking or squealing breaks it’s usually one of a few things. Now the most common one is that they’re not bedded-in properly. Now this happens more
often than you might think. So, the telltale sign
of that is by looking at the disc rotor surface itself, and what I’m looking for here
is an equal sheen across it. Note that I’m not actually gonna touch the breaking surface itself because oil in my skin
can transmit to that, which causes contamination, which is another factor that
can make your breaks squeal. But getting your breaks
bedded-in is the single most important thing in the first place. And the way you wanna be doing this, with a fresh disc rotor and
a fresh set of disc pads, is ride 15 miles an hour,
something like that, and you wanna do several
sort of firm stops. And the idea is you’re
depositing some of the material from the disc brake pad
onto the rotor surface. But you wanna be doing
it in a fairly even way so it applies it all the way round. After a while this takes and you’ll find that they
mate together really well and you won’t actually
get a squeaking brake. However, there are
still a number of things that can make them squeal and the next one on the
list is contamination. Now, contamination as I mentioned, happens usually when you’re getting oil, whether that from the brakes themselves, or something else on your bike, or even like I mentioned a minute ago, the oil from your fingertips. So if your oil or any type of oil gets near your disc brake surfaces, whether it’s the rotor
themselves or the brake pad, then actually you’re gonna find that these are gonna squeak and then the end result is they just simply will not work adequately and you’ve gotta do one of a few things. The first option is a spendy one, and that means buy some
new disc brake pads and new disc rotors. However there is another way around that, and that is gettin’ a complete
rejuvenation of your brakes. And the way to do that is take those brake pads off the bike, then you wanna clean these in somethin’ like isopropyl alcohol, that dries up and leaves no residue. Then you wanna scrub them down with a coarse emery paper or glass paper, then clean them again, scrub them again. You wanna make sure until there’s no sign of any contaminant in them. You can use dedicated
brake cleaners to do this because they evaporate as well, but avoid using anything
that could have any trace of any lubricant or oil
in it for obvious reasons. The same goes for the disc rotor surface. And once you’ve done this, you wanna wait for them
to be completely dry, then start the bedding-in
process all over again. If you’re lucky and your brake pads haven’t been too badly
contaminated, you can rescue that. And another cause of
brake squeal is vibration, which transmits into these
very fine oscillations, which basically make your
brakes vibrate and squeal. Now this can happen if your brakes haven’t been bedded-in properly and you end up with an uneven amount of material deposited on that brake rotor. You can actually see
this when it’s happened, it’s like the visual equivalent of braking bumps on your disc rotor. What happens is those disc
brake pads vibrate super-finely. If you think how fast the
rotor passes the pads, it’s like incredibly fast operation. And that will end up in some
kind of squeak or squeal, which can be infuriating. Now of course, vibrations can
also happen in other ways. It can happen if your
caliper bolts are loose, if the disc rotor bolts are loose, and course that’s incredibly dangerous so you wanna make sure
that all of your bolts are adequately tight all of the time. Another thing that can happen is, the actual disc pads themselves can vibrate slightly within the caliper. Now make sure that you’ve
got your retaining clip and the actual bolt that runs
through the back of the pads is on and is holding
your brake pads in place. Also in some cases, it has been known for particular bike designs to have that resonation through the frame that you just can’t get
rid of a squeaking brake. Tends to happen on the back
rather than on the front. As we have seen on a few different bikes, particularly on a downhill workup scene, is braking dampers that
basically absorb that resonation. Now on Gee Atherton’s bike, as you can see here on-screen, he actually has a
custom-made braking damper on his rear brake caliper. ‘Course this is a pretty unlikely
situation for most people. Think of someone like
Gee doin’ average speeds on a World Cup course when
he’s hangin’ on those brakes. It’s a bit different to you or
I doin’ regular trail riding. Now there is one other circumstance when your brakes can squeal. Now there are different
types of brake pad and, depending on what you use
them for and how you use them, it is possible to glaze the pads over. For example, you got
sintered and you got resin. The sintered pads have
particles of metal in them, they’re generally better
in wetter conditions, they cope with that a lot more, but they’ll also cope with high heat. Resin pads, less so. On a resin pad, when
it heats up massively, they can glaze over. So whilst the resin pad is
extremely good and powerful, they can suffer at the hands
of becoming glazed over. And when that happens, it feels like you’re running with
polished brake surfaces. So although the brake will work, you’re not actually
gettin’ that grabby feel, and as a result of that,
they can get a resonation, which again transmits into squealing. If that’s the case then you can start by renovating those brake pads just like we showed a minute ago, and the same with your disc rotors. But if not, then it might be time for new brake pads for you. Okay, so the next one on the list is also braking related and it says, why does my brake lever
pull close to the bar? Okay, so there’s a few
things that this can be here. So on any set of mountain
bike disc brake levers, you’ll find there’s gonna
be at least one adjustment. That will usually be the reach adjustment. Now occasionally that
can be wound in too far, which means your brake lever actually pulls really close to the handlebar as opposed to coming on straight away. So you can play with those. But the real reason your brakes end up pulling closer to the lever
is, actual brake pads wear. To compensate for that, the
pistons push out slightly and basically, the fluid
has to compensate for that. So you can counter that with
that reach adjustment dial, but it only goes so far. So you will find that at some point, you’ll max that out and your lever will start pulling closer to the bar. This also happens if you have
got some air in the system. So with air in the system, the case is, you’re gonna have to just
give your brakes a bleed because that is the way. You might just be able
to do a level bleed, which might be the answer for you, and that’s obviously a very quick and easy way around the problem. But as for the lever
just pulling to the bar because the pads have worn. Firstly, if your pads have
still got enough life in them and you’re happy to keep using those, then you can do what’s
called a mini-bleed, which is basically just
bleeding the lever. So the idea of overfilling
the brake lever is, you filling up the reservoir here with as much fluid as you possibly can, put the cap back on, and when you go to pull the brake lever, you’ll find, just because
you’ve overfilled the system, that the brakes actually
feel a lot more solid and therefore your brake lever will not be pulling all the way to handlebar. It’s quite a simple process to do. You can do this on SRAM brakes, you can do it on Shimano brakes, and Maguras and (mumbles),
most other brakes. And as you can see on-screen, I’m demonstratin’ here with
a set of Shimano brakes, but the principal is
very similar using SRAM. Except with SRAM brakes,
you tend to have to use a syringe in order to get
the fluid into the lever. You can of course, make sure
your levers are horizontal and add brake fluid directly to those. And of course with SRAM you need to make sure
it’s DOT brake fluid. With Shimanos and
Maguras and other brakes, it tends to be mineral fluids. So it’s essential that you get the right fluid when you do that. Okay, next up on that list is, why is it hard to inflate my
tires through a Presta valve? Okay, so to understand
what could be cloggin’ it, we need to identify the type of valve and make sure you’re usin’ the correct pump adapter on those. There are two types, there’s
Presta and a Schrader, which is also known as car valve. Now this particular one is
threaded all the way down, but it’s quite common to find these with a black rubber stem and just simply have threads on the top with a black cap to squeeze in place. But more commonly, on tubeless tires, you see the Presta design. The Presta valve itself
has a few components to it. It has the valve stem,
it has the valve nut which holds it in place, it has the valve coil which
is actually removable, and then within the coil on the end, it has the captive nut which tightens, meaning air can’t go in or out, and loosens, meaning air can go in. And when you press it or depress it, then the air can come out. As you can see when I do this, you can see it moving on the inside there. Now this, fundamentally, is the thing that can create problems. If you’re running a bike tubeless, then these can get gunked up. The tubeless sealant can
block up the main valve stem and actually stop this and congeal it, much like blood does, which is really how a
tubeless sealant works. It can actually bung this up enough that you can get pressure through it, but very, very slowly. And quite often, when you’re pumping, because there’s such resistance for that air to get through this, the actual head of the pump can pop off the valve altogether. Now the solution is to take these out from time to time and clean them. So if you just take the
valve core out of the stem and clean that in some hot water, and then any rubber bits you
can see, you can pull them off. Alternatively, you can get, they’re quite hard to get but you can get, these as separate pieces. And it’s always worth, when
you have old inner tubes, taking off the valve cores, keeping them. And the same goes for Schrader ones. You can also remove the
coils from Schrader valves, but you don’t need to do that as often as you would with one of these. Now the other thing of
course with these is, if you’re the ham-fisted type, they’re very easy to damage. Because as you can see, the nut itself, what it screws onto there is very thin, and if you bump that, it’s actually never gonna
sit in there correctly. And what that means is,
sometimes it’s gonna leak air or you’re never gonna be able to get air into it in the first place. So make sure that your valves, and your valve stems, and your valve cores are all in good working order. It’s well worth getting
a valve core removal tool like this one you can
see on the screen now. You’ll never need to get another one as long as you don’t lose it, and they work really well. Now of course, the other thing to consider is the pump itself that you’re using. Now pumps all have a different
chuck or a head on them, but most modern pumps, you’ll find that you won’t
have to change anything. They’ll actually include
Presta and Schrader. But even then, it’s really important how you put them onto them. You have to unscrew the captive
nut on top of the valve, and you make sure you push it fully into the actual head of the pump, and then you would engage it like so, and that means that air
will come through there. (air hissing) And just to demonstrate, if
I close that captive nut, you will see that air
will not go through there. So you’re gonna be struggling,
gettin’ air through that. And also just to demonstrate,
if it’s a tiny bit open, this would simulate if
it’s got a blockage, you’re gonna see that air
will pass through here, but there’ll be a lot of resistance to it. See, I can actually compress that, I can hear it comin’ out, but it’s actually really strugglin’. That’s the same effect if it’s blocked up. Next question is another air related one. Why do tubeless wheels
leak/lose pressure overnight? Okay, so there’s quite a lot of different factors in a tubeless wheel. So the first thing you
need to make sure of is that your tires themselves
are tubeless-ready, which means they’re compatible to be set up tubeless in the first place. So if you’ve got a standard
tire that’s non-tubeless ready, you’ll find that there’s an actual slight open-weave to that tire. Now you probably won’t
be able to see this, but it will be there. And although it is possible
to set them up tubeless, they will leak quite often
as the air just goes through. It’s a permeated fabric basically, it will come through there. Tubeless-ready tires
basically seal on the inside of the actual tire carcass and it’s ready to be compatible with a rim that has also been made
ready for tubeless. So if you start with that
and you got a decent tire, then first things first, it’s gonna work. The second thing is to make sure that that tire is seated properly on the rim. Of course in order to do that, one of the best little tricks to do is get some warm, soapy water, spread it all the way around the rim, all the way around the tire. And when you pump it up, the actual water allows it to slide into
place and the beads can lock into those beadlock areas of that rim. Of course it’s absolutely crucial for that seal to happen all the way around because that’s what, A: keeps
the tire on the rim and, B: what keeps the air in the tire. Next up is the inside of that rim. So most rims have holes
all the way around the rim in which the spoke nipple sits. And then the spoke goes into nipple, it’s basically like a bolt onto a nut, and tightens up, pulling the wheel tight. Now obviously air will leak
through those big holes, so you have to seal up those holes. Now there are certain rim
designs out there available that have a completely sealed rim bed. And of course, with that design, you don’t need to seal them up because they’re designed to be
set up tubeless as they are. For the rest of ’em, you’ll
be using something like this, some sort of tubeless sealing tape, which does the job of sealing
off the rim bed completely and making it like a
tubeless-compatible rim. But of course, it’s absolutely crucial for the rim to be completely clean and dry when you apply this in the first place, and that you’ve actually
covered all those holes and it’s taken grip. Because if any of that sealant
finds its way underneath, creates moisture, creates bubbles, then there’s somewhere for
that air to get in and get out. And then finally,
there’s the valve itself. Now the valve has to be mounted correctly in the first place,
and the valve has to be the right shape for your
particular rim as well. Now if I just take the
little rubber O-ring off, if you look at this portion of valve, if you imagine the inside of the rim bed will be slightly concave. The idea of this shape
is it sits into that. Now there are a bunch of
different valve stems available that suit different rim profiles. So it is important when you buy yours, to factor in if they’re actually gonna be compatible with your rim. Now it’s crucial that your valve stems fit your rims perfectly. ‘Cause if they don’t, you’re gonna get some kind of slow puncture or you might not even get them inflated correctly in the first place. Okay and the final one, which is one that’s actually been comin’ up loads at the moment, especially after Dakotah Norton and Rachel Atherton both
snapped their chains out the start gate of Fort William is, why do chains snap? Okay, so let’s take a look
at the humble chain here, just so you can understand the parts of it and the things that
are likely to go wrong. So look at it in profile. You’ve got outer links here, then you’ve got the inner links, you’ve got the rollers, which are the bits in
the very middle there, and you’ve got the pins
that drive through them. Now the first thing that
can make a chain snap is if the pin itself
that runs through them has become slightly dislodged
from the outer plate. Now you might not even
notice this visually, but you can have an
inspection on your chain. And you can see from
the top if any of those is likely to be slightly
further apart than the others. If there’s daylight between any of those male and female links or
the inner and outer plates, you’re actually gonna see that that will be where it’s gonna break. Now this is why it’s important to inspect your chain from time to time and why I always say, when you’re washing and
lubricating your bike, to look at every single
link on the way past. A good way to do that on modern chains is to look where the master link is and follow it a complete
revolution back to there. That gives you a reference for looking at the entire chain all the way around. Now chains do wear and you do find that chains stretch out with time. Now you can get a chain wear tool. If you’re running a chain that’s very stretchy and very old, it’s more likely that
the pins can become loose in those outer plates and then later snap. So if you’re running a
chain that is knackered, chances are, at some
point it’s gonna snap. So you have to be very
careful of this sort of thing. Chain maintenance is crucial. And when you have to rejoin a chain, if you do break one, make sure
you do it in a correct way. Now it used to be very easy
usin’ a chain splitting tool to just rejoin these in
the existing pin in there, but it’s actually not the
best way to do it these days because of the way the
chains have advanced. Now with Shimano chains
you can use a dedicated master link which they supply. Or you can use the Shimano pins. Now they’ve dedicate pins
for rejoining a chain, and although this is a
SRAM chain I’m holding, I just wanna show you the process of this. So you would join the chain
back together manually, then you’d get the pin
and push it into place, into that link, then using a chain tool. You would drive it through until this outer part
of the pin sits flush, then leaving this part on the inside, which we just snap off. Now the chain will be perfectly joined and it’s not gonna break at that point. It’s very slightly tapered, which is of course designed to sit into that outer plate. There’s two other important factors to take into account with breaking chains. Now the first one is something that all cyclists should be good at, and that’s changing gear correctly. Alright, you shouldn’t be
stamping on those gears and changing gear at the same time, your chain being wrenched
sideways across gears. Especially now with so many gears, there’s quite a lot of
stress on that chain. It’s hardly surprising you can actually pull one apart and those links can actually split open and snap. You just have to really
consider when you change gear. Even the best sprinters,
they don’t change gear as it’s got full-load on there. You might see them powerin’ out the saddle and changing gear, but fractionally, just as they change gear, they’ll just release it up on the pedals just for that split
second and then carry on as the gear has already changed. And of course you also
need to choose your timing. Don’t expect to be able to change gear goin’ up a really, really steep, slow hill and just change into an easier gear. You have to do the same thing, lurch ahead slightly,
just so you can back off on the pedals very slightly
as you change gear. It’s really, really important to do that in order to maintain your drive train, make sure it continues workin’, of course doesn’t stress that chain. And of course the last one
is ensuring that your chain is the correct length in the first place. If your chain is, let’s just
say you snap your chain, you’ve had to rejoin it with a couple of links removed
because they were damaged, make sure you don’t use your lowest gear, or the biggest physical gear, because that’s gonna put
additional load onto your chain, especially if you have a
rear suspension bicycle. At the first opportunity, you should try and replace those links, or if you need to, replace the chains, get it back to the correct length so you can use all your gears without additionally stressing everything. So there we go, there’s a
few of the common questions we seem to get here at Ask GMBN Tech. I will be puttin’ some more of those on, including that common question about the long fork on a bike. We’re gonna look at all
these sort of things in a future video. So make sure you get your questions in. Again, we wanna make sure
we emphasize the point, this video’s all about those common questions we get a lot of. So hopefully this has answered
some of those questions. If you wanna know a bit more about some of this stuff in depth, click down there for Tubeless 101. So that’s a detailed video
on everything about tubeless. The difference in the tires, how to tape up a rim, how to inflate them, how to do the dry run
like I told you about, it’s the whole lot. That is the video for you. And if you wanna know how
to join a chain three ways, click up here. So that’s basically using a master link, using the Shimano pin, and using the chain tool, which of course is a get you home version of how you should join a chain. But of course, a chain tool is included on a lot of multi-tools,
so it’s very valid. As always, click on the round globe to subscribe to the channel. We’ve got great content for you every single week here at GMBN Tech. And if you found this video
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