- In our weekly Ask GMBN Tech show,
we get hundreds an hundreds of questions from you lot.
Now, there's always a pattern
of certain questions coming up quite frequently,
and in the past, we've done some commonly asked questions,
so here are five more commonly asked
mountain bike tech questions.
Okay, so a really common question actually,
and it's a strange question to be a common one,
is does it matter which way up my rear shock is?
Now of course there is a typical way
that you would have a shock on a bike,
but quite often you do see bikes
with shocks flipped, or the abnormal way.
So, technically on a bit of paper,
it will not affect the performance of the shock,
which ultimately is what a lot of you are worried about.
But, you've only gotta think
that some manufacturers actually spec their bikes
with the shocks in a different position
to what you would determine as normal.
And what I mean by that is,
if your shock is in a vertical position on the bike,
you would assume that this is the logical position.
The main reason for that is you got the adjusters
at the top, which means they're easier to reach
whilst you're riding.
But some bikes like Scott Genius, for example,
the shock actually comes flipped like that, or inverted.
Now, one of the concerns might be
that you'll get mud, and the water, and dirt and stuff,
on the top of what's effectively the stanchion tube.
But it's effectively just the same
as a suspension fork, that's in the same position.
And if anything, and there's far less to worry about
with the shock than there is with the suspension fork.
Suspension forks operate at low pressures.
The seals on them are quite simple
in comparison to these.
These actually have two rows of seals.
They're very tight fitting,
and the lubrication sits just on the inside here.
So actually, you get far less of a problem
with a shock inverted from that respect,
than you would with an equivalent suspension fork,
and of course, all suspension forks really,
apart from some inverted downhill options,
and the odd single crown,
are of course this way up.
So, that is not a problem, and,
in case you're wondering why Scott chose
to mount theirs this way up,
it's because they have a lockout system on their shock,
but it's operated by a remote and the handlebars,
and otherwise you would have the cables poking out
into the middle of the bike,
and it'd be a right odd mess.
So they route them down through the downtube,
and up to the bars, so it's very neat and simple,
and of course, you don't actually need
to access this part of the bike.
Once you've setup your air pressure, it's all in place.
So it actually makes no difference,
physically when you're riding the bike.
The difference it makes is just
in order to facilitate getting to the actual adjusters.
Now that is something that is worth talking about.
If you fancied flipping the shock on your bike,
there are a number of factors you need to take into account.
The first one is that there is adequate clearance,
depending on how the shock is mounted at either end,
because you could, under compression,
shocks move, and they alter their positions,
depending if it's a floating mount, front and rear,
or if it's a single pivot,
it moves pretty much just from the rear,
and will pivot slightly at the front there.
Now, you gotta make sure that there's no chance
it can foul on any part of your frame,
because it will damage your frame,
and it will damage the shock itself.
So there's usually a reason why manufacturers
put the shocks in that position.
Another thing to factor in is,
if your shock design has a piggyback reservoir on it.
This particular one doesn't,
but piggybacks sit down here,
and sometimes manufacturers have to flip the shock
into a different position,
in order to allow enough room
for where the piggyback sits in the frame.
For example, if they wanted to have a water bottle
in the frame, or if another particular part
of the frame design would clash with it.
That's the only reason you see them flipped around.
Really, it's all about the convenience
of accessing your adjusters.
Okay, another question that does come up,
which actually I'm surprised a lot of people ask this,
is does it matter which gear you store your bike in?
Well there's a few schools of thought on this,
and the logical one really,
would suggest that you store your bike
in the highest gear possible.
Certainly, if you got a one-by setup,
the highest gear meaning you're int he smallest sprocket,
so the derailleur is under the least amount
of tension possible.
And also, the cable is under the least tension.
However, I don't believe that storing a bike
in say mid, or one of the higher gears,
will actually affect cable tension,
because you use way more cable tension
when you're actively changing gear,
than when the bike is just stored in that setting.
And, I know for a fact
that I've got several bikes in storage
that have been, some of them since 2011,
literally have not been ridden,
and they'll be stored in any random gear.
And I'm even tempted to go and get one to prove it,
the fact that I can take it out of my loft,
I could pump the tires up,
which of course over time do deflate themselves,
and prove the fact that the gears still work fine.
Now, the spring itself though,
that's an interesting point to consider.
So the spring, yeah, I guess you could, in time,
given how much a spring has to actually stretch,
each time you change gear,
if you stored it in that setting,
arguably it could be fractionally stretching that spring.
But really, with a derailleur on a mountain bike,
I would say this is not a concern at all,
because you're gonna wear out the jockey wheels,
you're gonna bend the jockey cage,
and probably smash the rear mech off,
long before that ever happens.
It might, however, be a consideration
on an urban bike, commuter bike, a road bike,
something like that.
But you'd have to be storing the bike
for a pretty long time, I would think,
to have that effect.
Okay, now here's a classic one.
Does storing your bike upright,
like in the vertical position,
let air into your brake system?
No, this is a myth.
If you have air in your brakes,
this might help expose that fact,
but it certainly won't introduce air into your system.
Especially if your brakes have been bled correctly
in the first place.
I store all of my bikes vertically at home.
Some nose up, some tail up,
and in our lockup downstairs, and in the workshop,
we also store our bikes vertically.
There is no problem with this.
Now, some brakes are more prone to developing air bubbles
in the system than others.
There are some problematic brakes on the market.
Over time, certain types of brake oil, like DOT oil,
can absorb microscopic amounts of water into the system,
which can affect things.
And over time, you might find
that you do need to bleed your brakes,
just because of seals perishing,
and air getting into the system.
Now when you store your bike upright,
what you're actually effectively doing,
is allowing that air to migrate to the top,
to your lever end.
So, if you have got air in your system,
and you've been storing your bike upright,
chances are, get your bike down on the floor,
go to feel your brakes,
and they might sort of pu-
you need to pump them a couple of times
before you get to use them,
and that's because the air is at that top.
Now if that's something that you have
with your own brakes, then really,
the best thing to do is give them a full system bleed.
Bleeding brakes will always remedy this problem.
However, if you want a quick, lazy way around this,
something that is quite cool,
and quite easy to do, is basically pull your brake lever,
and use a toe strap, or something similar, cable tie,
to hold your brake lever in the locked position.
Store your bike upright overnight,
and those air bubbles will migrate
straight to the top there,
and at which point, you can undo your master cylinder cap
on the top, and basically get those air bubbles
out the system.
Now I've heard of some people doing this before,
and actually loosening off the bolts there
on the top of the lever, on the reservoir there,
in order for those air bubbles
to migrate out by themselves.
And if necessary, you can top up with a bit of fluid
in there and replace the cap.
That's quite a cool way around things,
but nothing will beat doing a full system re-bleed.
Now it might sound like a daunting thing to do,
but it's really, really quite simple.
You just need a few specific tools.
You're gonna need the oil that's suitable for your brakes.
Of course some brakes have mineral oil,
and some have DOT oil, and you cannot mix them.
Just get a new fresh one.
And also, when you're buying DOT fluid,
because of the nature of DOT fluid,
over time it can absorb moisture into the fluid itself.
It's best to only get enough
that you need per bleed, really,
because if you have a big container of it,
it might cost you less to buy the container per bleed,
but it will actually go off in time.
Mineral fluid, however, you can buy a big one of those,
and nothing happens to it.
It will not absorb water into the system in the same way.
So really, don't be afraid if there's air in your system.
Get yourself a bleed kit.
There's plenty of places you can get them online.
They don't cost a lot of money,
and really it's a fairly simple process to follow.
Only a few steps up from bleeding a radiator in a house.
Nice and simple,
and your brakes will feel fantastic afterwards.
Now this is a classic.
Do chains actually stretch?
Yes and no.
So, they don't stretch in the sense
that you would actually think these links
become longer and stretch.
That just doesn't happen.
However, what does happen,
is the pitch of the chain will stretch slightly,
and what happens when that does occur,
is the fact that your chain,
not only is it worn and become sloppy,
it actually wears other components in your transmission.
Like the chainring teeth, the troughs,
and the actual shape of the teeth profile themselves,
and the cassette out back.
And of course, when that happens,
it means you have to replace them as well as the chain,
which is why it's so important
to get yourself, even a basic version of one of these,
a chain checker.
Now the reason for that,
is you can check, you can monitor the wear,
and the stretch on your chain, and the pitch itself.
So, as soon as your chain is starting
to show signs of wear, you wanna be replacing it,
because then you won't need to replace
the sprockets, or the chainring up front.
Now let me just explain the process of this,
and how it works.
So, a chain is made up of a few components.
So you've got the main links,
so these are the outer links,
and you've got the inner links.
Then you have the pins that run through the middle,
holding them together,
and then you have the rollers.
So, these are the pins.
These are the rollers in the links.
And the outer links.
Now, as part of those inner links,
there is actually a bit of bush system here,
so the roller can actually rotate around it.
And then the pin goes through the middle,
basically holding the whole system together.
Now what happens over time with your chain,
especially under high load, or lots of miles,
or really bad weather conditions when you're riding,
is the rollers actually develop play,
as the bush that they rotate on slowly become baggy.
And effectively, everything starts moving internally.
So the plates themselves will not grow,
but you will get stretch of the chain pitch.
Now, chain pitch refers to the length
between the two pins.
Now the pins is half inch between them.
So, basically when you have a chain tool,
it will tell you measurements,
like this one, for example here,
says new chain is .25 to .5,
and replace it at .75.
So, I would actually go as far as changing it
when it's just over .5, really.
But it does vary on how much money you have,
and how often you ride in bad conditions,
how strong your legs are,
a whole number of different factors.
But the point is, when your chain starts getting baggy,
it's not gonna connect well with the transmission.
It's gonna wear out the other components
in your transmission.
It's not gonna shift very well either.
This one here has some sort of movement to it,
but that gets really accentuated
the more worn the chain gets.
So, technically yes, a chain does stretch,
but no, the links do not actually physically get longer.
Now this one makes me laugh, actually,
because this is such an obvious question.
It is, why is dry lube actually wet?
Yeah, okay, so lubes a lube, really, are they?
No, not so.
So you get two main types of lube.
Of course there are loads on the market.
You get ceramic lube, suspension lubes, Teflon lubes, etc.,
but fundamentally when it comes to chain lubes,
you'll get a wet lube, and you'll get a dry lube.
Ultimately, with dry lube,
the wet bit of it is just a solvent.
So, this is effectively a carrier
for the lubricating particles,
in order, when you lube your chain,
to make sure that those particles get
into the inside of the rollers.
That is what you need to lube on a chain.
Don't need to lube the plates.
Don't need to lube anything else, just the rollers.
They're the bit that need the lubrication.
So, ergo, with a dry type lube,
you need a solvent in order to soak into there,
and then the solvent dries up,
hence the dry lubricant.
Now, dry lube actually is very, very good,
despite the dry name.
But the only downside really,
is the fact that you do need to apply it more frequently,
because it doesn't have the kind
of viscous sort of stickiness to it, to keep it in place.
Very good for hot, dry conditions.
Not so good for wet British conditions,
although I actually favor a dry lubricant all year round,
on most of my bikes,
just because I'm always cleaning my bikes,
I'm always maintaining the transmission.
But of course, that is not the case
with a lot of riders.
Now wet lubes clearly are designed for use
in wet conditions, and the way it differs
to a dry lubricant itself is,
it has the same lubricating particles,
except it's in a really thick, viscous liquid.
Now the idea for this, is you can put it on,
and it stays on a lot longer.
It's quite waterproof.
Some are more waterproof than others,
which can mean cleaning your chain
with wet lubes on.
Bit more of a task.
And of course it will draw a sticky, horrible mess to it.
If you use this in summer conditions,
you'll have dirt and grit all over your transmission.
It quickly turns into horrible black sludgy stuff.
However, as far as an actual lubricant goes,
wet lube is fantastic.
So there you go, there's effectively two types
of lubricant for different conditions.
But if you wanna know a bit more
about the other types of lubricants out there,
and in fact, any sort of assembly compounds,
greases, threadlocks, and stuff like that,
check out the video I'm gonna put
in the link below this one.
I've got a whole video that tells you exactly
where you should be using this sort of stuff,
the conditions you should use it,
and where you should apply it.
So there we go.
There are some very common maintenance questions
that you guys fire into us.
If you got anymore questions,
let us know in those comments below,
or you can send them into HelloTech@GMBN.com,
email address on the screen there.
For a couple of videos along the same lines,
click at the bottom there,
and you can see both of the previous videos
with five common maintenance questions.
As always, don't forget to give us a huge thumbs up,
and don't forget to click that Subscribe button.





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