Across the varied shows
that we have here on GMBN Tech,
there's a lot of terminology and confusing tech terms used,
in particular with things like suspension.
So what we're going to be doing today
is taking you through a whole bunch of the more common
suspension tech terms and explaining to you
exactly what they are and how the affect your bike.
So, first up is compression.
Now this refers to the way damping is controlled
on a shock or a fork, for example,
specifically the way it's controlled when it compresses.
The adjustment for compression is usually
a blue dial or a switch.
Now those with switches tend to offer two to three
positions with variations on what they do,
which tends to be open, mid, and locked.
The typical compression adjustment you do externally
on a shock with these dials or these levers,
affects the low speed compression of the shock.
Now the low speed compression adjustment
can effectively be used to keep the bike more balanced.
So, for example, under braking with no low-speed damping,
the forks are naturally gonna want to dive,
and that's weight transfer.
That's what happens.
But by adding some low-speed compression,
you can effectively hold the front end up
so it resists that dive,
because that's movement at low speed,
that's how that damping works.
And the same, if you flip this and talk about
the back end of the bike,
when you put low-speed compression on the bike,
it's gonna resist the bobbing that happens.
Now, bobbing happens for various reasons
which we're gonna get into in another part of this video,
but if it's weight related for your body weight
and the sort of oscillation you get
from pedaling up and down,
you can actually resist that by adding
some low-speed compression and effectively
it stands up and will make your
bike feel like it climbs better.
So, just to summarize,
with low-speed compression damping,
less low-speed compression damping,
that will equate to a bike that feels
very active and very supple under
all sorts of suspension actions.
However, it's going to be more affected by
your body weight and how you ride that bike,
so by having more compression,
more low-speed compression on that,
you're gonna be able to stand the bike up
and make it less reactive to what's
going on with your body weight.
Now, high-speed compression damping,
of course is the complete opposite.
This is all about when the shock shaft
or the fork itself is traveling extremely fast.
So, that suggests it's from a big impact or a fast impact,
something like bombing it down a trail flat out
and you're hitting rocks and roots and stuff,
that's when the shock or the fork's
really traveling through stuff,
and you need high-speed compression damping
in order to control that and tame that.
Less high-speed compression damping will mean
your shock will feel slightly smoother,
perhaps a little bit more linear, not necessarily true,
but it will feel a little bit more linear,
you will use that travel more often,
but you're more likely to bottom out
at the end of that travel.
More high-speed damping can feel
overdamped and very, very harsh,
and to a degree you might not use all of that travel,
so it's a fine balance to get to.
Rebound is something that refers to
the damping on a fork or a shock,
specifically the controlled movement
of the shock or fork extending,
so returning from full compression.
With less rebound it's gonna be faster,
with more rebound it's gonna be slow.
Now normally, there's just a single adjuster
which will be a dial or knob of some kind
for adjusting rebound damping.
Now, there will have notches on there so you can return
any amount of clicks you need to dial in.
Now, it's directly proportional,
the way you adjust rebound damping,
in comparison to the air springs,
so a heavier rider such as myself
will need to have more rebound damping
in order to control that,
because it's got more air pressure
in there in the first place,
whereas a lighter rider will probably have
far less clicks of rebound to tame it,
to make it feel the same.
Now, although there's no right or wrong,
when it comes to rebound damping
you do have to get some things right.
Now, if you have too much damping on there,
it's gonna be really slow and feel really harsh,
the shock will barely return in time
before the next hit, and it will stop packing,
which is when it gets bogged down is it's
basically having to deal with repeated hits,
and it's not extending in order to cope with those,
so that is a bad situation to be in.
But likely, it's just as bad to have too little
rebound damping on there and you can end up on a pogo stick.
Now it might feel really nice when you're just
coasting through something with,
let's say roots, loads of small bumps,
because the wheel can track the ground really nicely,
but as soon as you start hitting stuff hard,
it's not gonna be able to control what's going on there,
and to an extent, you can find yourself ricocheted
off the front of the bike if you don't have
enough rebound damping applied to control that.
Next up is lockout.
Now it's quite a simplistic term,
and all it means is you're locking out
the suspension from compressing,
so you're stopping it working, basically.
Now lockout is the sort of thing
that you're gonna want on your bike,
for example if you ride up hills quite a lot,
you don't want suspension to be bobbing around
to your body weight so you whack that lockout on.
Now, on the inside of the shock absorber,
there are a system of shims that the oil flows through,
and the shims have different size holes in them.
Bigger holes enable the oil to flow through faster,
smaller holes will flow through slower,
and when you close the holes the oil can't flow at all.
That really is the fundamentals
of how a lockout system works.
Positive and negative air springs, or air chambers.
Now, every air-sprung fork has a way
of putting air into the fork to give it a spring weight
so it's sprung to your body weight.
Now, this is the positive chamber,
so that is to support your body weight.
Now, a lot of forks used to have a negative spring,
which was a coil spring,
and the essential is basically to preload that air spring.
And the reason for that is air,
when it's in a compressed space like that,
you have to overcome the initial
resistance of that before it starts moving,
so a typical air spring with no negative spring
will feel very harsh over small stuff,
and to some degrees won't even work that well.
Once it gets moving, you're okay, it's moving.
So what you do is you have a negative spring
to apply a preload to that,
enable it to feel nice and supple from the bottom.
Now, most modern shocks and forks will have
an air negative spring in there.
Now, the air spring itself,
they tend to be self-equalizing,
so there'll be an air port on the inside,
and depending on the model of your fork or shock,
when you pressurize them you'll have to do
a certain thing like maybe compress it five times
in order for the air to transfer in the transfer port
from the positive to charge that negative chamber.
So the negative air spring is effectively just
a preload on the positive air spring,
and the effect of that is you get a really minimal
breakaway force so you're not having
to fight that positive air chamber,
and really, it means that the shock or the fork
is gonna feel a lot more like a coil spring,
which are known for being very supple from the very
beginning of the travel all the way through the travel.
Pedalbob.
Now pedalbob is the sensation you get,
essentially from your body weight when you're pedaling.
Hence the name pedalbob,
always happens when you're pedaling along,
but more oft than not it tends to be like
an oscillation of your body weight
that has a direct affect on the bike, bobbing slightly.
Now, we're only talking five to ten millimeters,
but it's enough that it can rob energy
because your energy that should be going to the pedals
is turning into up and down movement at that shock.
Now, some suspensions designs will resist
bob or squat from pedaling a lot more than others,
and they're the designs that tend
to have a higher anti-squat value.
As far as the actual up and down bobbing goes,
if it is down to body weight,
this can be controlled using low-speed compression.
Anti-squat.
This is essentially a way around pedalbob,
and it's pretty much a determining factor between bike
designs of how some bikes will pedal better than others.
When you pedal a suspension bike,
it can have pedal squat.
Ant-squat is simply the value to counteract that.
For example, a bike with 100% ant-squat value
effectively means you're cancelling out any squat,
so you won't get any bob whatsoever when you pedal.
Bikes with multiple chain rings will have
different feeling and different levels of anti-squat,
depending the chain ring position,
and of course where the pivot point
is in relation to those chain rings.
But generally, the smaller chain rings
will have a higher anti-squat value,
and that's actually quite a good thing
because when you're using a small chain ring,
or the granny ring,
it tends to be in a high-torque situation,
you're really cranking to get up something steep.
So having a high anti-squat value
to keep the bike upright is actually really beneficial.
Now, whilst high anti-squat numbers
might seem really appealing,
they do have some small downsides, too.
Now, really high anti-squat for example,
when you're pedaling and putting a lot of chain tension on,
you're effectively pulling that hub down,
which means, okay great, so you're standing
the bike up quite nicely when you're pedaling,
but when you start hitting bumps,
it's gonna feel quite harsh,
and to a degree you're gonna get some kickback
in those pedals as it tries to counter those forces.
Brake Jack.
Now, this is also known as anti-rise,
and it's simply the effect that braking has
on your rear suspension that you feel at the rear wheel.
If you compress the back end of a static bike,
you might find that that disc caliper
moves in relation to the disc rotor.
Now, depending on the suspension platform you have,
it's slightly gonna move more or less.
The less movement it has, the less interference,
or the less feeling you're gonna get
at the brake lever from using the brakes
and affecting at that suspension.
The more movement it has,
the more likely you are to feel this in the suspension.
Now, the general feeling of brake jack or anti-rise
is the fact that when you're braking,
it feels like the suspension firms up slightly,
so it might feel like you have
slightly less grip at the tire.
Some people get really, really fussy
about that sort of thing,
but bear in mind that when you're
riding on very steep terrain,
riding down steep terrain,
the times that you're gonna feel brake jack--
you gotta bear in mind that most
of your weight bias is gonna be on the front brake,
so any heavy rear braking you do,
regardless of what suspension system you have,
you mean, you've got less weight on that rear wheel anyway,
so it's more likely to skip around and lose traction.
But, that said, it's also a bit of a double-edged sword,
because arguably a bike with less brake jack
is gonna have that little bit more traction
and that might be enough to keep you
from braking loose at the back end.
But like I say, really the more important thing
in this case is your body weight on the
wheel that's doing that braking.
Typically, you will see more brake jack
on single pivot bikes like an Orange Five, for example,
and you'll see less brake jack effects
on a bike like a Stumpjumper,
which has got the four-bar linkage, FSR design,
kind of similar to the Nukeproof bike I ride, actually.
Trunnion mount.
Now, this refers to a specific type of shock mount.
Now, traditionally, all shocks have eyelets,
one at each end, and you often hear
the "eye to eye measurement" that simply is
the measurement between those two eyelets.
Now, on some bike designs, for various different reasons,
you end up using a shorter shock,
and what that tends to mean is you get less room
on the inside for oil and shims and
all the other stuff leads to
that nice, consistent performance.
Now, by having a trunnion mount shock,
you effectively get a longer shock,
but it has the same eye to eye measurement,
so you've got more stuff going on on the inside essentially.
And basically the bolts will mount
directly to the shock rather than mount
into an eyelet that's on the top.
A pretty simple system, really,
when you actually just look at it.
In the old days, GT used to use a trunnion mount
that was actually adjustable so you could
raise the height of the shock in the frame accordingly,
and drop the bottom bracket or raise it slightly,
which is quite a cool use of that trunnion mount system.
Piggyback.
Now, this is the extra little part of the shock,
like the piggyback of a shock,
and it's essentially there to offer
more consistence and performance.
It won't actually give you any more
features on a shock from a conventional body shock,
it's just designed to perform better in certain conditions.
Now, a regular shock, you've got on the inside,
keep this basic, you've got your air spring unit,
you've got the outer part of the shock,
you've got the inner body that slides in there,
you've got a damping rod,
and you've got the oil and the IFP inside there.
Now all that stuff going on on the inside
is gonna get very hot in use.
Now, heat on the inside of the shock,
you're gonna get an increase in the expansion
of the nitrogen charge just under that IFP,
and also the oil itself is gonna get very hot.
Of course, hot oil will end up running slightly thinner,
which means you start losing damping characteristics.
This is known as fade, or damping fade.
The idea of a piggyback shock is to
increase the amount of oil it has
and to move the oil in the IFP
situation outside of the main shock body,
so it's far less affected, basically.
So, it's not necessarily a better system.
It's a more consistent system in more demanding conditions.
Of course, there's extra weight,
and there's problems with fitting them
on certain bike designs,
so they're not for every system out there,
but they definitely do have more durability,
and more consistent performance when things get rowdy.
So there we go.
Hopefully some of those tech things
in relation to suspension have been answered for you.
If you've got any questions,
or you've got any more that you wanna know,
let us know and we'll do an explain on those,
but we're definitely gonna do a full, in-depth,
a really in-depth suspension feature soon,
so keep an eye out for that on GMBN Tech.
For a couple more videos, in fact ones I did over on GMBN,
click down here for finding out why you really
should be riding in really good technical clothing,
and if you want to find out how to look after that stuff,
click down here.
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