- The GCN Tech Clinic gets loads
of questions all about freehubs.
So I thought it's about time we actually go through exactly
what they are and how they work.
(whooshing)
(lighthearted music)
(different freehubs spinning)
Now the purpose or job of the freehub is not just
to actually carry your cluster of sprockets.
It is in fact to allow you to transfer
the power from your legs
through to the rear wheel to drive you forward
and importantly an added feature of it
is to allow you to freewheel too.
Which is pretty important let's face it.
Now a freehub isn't actually permanently attached
onto the actual hub shell of your wheel.
Instead they're normally held in place via the axle.
So you can simply slide them on or off.
Although it's not always that easy.
In some cases it is
because you can just pop off the end caps.
But on other ones you actually just have
to put a couple of 5 mm Allen keys in
or maybe a 17 mm open ended spanner,
undo them and then you can slide off that freehub body.
If you're unsure about it,
do check the manufacturer's website
because normally you'll get quite comprehensive
technical guides on there.
However, one thing certainly to bare in mind
is when you do remove the freehub
from the actual hub shell itself,
is to do it very slowly and normally over a surface
where you're not gonna lose anything.
Because well, you'll see quite soon exactly why.
(freehub spinning)
Now some freehubs are totally sealed
and can't be serviced or maintained in any way.
So generally those are found on wheels
like some Shimano, some older Fulcrums
or low end Campagnolo that sort of thing.
However, in the past I have actually taken them off
of a hub, dumped them into a vat of oil
for a couple of weeks, taken them back out
and they've worked okay.
But only temporarily so if you do have one,
really I'd save all of that fuss
and just go out and buy a new one.
First up then, let's have a look at
how a three or four pawl mechanism works.
This one on this Vision is a three pawl.
So here we've got them, one, two and three.
Sometimes you get a four or a six even
and they just evenly spaced out around the edges there.
Now these ones are actually held in place
there's a little snap ring around
the edge of the actual freehub here.
If I lift that up it means I can actually take
those pawls out and I can actually service them,
remove any of that dirt in there.
Sometimes, these pawls are held in place just simply
with little springs, tiny, tiny, little springs.
Now that's why it's important not to lose any
because they're so small, it's unlikely you'll find them
if you go on your carpet or something.
So, the way they work is they're angled
in such a way that they match up
with the inside of the actual hub shell here.
So they're almost like a reverse angle of it.
So that when they slot in, when you're driving
and the power, it drives the hub around.
And likewise when you freewheel
they're able to actually just flop back into position
and that's what makes that tickety-tick noise
inside of a hub.
(ticking)
So I just though I'd show off this design too.
So likewise it is a three pawl mechanism
but has exploded, it's nicely cut away.
So we can actually show what's going on here.
So we've got the three pawls on
the freehub here on the rear
and they're held in place, like I said before
with tiny little springs as well as a retaining ring.
But then interestingly on this hub
you've got 12 little notches on each pawl
and then inside the actual hub shell here,
pressed into place, is a ring.
So it's like a drive ring almost for these pawls to sit in
and there you've got 120 different points of engagement.
So each one has got 12, so you've got 36 points
which you're gonna be engaging all at the same time.
On well, 36 out of 120 of the little slots inside.
Now compared to the 24 inside of that Vision
it may well sound like this is the ultimate hub.
But well, you're not actually gonna get any benefits really
or performance increases in my opinion from that.
But one thing it has got, listen to this noise.
(freehub clicking)
Pretty cool.
We do a full three hub sound test later on though.
(freehub clicking)
(freehub spinning)
Now Mavic wheels they work different again.
Although some of the newer ones they work fairly similarly
to the DT Swiss ones but this one on this Aksium wheel.
I'm gonna take it off very carefully
and you'll see why, hopefully nothing comes off.
But they work almost in a reverse way
of that first freehub set up that we looked at
so the three or four pawl mechanism.
So these ones are actually attached onto
the hub body or axle almost, of the hub.
And held in place again with tiny, little springs there
and those little pawls, they actually engage
into the slots inside of the freehub body.
So just like I said at the start
they work almost in reverse
And then obviously when they engage with those slots inside
of the freehub body it's the spring tension
of these tiny, little springs that always amazes me,
that they can just pop essentially all of
the power from your legs back
into place to drive you forward.
It's amazing that.
(freehub spinning)
The next up is another type of ratchet mechanism.
This one is found inside of DT Swiss hubs
and other hubs which use their patent for it.
So first up we'll remove the end cap.
It doesn't normally come off as easy as that.
I have had to just give it a little bit of persuasion.
Then once we take off the freehub,
you'll see there is some little serrations inside of there.
Now, we've got a little spring,
then, we've got two of what DT Swiss call star ratchets.
And while one of them sits inside of
the actual hub shell here, inside there.
You can just about see we've got ourselves
some little slots there for them to actually go in
and likewise inside of that freehub body.
Then this is where the magic really works.
It's almost like a clutch plate style
so similar to have you'd have in a car
if you took apart the clutch.
So you can see here that these star ratchets,
they're serrated on one side
and then on the other side perfectly flat.
That means that when one of them goes inside
of the freehub it has the flat part against
the bearing on the inside.
First of all though you need to put a little spring
inside of there 'cause that does in fact aid engaging
and disengaging of the freehub mechanism
with the actual hub body itself.
Then you would have these serrations
line up against one another.
So if you imagine this is inside of the hub shell.
That's exactly what it's doing, so it's engaging
(clicking)
and disengaging.
So as you can see here that'd be engaging,
so pedalling travel forward as you freehub,
(clicking)
the hub will be turning and that's what's giving you
that cool sounding noise.
Now a real advantage of this I think,
is that you've got so many different contact points here.
Instead of having a three or four pawl mechanism
where you're only gonna have those bits engaged.
Here, well we've got 36 different engagement points
all at the same time.
(clicking)
(freehub spinning)
Now another set up which is pretty similar
to that of DT Swiss is this of Chris King,
which will be a familiar name to many of you out there.
Now this freehub style operates in such a way
that the more pressure or more force that you're applying,
the tighter the engagement becomes
and I guess there's some physics in there too
which means the more the power transfer
you're gonna get out of it.
Now I didn't take this one apart
because it is made of quite a few complex bits
but hopefully the images on screen right now
show exactly how it works.
And well it does give you a pretty cool sound,
'cause it's got 72 points of engagement inside.
(freehub spinning)
Now there are dozens and dozens of different freehub types
and we can't cover them all off
but finally let's touch on the axle clutch technology
found inside of some zipp-hubs.
This uses the force of magnets, that's right magnets.
So, inside of the actual hub shell here
just underneath this dust cap cover.
We can get to a 36 tooth and ratchet mechanism.
So the six magnets that engage fully
when you apply pressure through your pedals
onto that freehub and then
when you don't apply any pressure
when you're freewheeling they disengage totally
meaning that's right, that essentially you should be able
to freewheel just a little bit further
because you don't have the added resistance of any pawls
or ratchets that are clicking into place as much.
Nice little idea that.
(clicking)
(different freehubs spinning)
The noise or sound of a freehub is often talked
about recently because people seem
to desire a different sound from what's standard.
One of the suggestions to get a slightly noisier
for a loud old click is to strip out all
that lubricant and grease from these parts
as well as stretching the springs
to try and get them to snap a little bit quicker into place
to give you that loud old noise.
And then on the flip side to try
and quieten them down, people packing them full of grease
and then really compressing those springs
they don't tend to well, pop back into place quite as much
and even removing retaining rings if you've got them.
Now don't do this.
The reason being it could well turn your bike
into a fixed wheel because it won't have a return mechanism
so not allowing you to freewheel.
Then on the flip side, they become stuck down in place
meaning that the freehub turns
but it doesn't engage with the actual hub shell
to drive you forward.
There are some upgrades being made though.
Such as with DT Swiss
they actually have replacement ratchets.
So those star ratchets you can get them
with up to 54 teeth of engagement
that would give you a louder freehub.
And there are other alternatives out there.
So that is the only time I would ever
advise doing something like that to the internal.
It should be a freehub mechanism.
There we are the humble freehub.
A part of the bike which many of us often forget about
but it does a very important job.
Let me know, what you would like me to show you next,
exactly how it works from a bicycle.
Because I love getting down to the nitty gritty
of these components.
Get involved in the comments down below.
And also remember to like and share it with your friends.
Share it with someone who wants a really loud freehub
to warn them of the dangers of doing that
because Johnny Text told them.
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