Freehubs Explained: Everything You Need To Know About Road Bike Freehubs

Freehubs Explained: Everything You Need To Know About Road Bike Freehubs


– 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. Now remember to check out the GCN shop at shop.globalcyclingnetwork.com we’ve got a whole heap of goodies. And now for two more great
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