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How Things Work: The Freehub Body

How Things Work: The Freehub Body

http://mpora.com/videos/r6SP2DtVL If you’ve ever wondered what goes on inside your rear hub then check out this in depth feature…

Hopefully you should now be feeling a bit more confident to delve inside your hub and give it some love. It’s worth pointing out though that you should really take your cassette off first. Whilst you can reassemble some designs even with the cassette in place it just makes life easier if you take it off, and with other designs you have no choice so you might as well do it just to make sure. Shimano hubs and some cheaper cartridge bearing hubs have a sealed freehub design so you can’t really service these, instead they’re a case of replace when knackered.

If you didn’t quite catch some of the detail in the video, or just want a closer look at the inner workings, then here are some close up shots and even more information on all things freehub…

The ratchet and pawl system that you find inside a Hope hub is by far the most common design. The finer details may change a little between makes, but the overall principal is the same. Some use leaf springs like Hope whilst others use tiny coil springs, and some use a retaining ring to hold everything in place whilst others (annoyingly) don’t bother at all and those ones are a little more fiddly to put back together…but you can do it!
The number of pawls can also vary between designs, but in general the more the better. To produce a faster pick-up some companies also offset the pawls so as to double the number of engagements per revolution. So you might have six pawls but only three are actually engaged at any one time.

The ‘ratchet’ part of the ratchet and pawl system. Big teeth and pawls will deal better with larger amounts of torque, but on the other hand a finer set up will give you faster engagement. Like so many other parts of a bike it’s a balancing act, and that’s why as I said before several companies have chosen to go down the offset pawl route rather than making things finer.

This Halo Supadrive design (which is also used by other companies) is pretty clever. If you were to make a conventional ratchet and pawl system with 120 points of engagement then the pawls would be so fine that they would easily slip or snap. Using lots of of teeth on each pawl though means that the load is spread out over a larger surface, and these pawls slide up a little ramp and wedge securely under load. A simple rubber o-ring stops the pawls from going everywhere when you take it all apart.

As you can see the Supadrive ratchet is very fine indeed, but that’s what gives you the almost instant engagement.

DT Swiss have been using their patented Star Ratchet system for years and although it doesn’t offer the fastest engagement it’s a very reliable system which is also incredibly easy to maintain. The design’s greatest strength is its ability to cope with very high load. The reason for this is that you always have 18 points of engagement, that’s like having 18 pawls!

One of the ratchet plates sits in the splines in the freehub body and is pushed towards the other plate by the spring that you can see.

Just like this.

And then the other plate sits in splines in the main hub body and is again pushed towards its counterpart by a spring.

Thanks to this cutaway hub we can see the rarely seen inner workings of a Chris King hub. As you can see the ratchet plates are very fine compared to the DT system, and that’s what gives these hubs their ultra fast engagement. There are 72 positions rather than 18. You might think that would mean that it is more likely to slip under load, but because of the exclusive ‘RingDrive’ design the sprung ratchet plate is forced into the fixed one via an angled spline when you apply toque to the system. The harder you pedal the harder it bites. Also, because Chris King have located this system in the main hub body they’ve been able to make it a larger diameter than the DT system, which means all those teeth can be spread further apart. This system really is something special.

Here you can see the angled splines which help force the ratchet plates together under load. It’s actually very simple, but at the same time it’s highly effective and lets Chris King use a finer system than would otherwise be possible.

And finally just a little look at the other part of what makes Chris King hubs so special (and expensive). You’ll struggle to find better quality bearings anywhere, and just like the rest of their hubs these are all made in-house so you won’t find them anywhere else.

So, hopefully now you’re a little bit wiser about freehub bodies, but if you’ve got any questions then fire away and I’ll try and answer them. Oh, and if there’s anything else that you’d like to know about/want explained then let us know and we’ll try and sort it out…

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  1. bart

    that was a lot better than any tech tuesday

  2. Ed

    Somebody has just asked ‘what type of spray or grease should I use on the pawls?’, and my answer would be grease, but nothing too thick as sometimes that can make them stick, particularly in colder weather. I personally use some very slippery fork grease.

  3. Thebear


  4. Andy

    DT Swiss do a 32 tooth pick up upgrade for about £35.

    I bought it for my DT swiss 340 and was well worth the money and is really easy to fit(all you do is replace the 2 ratchet rings and your done).

  5. Euan

    Great article. Thanks =). Maybe on on the inner workings of forks? or shocks?

  6. James

    Brilliant article Ed, well done. More like this please!

  7. PN

    this is awesome. do more of this.

  8. Dom

    Yes, love it. Thanks.

  9. C Finnimore

    I love all this stuff. Marvellous, excellent, props and all that.

    Such a geek.

  10. Benner

    As per James’s comments…..Excellent work Ed. More like this please.

  11. PrematurePro

    Wow feck me that was helpful , always thought the hubs were a billion times more complicated.
    Thanks alot,

    Certainly cleaning it proper regurlarly now.

  12. goosecock

    You missed out the fact that hope pawls and ratchets are made from balsa wood. I’m off out now to buy a Chris king.

  13. sharpy182

    Quick, simple and to the point. let’s have more of these please. Tech videos that you don’t have to be a bike machanic to workout what’s going on. good work Dirt crew!

  14. craig

    That was amazing! so nice and simple, well put together! i didnt think it was that easy to service my rear hub

  15. Leo

    Any chance of a look inside a freecoaster hub? not mtb but I’m fascinated.

  16. Doc

    Always wondered why Chris Kings were so expensive, thats some amazing engineering going on there. I got brave enough to take apart my superstar hubs last year and i couldnt believe how simple they were. Makes a big difference knowing whats going on inside something when it comes to diagnosing problems on the trail when you get them.

  17. TomW

    And that is all the excuse I needed to buy Chris King hubs…!

  18. Michal

    A very clear and simplified overview of the most complex component on a bicycle. Thank you, time well spent.

  19. Morgan

    Leo, freecoaster hubs are kinda similar to the King/DT idea of two plates that are pushed together under pedaling force. However, when they’re not under load the two plates are far enough apart to not have any overlap of the teeth. That is why there is no noise at all from a freecoaster (the teeth aren’t continually clicking over each other when freewheeling). It’s also why there is a massive amount of free movement in the cranks before engagement, as the two plates have to be wound in quite far to engage.
    The more modern systems allow you to adjust this amount of free play from almost instant pick up (much harder to fakie without the plates engaging and making the cranks run backwards), or massive amounts of free play (in excess of quarter of a crank turn), which make landing fakies and roll backs much easier as the plates are much less likely to engage if you move the cranks a touch.
    Anyway, that’s my understanding of it. Could be wrong/misguided. I thin ksome companies even use uni-directional roller bearings instead (may have only been prototypes) which give infinate roll backs, but instant engaement.
    I’ve ridden a few mates bikes with them fitted and they are WEIRD to ride with, but fun once you get the hang of them

  20. Hancock

    How dampers work!
    It needs to be explained in simple terms what the difference between a platform valve and shimmed valve is and why it’s important. There’s too many people look at forks and shocks like there’s some kind of magic in there, instead of oil, tubes and a little stack of thin washers…

  21. tony Cooper

    Dirt its the best magazine-forum-site regarding mountain bike…..

    it make me feel i want to donate some money….

  22. billy

    Cheers Tony, large denomination banknotes are always welcome…you know the address;-)

  23. jimmy fids

    Good article. The only reason I run hope hubs is because they are so ridiculously simple. The Halo SupeDrives look like a real solid hub too

  24. Danners

    Really good read nice one Dirt. I want to see more like this!

  25. Oli

    May sound stupid, but can I make my Superstar freehub louder? Its brand new and is totally silent. I like a little bit of buzz like…

  26. Trevor

    Do more tech articles like this. And why no mention of Hadley hubs?

  27. Pez

    That was mint have been worrying for ages about trying to service my superstar hub but there is nothing to it! Cheers Dirt!

  28. TimBud

    That is really bloody good. Need a CK hub even more now!

  29. Hayden

    What an awesome little article and video. Quick, to the point and very simple to understand more of these please!! Thanks dirt!

  30. ddmonkey

    Thanks for that really interesting, and well explained.

  31. Grazza

    @ed, is there any special kind of lube or grease I need to use for particular systems or brands. I have a set of Mavic Crossmax that are not coasting too well. I see you use grease on the hope system but in the manual on the mavic site it recommends that mineral oil is used.

  32. churchie

    Great article, very interesting.

  33. Deano

    As my wife says im a ‘bike geek’ so I love it!

    I’ve spent some frustrating times trying to piece older spiral spring hope freehubs back together….. [breathe] and don’t chuck it across the garage!

  34. Michael

    Fantastic article and came along at just the right time for me. I was wondering why no manufacture uses one-way sprag bearings instead of the rachet system? Sprag bearings have ultra fast engagment, they may need additional shielding from dig and water but otherwise I am stuggling why nobody offers it in the bike industry. Cheers

  35. Rodney

    I’m with you Trevor. Why no mention of Hadley hubs? I run Hadley on both my bikes and my wife has ’em too. Superb fast engagement. Handmade by Mr Hadley in the USA. Hadley and Chris King make the best hubs IMO.

  36. Rodney

    By the way you Dirt guys – this tech feature is fantastic! So good I’ll forgive you not mentioning Hadley. Give us more please!

  37. billy

    @Rodney, sorry, we didn’t have a Hadley hub to hand, but we could maybe do an addition at some point.

  38. Ed

    For all you Hadley fans (and yes they do make amazing hubs) there are two reasons why we didn’t include them in this feature. Firstly we obviously couldn’t include every type of hub (and it was meant to be more of a general overview anyway, giving you a look main designs), and secondly we didn’t have one here in the office.
    As for sprag bearings Michael, yes on paper they look like they’d work well but I know that Middleburn (and possibly others) looked at using them years ago and made several prototypes but as you hinted at they really don’t like any kind of contamination. They worked a treat at first but they soon started playing up, no matter how good they tried to make the seals. Hence why they ditched the project. Maybe it’d be ok for road bikes, but for mountain bikes I think it’s a lost cause, especially because at the end of the day companies have managed to make designs that do engage almost instantly, and yet they’re far more reliable than a sprag bearing.
    Grazza, as I said in an earlier comment I personally always use a very fine suspension grease, and not too much of it. You can use oil, and it’s very good if you want the lowest drag possible (and lots of noise…Oli you could try this), but I find it doesn’t stay in place too long so you have to strip your hub fairly often. Have you checked all the bearings in your hub though cos I reckon it’s more likely that those are the cause of your drag problem. If you really want the lowest drag possible (but I wouldn’t recommend this for normal use) then you could do what a load of the World Cup boys and girls do, and that is to flush all the grease out of your hub bearings and replace it with oil. Basically though if you use a fine grease on the Mavic pawls it’ll be fine (I have done it), just don’t use anything too sticky.
    Oh, and as for a similar feature on suspension, watch this space…

  39. Ed

    Great communication between Billy and I just then!

  40. rob

    @Oli, they are probably good and packed with grease, they will get louder as the grease breaks down/gets thinner and some is displaced by the inevitable crap that will get in there. Or why not try stripping it down and having a look inside.

  41. rob

    Wasn’t showing Eds post when I posted….oops

  42. DNS

    @Michael, there is one company that uses one-way bearings rather than a ratchet. Check out the True Precision Stealth hub…http://www.trueprecisioncomponents.com/

  43. Fahzure

    King hubs are “special,” requiring special tools, special lube, special/extra service. I like the King quality, but not the complexity. DTSwiss, on the other hand, are servicable with common tools, rarely requiring it. Looking for added engagement, get the 36 tooth star ratchet.

  44. Dom

    Without wanting to sound stupid, how do i get my cassette off? Any chance of a video on that? Or am i the only idiot?

  45. Trigoc

    Full on Quality.

  46. eightdigitword

    @Dom, an idiot wouldnt ask. Once you remove the wheel and axle you will need a cassete tool and a chain whip. You are looking to slacken of the nut on the end (small gear end) of the cassette. As the cassette nut has a right hand thread (counter clock wise to remove) you use the chain whip to secure the cassette from spinning on the free hub assembly. you may need a spanner to grip the cassette tool depending on the design. Make sure you have a good grip and gently apply pressure. You will hear a cracking noise as it releases, these can be quite tight and may need some force. Be extra carefull not to over tighten when re-assembling.

    @ed, great artcle.

  47. raddog

    Fantastic article and vid. In my ignorance I had always just assumed all freehubs used a ratchet and pawl system. I feel enlightened. More articles of a similar vain would be great:)

  48. racer

    Any thoughts on the inner workings of the Mavic Deemax rear hub? I have them on my downhill bike (2011 Deemax) and would love to know how to service them. Like other people, I have been put off by the potential complexity. Maybe it isn’t so bad after all.

  49. Dave

    Great article, well explained without being patronising- nice one lads.

  50. Papa Kern

    I’m a heavy guy who kept breaking hubs. Got a set of Chris King 15 years ago and never looked back. Best bike investment I ever made. I’m still riding them. And they’ve easily upgraded over the years from standard to disc, to thru-axel. Seriously, I will take these to my grave.

  51. Zons

    Chris King FTW.

  52. miles

    Hi i have a chris king rear hub non disc fun bolt version im wondering how i would go about converting it to disc rather than paying another £400 out for a new hub when this one works fine just would like to use disc now
    Thanks in advance for your time

  53. Shawn

    Does anyone know of a hub that engages it’s pawls in the opposite direction than normal? Or, a hub with pawls that can be reversed?




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