Freehub help

[hatler]

All,

How do I get this freehub off ?  I was expecting a 10mm internal hex bolt as exists in every other freehub I've ever removed, except this one.

[zigzag]

some freehubs need 11mm allen key (formula is one of them iirc)

[hatler]

Bugger, and guess which size Allen key I don't have.

For the life of me I can't see the flats by peering down the hole.

I do know that a 12mm key is too big.

Still, look on the bright side, it's a tool-purchase excuse.

Things could be worse.

Thank you. I'll report back later.

[Brucey]

you may find that you need to use a tool from the LHS to remove the freehub. In this case the fastener can be a captive nut or a captive bolt and the threading can be LH or RH. Or the whole thing can screw into the freehub body on a coarse RH thread; there are many variations.

Especially in smaller wheels, it can prove to be virtually impossible to get enough torque to unscrew the freehub body/ fastener.   I guess you want to remove it so that you can replace it?  In which case you may not know what pattern it is, even, let alone sourced a replacement?

If so, you may find it (net) easier to repair the extant freehub body in situ; they can be rebuilt/reshimmed etc in situ, which completely sidesteps the issue of freehub body removal per se, even if it does raise other issues.

NB in many cases the net result of a repair/reshim is superior to a new freehub body, because new freehub bodies have (or soon develop) free play in the bearings, whereas reshimmed ones are as good as you can be bothered to make them.

 It has been my observation that once the bearing surfaces are 'run in' then provided lubrication is attended to, reshimmed freehub bodies can last practically indefinitely. By contrast even if a new freehub has no free play, it soon develops some in most cases.

cheers

[Jurek]

I see you have a Feedback workstand.
Nice  .

[hatler]

I see you have a Feedback workstand.
Nice  .

Good grief !

'Hawkeye Jurek' to the fore.

[hatler]

Brucey,

Thanks as ever for your knowledge.

What on earth sort of tool does one use to get to the captive nut ?  The whole tube appears to be bereft of anything which one could get any kind of purchase on.

No-one locally has an 11mm Allen key, so I've ordered one online for delivery Sunday.

The purpose of the exercise is because there is a rumble from the freehub bearings on the overrun, the wheel bearings themselves are fine. Slightly disturbingly a couple of bits of swarf dropped out, so I think I do need to get this one off to assess what kind of state it's in.

[S2L]

Screwed on freehubs are the work of the devil...

[hatler]

Oooo, cheer me up some more why don't you.   

[hatler]

Hmmm. Poking round in there it feels like there might be a 12 spline fitting of some sort.

(And I just know this will be a silly question.) Is there such a thing as a standard spline for this sort of application ?  Does this info help pin it down at all ?

[Brucey]

unfortunately it is only by poking something like an 11mm down the hole that you can find out if an 11mm allen key will fit or not.

FWIW the most common origin for swarf in that area is if the dust shield (that is pressed in the end of the freehub body) works loose and starts to chafe against the  RH bearing cup.  If this dust shield moves easily then this is almost certainly the fault. Removing the dust shiled usually shows it to be visibly worn where it has contacted the bearing cup.

Rumbly freehub bearings in this style of freehub are -in isolation-  nothing to be worried about. The reason for this is that the freewheel bearings are either turning whilst under almost zero load,  or loaded and not moving (provided there is no free play in the bearings). However if they have gone rumbly this almost invariably results from water ingress and corrosion, and other troubles (such as free play and/or dicky pawls) are never far away.

So if you lube the freewheel bearings  (with oil or SFG) and the freewheel still works OK, then you can leave it for a whole longer if you want. However if the freehub body is slack on the bearings and/or pukes oil out that is rust coloured, then you can be sure that all is not well within.

cheers

[hatler]

What a fantastic resource you are Brucey !  Many thanks. I'm going to run oil in there now.

[Brucey]

BTW if the dust shield is no longer a tight fit in the freehub body, but isn't yet so worn that it can't be reused, you can usually 're-flare' the dust shield by using the radiused end of a suitable 1/2" drive socket and a little work with a soft hammer.

If the dust shield is borked and is the only thing stopping you from using the hub, shimano make a part that is a good lip seal onto cones which are 17.0mm diameter. This part will fit a lot of off-brand shimano freehub bodies too. IIRC it is the part usually found in FH-M525A.

cheers

[hatler]

Filled with oil. No sign of nasty rusty gunk coming back out. The dust seal is fine.

It's slightly quieter but still as rough as guts. It breaks my engineer's heart to run it like this, and I completely get that it's not going to result in a catastrophic failure.

[Brucey]

if it is truly heartbreaking and you are prepared to accept the possibility that you may not succeed, you can try and rebuild the freehub body. New balls are easy but you can dress or even regrind the bearing surfaces.

  The RH ball cup is left threaded onto the rest of the body and sits on a bed of shims. You need a special tool to undo the cup without breaking it; they vary in tightness and even with the best tool there is a chance that the cup will break before it comes free, if it is super-tight.  With a substandard tool the risks of breakage increase dramatically.

I've dismantled hundreds of these things and to date I have broken two; one was a crap one anyway and I wasn't bothered. The other was a Dura-Ace one and I was. Neither would have been any good at all as they were, because they were so loose, so may be I lost nothing.

Once the thing is apart the components can be spun up in a lathe and polished with wet and dry or even reground.   In each bearing there are three components; the 'cone',  the balls, and the 'cup'. Roughly their importance is in that order as well, so far as smooth running goes, i.e. the cup is usually the least important.

However you will only get 'perfect running' if all three parts are perfectly smooth, and the shimming is perfect too.  The thinnest shim is 0.05mm and this isn't found in every freehub body. If you want the adjustment to be 'perfect' then it is usually necessary to find thicker shims which differ in thickness by 0.01mm or (better yet) you can lap the back of the cup to tolerances of 0.005mm. This approach takes a fair amount of luck and/or patience to get it exactly correct but maybe it is 'worth it' if you like things to be just so.

cheers

[hatler]

Huzzah !!   11mm it is.

Next question. (And again, I think I know this will be silly.)  If this freehub is shot, do hubs have a standard fitting, in other words, would a Shimano freehub fit ?

[S2L]

Huzzah !!   11mm it is.

Next question. (And again, I think I know this will be silly.)  If this freehub is shot, do hubs have a standard fitting, in other words, would a Shimano freehub fit ?

No, you need the correct unit

[zigzag]

even shimano freehubs have several different interfaces. it's sometimes easier to find the whole rear hub and take off the freehub, than source a freehub alone.

[hatler]

Dang, I rather thought this might be the case.

Many thanks again.

[Brucey]

I find sourcing the correct freehub body one of the most frustrating things possible; a pointless forage amongst vendors who misidentify what they have even when they actually have it in stock when they say they do. When the facking thing turns up often as not it has almost as much free play in it as the old one did anyway so you still need to rebuild a freehub, its just one with slightly smoother bearing surfaces.

After going through this exasperating loop a few times I decided that even if it took me a couple of hours I would almost invariably  be better off rebuilding the old freehub body. And it doesn't take me that long.

FWIW given a choice between riding on a play-free freehub with noisy bearings and a freehub body with some free play and quieter bearings, I'd choose the former every time.

 If there is some free play it is only ever going to get worse, and since there is 'movement under load' in such a freehub it is actually costing you effort to ride on this crap too.

If all a freehub body needs is a reshim, then in half an hour or so I can make it better than any similar freehub you can buy. It took me longer than that the first few times of course.

cheers

[hatler]

Freehub off and seal removed revealed it was almost dry. A good clean out and re-lube with some diff oil and all back on the bike, it's about a quarter as annoying as it was previously, and that's good enough for me.

Again, than you all for your detailed help.

(And I have a new tool !!)

[Brucey]

FWIW you don't need to remove the freehub to oil it properly; that you didn't manage it previously just means the oil didn't get all the way in there for some reason.  It sometimes takes a minute or two (of spinning the wheel whilst holding the freehub body) for oil to work its way into the mechanism. You know that it has because
a) the pawls start to sound different and
b) oil starts coming out past the seal at the back of the freehub body

Good lubrication in the long term is best achieved with SFG.

cheers