Replacement freehub body for 9-spd Shimano FH-5501 (105)

[Genosse Brymbo]

The Shimano FH-5501 hub on my 9-speed "racing" bike has begun to slip under load and I'm trying to find a replacement.  I can't find any websites offering the 5500/5501 or the 5600 (according to Shimano docs A-compatible) freehub bodies.  Maybe my Google-fu isn't sufficient or there really are none out there.  I'd appreciate if any forumite could suggest a compatible replacement.

[Brucey]

the ev techdoc

http://bike.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FH/EV-FH-5501-2170_v1_m56577569830608912.pdf

shows a freehub body with the 'standard' interface to the hub and rubber lip seal on the RH cone that seals against the dustcap.

This means that -provided you are happy to rework the RH seal arrangements- there are very many freehub bodies that might fit.

For example FH-M570 freehub body http://www.sjscycles.com/Drawings/Shimano/Shimano_Deore_LX_FH-M570_Tech_Doc.pdf

might fit directly, and if it doesn't, you may be able to make it fit by using the dustcap from the old freehub body (which is possible but sometimes tricky) .

But before doing any of that, I would urge you to try lubricating the freehub body first; the pawls may just be sticky.  If you remove the axle, often you can get good enough access to allow oil to be added directly (near where the RH hub bearings go) and this will work its way into the freewheel mechanism in use.  If you remove the freehub body you can add lube to the rear (remove the seal first if there is one) instead.  Something like ATF is a good lubricant for claggy freehub bodies; after a few minutes of spinning the wheel (whilst holding the freehub body) the vast majority of freehub bodies like yours start working OK again.

cheers

[P Walsh]

I removed a freehub body from a 9 speed Ultegra hub and got lube in by removing the O-ring seal from the back (nearest the spokes). That unit was just noisy, as if dry, so it might not work with your problem. But all it would cost you is 10 minutes and a bit of oil.

[Torslanda]

Or get Brucey to overhaul it for you?

[drossall]

The freehub on my Ultegra 6500s was playing up today, freewheeling in both directions, i.e. pawls not engaging. I think I have a spare in the loft but, as I value these wheels, I've just grabbed another on eBay.

However, having stripped and serviced a Regina freewheel way back, my instinct is to see whether it can be saved. I know I can't really take it apart and expect the seals to be OK, but what are current views on trying to get some lubricant in? Waste of time of course if the pawl springs are failing. This is after all high summer (if a bit wet), while this discussion was about the age-old problem of pawls freezing, and the traditional solutions.

It was making occasional nasty clunking noises, which I now realise were a warning. It was mostly OK, but every now and then I'd freewheel down a hill and find I couldn't start pedalling again. In the end I sort of pretended I was on fixed, and tried not to stop pedalling too much. Then I got a puncture and had to stop

[Brucey]

a summertime failure of this sort is usually caused by the same thing as a wintertime failure; water ingress and poor lubrication.

 But instead of freezing, in the summertime the water causes corrosion, the corrosion turns the conditions slightly acidic, and the acid turns the grease thickener, er, 'thicker', and the pawls stop moving freely.

Remarkably a small quantity of the usual (crappy) grease plus a small quantity of water can result in a mechanism that appears to be entirely full of brown stuff that has the approximate consistency of cheddar cheese.

I've dismantled many such failing freehubs and maybe a few in a hundred will have a real show stopping problem such as

- enough corrosion that the pawl spring is no longer going to be reliable
- enough wear in the bearings that there will still be intense rumbling when the bearings are adjusted correctly or free play even if all the shims are removed
- broken pawl spring
- chipped or broken pawls

but IME the rest of them will come back to life if they are simply flushed with oil and then used normally.

There are two pawls in most shimano freehubs, which are designed to engage at the same time; to lose drive entirely both of them need to become jammed.  Occasionally the dog ring will fill up with crud and literally prevent the pawls from extending fully, but more commonly the spring (which is a single turn wire that sits in a groove) starts to bind in its slot so that it isn't pushing the pawls out very well. When this happens the pawls themselves usually don't move freely either.

At speed, the pawls are likely to be (kind of) centrifuged into engagement, even if the spring isn't really helping. Similarly going down a bumpy road can help jiggle the pawls enough to make the thing work sometimes.  This means that picking up the drive (on any one ride) is most likely to fail at low speeds on smooth surfaces.

If the spring is stuck in entirely the wrong place (which can happen) or is broken, or there is enough crud surrounding the pawl,  the heel of a pawl may not be held in the right place either; this can allow the pawl to snatch at the dog ring during freewheeling, which is kind of alarming. 

 The other thing that happens is that whilst the bike isn't being used, nothing is moving and everything is still variously corroding/turning the grease to brown cheese, so you can pull the bike out of the shed and the freewheel can have decided to stop working in the meantime. In extremis the bearings can corrode and start to seize up too.

But if you add oil into the RHS of the hub (as per my earlier post) and there are any signs of life at all, it is worth persevering with it for a while. If the axle is out you can hold the freewheel body and spin the wheel for a few minutes.  To simulate road speeds the wheel must be turning at a fair rate; ~20mph is about 5 revolutions per second, i.e. about 300rpm.  [BTW you could turn the freewheel body at this speed using an electric drill (that reverses) but this is not as good as spinning the wheel because the latter generates centrifugal forces on the pawls and the drill method doesn't.]

After a bit of this "exercising treatment" the usual thing is that the freehub body starts to wee out something unpleasant (that looks a bit like brown sauce, but that you wouldn't want in your bacon sarnie) from every orifice, and the pawls may be starting to work more or less OK.  At this stage you can carry on as you are or fill the hub up with oil and go for a ride. If you do the latter , expect more brown-ness to exude and have to be cleaned up.

 After a bit of this treatment, go back into the hub and use a lubricant that will stay inside better in the long term. You can flush the workings out using GT85 or WD40 at this stage before you add the permanent lubricant.  If the seals are perfect, you can use gear oil, if they are pretty good, you can use a runny SFG (semi fluid grease), and if they are non-existent you maybe need to use an SFG in the freehub body (and hope that enough stays inside to do some good) whilst using a #2 grease in the hub bearings.

BTW it isn't always a good idea to use something like GT85 or WD40 earlier in the process. The reason for this is that whilst it may free off the mechanism more quickly, it can be 'a false dawn' especially if there is a lot of cheese inside. The pawls may start to move OK, but then once the solvent has flashed off, they may become sticky again. The small amount of oil in the GT85 can soak away into the remaining cheese, leaving the pawls bone dry or worse yet coated in even stickier cheese than before. By contrast if you use oil and the pawls free up, they usually stay freed up somewhat more reliably. Something like paraffin (which doesn't evaporate too quickly) isn't a bad idea for flushing, but the mess it makes can be unbelievable, and you need to get all the paraffin out before you put in the permanent lube, because paraffin will degrade the properties of any lubricant, and takes ages (months) to evaporate away once it is mixed with something else.

So in summary, it is always worth a go at flushing the freehub body in situ, but it may not come back to life quickly or indeed it usually turns out that the bearings need adjusting anyway. 

  It is possible to reshim the bearings without taking the whole freehub to pieces but
a) you need the correct tools to do this and
b) you need the freehub body to be in situ to do it and
c) there is no point in re-shimming unless the freehub body has at least been "exercised" thoroughly; the bearing adjustment will most likely change quickly in service otherwise.

If you decide to take the whole thing apart this will obviously give you the opportunity to resolve any cheese issues within, but it is so fiddly that it takes about twice as long as simply re-shimming and flushing does.

BTW if the freehub body has an appreciable amount of free play and is a bit corroded within, you will probably find that the (~50 off) 1/8" balls will be badly corroded. The corrosion/wear in the balls will usually be responsible for about half of the total wear (and about 1/3rd of the rumbling), so replacing the balls will improve matters even if the shims are not adjusted.

hth

[Polar Bear]

I have found Shimano  9 speed freehubs to be totally reliable for two decades now.   Yes, we rarely ride in damp conditions but even so, they have been totally bombproof for us in service.  I bought a spare 9 speed LX freehub about ten years ago as it was cheap in a closing down sale and it remains unused in it's original box in the workshop.   All our hubs are 9 speed Ultegra or XT and we've never suffered any axle or bearing issues either.   Shimano hit the sweet spot with 9 speed imo.

My last solo machine will feature a Hope rear hub and I expect that I will need to service bearings, springs and pawls but at least they are easily accessible.

[drossall]

Thanks both. I think, from what I have read before, I was rather in the mindset that you can't do anything (even lubrication) without ruining the seals. Clearly not.

I'll do as Brucey says, but disassembly is an interesting possibility. As I said, I've done freewheels before (I've got the tool for a Suntour compact 6 freewheel in my box somewhere), so I'd at least know what state the insides were in from actually having seen them. What tools are needed if I have to go that far? And do you need different ones for each Shimano freehub ever made?

[Polar Bear]

I don't know if this link is of any assistance to you.   It's one of those things that I've been considering having a go at for years but the need has never arisen.

[Brucey]

.... What tools are needed if I have to go that far? And do you need different ones for each Shimano freehub ever made?

Tool-wise you need something to get the seal out of the RH end of the freehub body and then a special tool to unscrew the RH hub ballrace, which is on a LH thread.

The correct tool/method for the dustcap will vary with the type and whether you intend to re-use the seal or not.

Shimano used to make a special tool TL-FH20




for this purpose. There are a few other tools of similar type which have been made by others too.  Commonly folk improvise by grinding a socket to fit.

This sort of tool will fit every shimano freehub body. However a few of them have four slots and a reputation for cracking, so if that is the sort you have, making a (well made, accurate) four-prong tool might be the best thing to do.

The two-prong tool also fits most off-brand shimano compatible freehubs too.
Bolting through the centre is a very good idea, else the prongs tend to slip out. I built a special tool which features replaceable dogs and a built-in through-bolt. It also serves as a workstand for the hub, and (usually) prevents the loss of stray 1/8" balls which have an irritating tendency to disappear into the hubshell otherwise...

Inside the workings are much like any freewheel. When disassembling, it is best to pick out the top layer of balls using a magnetic screwdriver. The lower balls are best captured by inverting the whole affair over a bowl of some kind.
If you remove the pawls, it isn't a bad idea to return them to their original positions, since they wear in use and won't share the load so well if they are swapped in position.

When reassembling, the lower set of balls need to be stuck in place (on the inner part of the assy) using some #2 grease. The upper balls can go in loose aftgrewards; provided the base shim is undisturbed, the upper balls can't go anywhere.  However if the base shim is disturbed, there is a chance that one or more upper  balls will drop down into the unoccupied 'third slot' in the body. Leaving a ball in there 'would be a very bad thing' so if in doubt, check.

To simply reshim a freehub, you need to be able to lift shims off the stack without disturbing the base shim or losing any of the balls. I have found that the best way of lifting shims is to use two small jewellers screwdrivers or special paddle tools that are made from flattened spokes. The adjusting shims (unlike the thicker base shim) are slack on the diameter, so can usually be nudged sideways one at a time before they are lifted. Often two come away at once or one comes away with the  ballrace as it is unscrewed, so they can get away from you if you are not careful.

The base shim is often indented where it bears against the slotted body. This can mean that if it is moved to a different position, the apparent bearing adjustment isn't 'true' until the ballrace is fully retightened, and the indentations are squashed flat/remade as necessary. In any event when checking the adjustment the ballrace needs to be well down; 20ftlbs or so, vs a bit more when the adjustment is finished. If you leave the ballrace loose or not down on the shim stack, it will precess in service and this would be 'another bad thing'.

Shims from off-brand freehub bodies look the same but are often different to shimano ones, and (IIRC) won't fit over the centre part of a shimano body. If you try to use shimano shims in an off-brand freehub, they are slack enough on the diameter that they can foul the balls in the upper ballrace if they go off-centre.

Shims go from ~0.05mm upwards. Because they don't always overlap perfectly when stacked, they get little burrs and creases at the edges which makes them difficult to measure accurately; using a micrometer it is usual to have to use a little more force than normal to get a reasonably accurate reading. In practice you can feel how flexible they are and use this as a rough proxy for thickness. When you flex them this is when you find if you have two stuck together or not....

0.05mm shims don't appear in every freehub body and anyway don't give perfect adjustment. A freehub that is 0.1mm wrong on the shim stack is really quite slack and one that is 0.05mm out is noticeably loose. If you rob shims from old freehub bodies you will find that some of the thicker ones are odd measurements so that in theory you can get to with 0.03mm of 'perfect', if you have the right shims. You can of course make shims from beer can etc too but if you use an alu shim it is best to have it in the middle of the stack because it might get torn up if it is left at the top.

To get 'perfect adjustment' it is possible to lap the mating face of the ballrace; it takes a few minutes using 400 grit paper to remove about 5-10 microns (0.005-0.01mm) so it can be tedious work. I often use a special flat grinding wheel for lapping, which is much faster, but somewhat more risky.

If you grind or lap, it is important to clean the part thoroughly before each trial fitting, else you could well get bits of carborundum in the workings.

I've done hundreds of these blessed things by now; often I can do it quite quickly because I know roughly what a modest wobble means in shim terms, and I have lots of spare shims now (a stack about 1" high.... ). So I often pull the top two or three shims out, measure the stack, take the top shim out or build a shorter stack and try it. Occasionally it comes right first time.

Then there are the other times, when it turns out that you need to replace the base shim (because it is too thick) and the shims are all a funny size and you don't have the right ones...  so if it all goes well it might take about twenty minutes (including sorting the hub bearings out) but if it goes the other way then it might be an hour.  If you are doing it for the first time it could easily take two or three times longer, plus any delays to get the required tools and shims together.

It isn't actually very difficult or anything but there are a few possible pitfalls which I have outlined above.

hth

cheers

[drossall]

Wow. That should be published as a manual. Thanks very much indeed.

I've found the various substitutes for the FH-40 on eBay, if I need one. Looks like this freehub is going to get a new lease of life, just as soon as I have a spare evening.

Are parts available too, from the importers at least?

[Brucey]

Are parts available too, from the importers at least?

nope.. {apart from RH seals. There is a rubber one that is used on the cheaper shimano wheelsets, which will do for most other hubs too because it seals on the cone itself provided it has a 17mm diameter somewhere}

... so robbing parts from scrap units is one way to go. But if necessary

- balls are 1/8" ones, and even cheap new weldtite balls are better than rusty  ones
- the pawl spring can be replaced with one made in piano wire
- beer can shims work well (with the earlier caveat about alu ones)
- worn but essentially intact pawls can be reground at the tips. It is important to leave them as long as possible (else they may not engage fully, but you can check this later) and that they are made the exact same length as one another.
- pawls can be substituted with ones from a (scrap) cheap shimano freewheel (which are slightly narrower and not quite as strong) or those from the low gear drive in a current SA NIG three speed hub (which are wide enough but may need to be modified slightly by grinding to size) The latter cost £1 each.
- RH ball cups swap between many shimano freehub models (with the same size axle diameter etc), but not all.
- rumbly freewheel bearing surfaces can be recovered by light grinding, if you can be bothered. To all intents and purposes the parts are 'all hard' and will take a light grind very well. This takes a while and is only worth it for a freehub body that you can't otherwise replace at any cost (which is many of them at the moment since MADison can't be bothered to keep them in stock.... ).

BTW I have mentioned this before but the freewheel bearing is unlike any other bearing on a bike; it sees load when it isn't moving and it sees movement when it isn't under load. It is nice if it isn't, but don't think it really matters a jot if a freewheel bearing is a bit rough.

By contrast if it has free play in it, this is of far more concern; the freewheel won't run true under load and will often squirm about in a potentially power-robbing way.

cheers