Shimano freehub body internals

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TheBomber
Posts: 520
Joined: 16 Feb 2020, 8:18pm

Shimano freehub body internals

Post by TheBomber »

I've been getting some nasty noises and occasional slipping from a freehub body so I opened it up for a look. One of the pawls feels a little 'lazy' even after all traces of grease were cleaned away so maybe the spring has lost of bit of power. The other possibility is wear on the ratchet serrations - could this really be as worn as it looks or was it manufactured this way?:

IMG_1092.JPG

It may not even be simple wear - there was a sliver of rogue metal loose inside the body which could have broken off from one of the serrations. Unfortunately I'd already thrown it out before I noticed the wear so I can't check it for size now. Although shiny where they touch the serrations, the pawls looked fine and without wear.

Whatever the cause I think it's new freehub time.
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

aye, that is jiggered alright.

RIP

(rest in pieces)
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bgnukem
Posts: 694
Joined: 20 Dec 2010, 5:21pm

Re: Shimano freehub body internals

Post by bgnukem »

Badly worn. The sealing of the freehub bodies isn't up to much - after a wet ride the other week took my Deore LX (Model M570) rear hub apart and found water in the hub bearings and little or no grease in the freehub body, plus more water.

Most people don't re-grease the freehub bearings so not surprisingly they don't last long. I push fresh grease through mine from the rear seal when I grease the hub bearings, but it can be required as often as every ride if it's very wet.

Later designs don't have removable rear seals so it's almost impossible to lubricate the bearings. Typical built-in Shimano obsolescence....
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

pushing grease through in that direction is a lot of work and is 'fighting the tide'. Much better to run the entire RHS of the hub in SFG; much better, much easier.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
MikeDee
Posts: 745
Joined: 11 Dec 2014, 8:36pm

Re: Shimano freehub body internals

Post by MikeDee »

I thought you were only supposed to use oil, not grease, in freewheel mechanisms because grease can prevent the pawls from adequately seating in the ratchet?
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

MikeDee wrote:I thought you were only supposed to use oil, not grease, in freewheel mechanisms because grease can prevent the pawls from adequately seating in the ratchet?


That is about right. If you use SFG, not every SFG is runny enough. IME using a #2 grease is often fatal to freehub bodies; if you get away with it, it probably means you didn't manage to get that much inside the workings after all.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
TheBomber
Posts: 520
Joined: 16 Feb 2020, 8:18pm

Re: Shimano freehub body internals

Post by TheBomber »

Thanks for the diagnosis Brucey.

Ordered myself a freehub replacement - a ‘b’ match is all I can get because the original was titanium on an XTR hub and the replacement is an XT so probably going to be steel. Not complaining as the hubs are from around 2007 so all credit to Shimano that they’re not considered obsolete, and I bet a titanium one would have been the wrong side of a £100.

Interesting that it’s the titanium that has worn, not the (presumably) hardened steel pawls. I guess it really is better to be a hammer than a nail.
bgnukem
Posts: 694
Joined: 20 Dec 2010, 5:21pm

Re: Shimano freehub body internals

Post by bgnukem »

Brucey wrote:
MikeDee wrote:I thought you were only supposed to use oil, not grease, in freewheel mechanisms because grease can prevent the pawls from adequately seating in the ratchet?


That is about right. If you use SFG, not every SFG is runny enough. IME using a #2 grease is often fatal to freehub bodies; if you get away with it, it probably means you didn't manage to get that much inside the workings after all.

cheers


I usually shove it through the rear seal aperture until it emerges into the bearing cavity on the other side of the body, so it finds its way through the body alright. Agreed it's likely too thick but I don't fancy using a lighter grease and it finding its way into the axle bearings. I suppose I've just become used to using NLGI No.2 grease in the axle bearings rather than anything thinner. Maybe SFG would work?

I also believed, though can't prove, that the thicker grease is perhaps less likely to be displaced from the freehub bearings by crud or water, but perhaps not based on my recent hub stripdown after a few weekends of wet rides.....
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

TheBomber wrote:...Ordered myself a freehub replacement - a ‘b’ match is all I can get because the original was titanium on an XTR hub and the replacement is an XT so probably going to be steel......

Interesting that it’s the titanium that has worn, not the (presumably) hardened steel pawls. I guess it really is better to be a hammer than a nail.


Ti isn't really strong enough for a freehub body, not where the pawls engage. You end up being 100% reliant on there being more than one pawl engaged at the same time, even if you are not pushing that hard on the pedals. What tends to happen is that freehub bearings wear slightly and then you can sometimes get one pawl engaged and one half engaged, and of course the half-engaged one breaks the top off the tooth on the freehub body. It is not long from then that it is 'game over'.

bgnukem wrote:

I usually shove it through the rear seal aperture until it emerges into the bearing cavity on the other side of the body, so it finds its way through the body alright. Agreed it's likely too thick but I don't fancy using a lighter grease and it finding its way into the axle bearings. I suppose I've just become used to using NLGI No.2 grease in the axle bearings rather than anything thinner. Maybe SFG would work?

I also believed, though can't prove, that the thicker grease is perhaps less likely to be displaced from the freehub bearings by crud or water, but perhaps not based on my recent hub stripdown after a few weekends of wet rides.....


That it pushes out the other side does not mean it has filled up the pawl pockets and surrounded the pawls entirely, not yet. But it might do once you start using the thing. I once simulated what ought to happen with one of these "purging with #2 grease" routines (eg using a freehub buddy or pushing it in from the back) by disassembling a freehub body and packing it with grease. The pawls immediately stopped moving properly such that the freehub became very 'missy' and I reckoned I'd soon break it if I carried on using it like that. I think what puts the tin hat on it is when the pawl has not just to push grease away as a pawl tip engages, but the pawl is so surrounded by grease that there is 'suction' holding it down too. When you wadge #2 grease into a freehub body from one end I don't think you always get any suction effects immediately but in use you might do once the grease is redistributed.

If there is water in the freehub body, pushing grease in from the back is unlikely to displace it entirely if it is not getting inside in sufficient quantity to make the pawls stick (as it should be doing).

The only thing that keeps seal lips wetted with lube is a supply of clean lube behind the seal which is mobile enough to replenish the seal lips should they become dry or get overwhelmed with water/mud. #2 grease works in car wheel bearings because speeds/temperatures are higher and the grease becomes a lot more fluid and gets around the bearing well. The same grease is nothing like mobile enough when used in bicycle applications, so bicycle seals with #2 grease on them run out of lube, are overwhelmed by crud and start to wear double-quick. Remember that when you are pedalling any slack in the freehub bearings will allow the rear body seal to lift and the seal isn't sliding but is just burping from time to time; it might end up acting like a little pump, doing its best to force water into the bearings.

IME what you want under these conditions is some of the lubricant to be coming out, running from where the main hub bearings are, through the freehub bearings and out of the rear body seal, helping to keep crud at bay. This is the principle that keeps SA hubs clean inside too; however the better the seals are, the smaller the quantity of lube that is required to keep the seal lips wetted and the smaller the amount of lube that leaks past them.

If the seals were perfect then I'd suggest you could use gear oil, in the RHS of the hub. [If you have disc brakes then you pretty much have to use #2 grease in the LHS because otherwise the leakage gets on the disc]. The reality is that the seals in a used hub are rarely perfect either so oil might leak out too fast. Pre-SFG, I used to run my MTB rear hub (which had no seal on the LHS of the freehub body) in gear oil but it needed to be topped up (via the port I'd made in the hubshell) before every wet ride, or immediately afterwards and then ridden a few miles more, in order to flush crud out of the freehub body. I learned the hard way that if I didn't do either of these things then it was possible for the LH freehub body bearing to start corroding between rides, even if I'd topped up the hub after the previous wet ride.

[anecdote alert; many years ago when lip seals were new on shimano hubs (back when they still had narrow barrels too) I suggested to a chum that they might be good enough to run gear oil in a front hub over the winter. This suggestion was met with scepticism but my chum decided to try it and see anyway. He reported that about half the oil was lost (from a new hub) over the course of the entire winter, no crud got inside it at all, and that the leaking oil had protected the hubshell from corrosion too. He said "it has never happened to me before, but once I'd wiped the outside, it looked like new, both inside and out". Much as old oil-encrusted SA hubs do, and for similar reasons.]

The correct SFG is

- mobile enough to keep seal lips wetted and replenish the reservoir behind the seals
- runny enough to allow the pawls to operate normally
- not so runny it wees out of the hub too quickly
- good enough to lubricate the hub bearings and
- contains enough good corrosion inhibitors to prevent corrosion inside the hub should any water get inside, or there be condensation.

A typical #2 grease will usually fail to keep the seal lips wetted, the seal lips then wear, and unless the grease is chock-full of corrosion inhibitors (most aren't) then the resulting porridge of muck and grease has no reason not to stay in the hub, and create its own version of corroding merry hell inside.

Land rover SFG is pretty close to the 'correct' SFG and IME it works well in pretty much any shimano freehub which has a seal on the LHS of the freehub body, (that isn't already completely knackered). All you need to do by way of maintenance is to add a bit more in the RH hub bearing occasionally. Once a year is enough for most uses but once every six months might be advisable in the harshest conditions.

One of my mad schemes is to make a very soft seal ring which gets trapped between the HG lockring and the seal ring behind it. If this works then the seal ring can be drilled, and lube can be pushed through that hole having removed the HG lockring/soft seal only. Easy peasy.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Pebble
Posts: 1930
Joined: 7 Jun 2020, 11:59pm

Re: Shimano freehub body internals

Post by Pebble »

Before I made a tool to disassemble them, if they began to skip in the cold winter weather I used to boil them in thick oil, it used to cure them, my guess was it removed the water which may have been freezing up.


Here is one that failed and jammed, the pawls and the ratchet were good but as you can see it the internal bit that broke.
Image
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

'proper job' ! :shock: :shock:

:lol:

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Pebble
Posts: 1930
Joined: 7 Jun 2020, 11:59pm

Re: Shimano freehub body internals

Post by Pebble »

Brucey wrote:'proper job' ! :shock: :shock:

:lol:

cheers

it had been skipping a bit that day, and I think it was a skip at full power on a 1 in 4 hill that done it - I couldn't freewheel down the other side, and my 20 mile home with it jammed was a bit interesting, it is difficult to remember to keep the legs spinning.
nsew
Posts: 1006
Joined: 14 Dec 2017, 12:38pm

Re: Shimano freehub body internals

Post by nsew »

Freehub grease is available at a cost but goes a long long way https://www.dumondetech.com/portfolio/p ... ub-grease/ or https://www.wychbearings.co.uk/Special_ ... e_50g.html There’s no way you should be re-greasing the internals at daily intervals, worse case scenario would be monthly. There are freehub oils available but professional consensus now favours the grease as it sticks around longer and repels water better. Both the Dumond and Shimano greases flow to minus 30deg so obviously won’t gunk in UK temps. I approve of removing the freehub and rear seal and flowing the freehub grease through from the rear. I apply a little heat to aid the flow while spinning the mechanism. To my mind there’s all kinds of wrong with Brucey’s method and view it as a typical bike shop hack. Personally, I’d purchase a freehub https://www.ebay.co.uk/itm/Shimano-FH-M ... 890.l49292 or whole assembly https://www.ebay.co.uk/itm/Shimano-9-Sp ... 890.l49292 (you may have difficulty removing the freehub without damaging the shell) which would provide a whole bunch of spares. Then you can keep a spare freehub meticulously cleaned and greased, ready to install at whatever intervals you choose. Like you I also use a thick lithium web grease (Rock n Roll Super Web Grease) for the hub bearings and have no problems with migration.

bgnukem wrote:
Brucey wrote:
MikeDee wrote:I thought you were only supposed to use oil, not grease, in freewheel mechanisms because grease can prevent the pawls from adequately seating in the ratchet?


That is about right. If you use SFG, not every SFG is runny enough. IME using a #2 grease is often fatal to freehub bodies; if you get away with it, it probably means you didn't manage to get that much inside the workings after all.

cheers


I usually shove it through the rear seal aperture until it emerges into the bearing cavity on the other side of the body, so it finds its way through the body alright. Agreed it's likely too thick but I don't fancy using a lighter grease and it finding its way into the axle bearings. I suppose I've just become used to using NLGI No.2 grease in the axle bearings rather than anything thinner. Maybe SFG would work?

I also believed, though can't prove, that the thicker grease is perhaps less likely to be displaced from the freehub bearings by crud or water, but perhaps not based on my recent hub stripdown after a few weekends of wet rides.....
bgnukem
Posts: 694
Joined: 20 Dec 2010, 5:21pm

Re: Shimano freehub body internals

Post by bgnukem »

Brucey wrote:
bgnukem wrote:

I usually shove it through the rear seal aperture until it emerges into the bearing cavity on the other side of the body etc...........


That it pushes out the other side does not mean it has filled up the pawl pockets and surrounded the pawls entirely, not yet. But it might do once you start using the thing. I once simulated what ought to happen with one of these "purging with #2 grease" routines (eg using a freehub buddy or pushing it in from the back) by disassembling a freehub body and packing it with grease. The pawls immediately stopped moving properly such that the freehub became very 'missy' and I reckoned I'd soon break it if I carried on using it like that. I think what puts the tin hat on it is when the pawl has not just to push grease away as a pawl tip engages, but the pawl is so surrounded by grease that there is 'suction' holding it down too. When you wadge #2 grease into a freehub body from one end I don't think you always get any suction effects immediately but in use you might do once the grease is redistributed.

If there is water in the freehub body, pushing grease in from the back is unlikely to displace it entirely if it is not getting inside in sufficient quantity to make the pawls stick (as it should be doing).

The only thing that keeps seal lips wetted with lube is a supply of clean lube behind the seal which is mobile enough to replenish the seal lips should they become dry or get overwhelmed with water/mud. #2 grease works in car wheel bearings because speeds/temperatures are higher and the grease becomes a lot more fluid and gets around the bearing well. The same grease is nothing like mobile enough when used in bicycle applications, so bicycle seals with #2 grease on them run out of lube, are overwhelmed by crud and start to wear double-quick. Remember that when you are pedalling any slack in the freehub bearings will allow the rear body seal to lift and the seal isn't sliding but is just burping from time to time; it might end up acting like a little pump, doing its best to force water into the bearings.

IME what you want under these conditions is some of the lubricant to be coming out, running from where the main hub bearings are, through the freehub bearings and out of the rear body seal, helping to keep crud at bay. This is the principle that keeps SA hubs clean inside too; however the better the seals are, the smaller the quantity of lube that is required to keep the seal lips wetted and the smaller the amount of lube that leaks past them.

If the seals were perfect then I'd suggest you could use gear oil, in the RHS of the hub. [If you have disc brakes then you pretty much have to use #2 grease in the LHS because otherwise the leakage gets on the disc]. The reality is that the seals in a used hub are rarely perfect either so oil might leak out too fast. Pre-SFG, I used to run my MTB rear hub (which had no seal on the LHS of the freehub body) in gear oil but it needed to be topped up (via the port I'd made in the hubshell) before every wet ride, or immediately afterwards and then ridden a few miles more, in order to flush crud out of the freehub body. I learned the hard way that if I didn't do either of these things then it was possible for the LH freehub body bearing to start corroding between rides, even if I'd topped up the hub after the previous wet ride.
......
The correct SFG is

- mobile enough to keep seal lips wetted and replenish the reservoir behind the seals
- runny enough to allow the pawls to operate normally
- not so runny it wees out of the hub too quickly
- good enough to lubricate the hub bearings and
- contains enough good corrosion inhibitors to prevent corrosion inside the hub should any water get inside, or there be condensation.

A typical #2 grease will usually fail to keep the seal lips wetted, the seal lips then wear, and unless the grease is chock-full of corrosion inhibitors (most aren't) then the resulting porridge of muck and grease has no reason not to stay in the hub, and create its own version of corroding merry hell inside.

Land rover SFG is pretty close to the 'correct' SFG and IME it works well in pretty much any shimano freehub which has a seal on the LHS of the freehub body, (that isn't already completely knackered). All you need to do by way of maintenance is to add a bit more in the RH hub bearing occasionally. Once a year is enough for most uses but once every six months might be advisable in the harshest conditions.

One of my mad schemes is to make a very soft seal ring which gets trapped between the HG lockring and the seal ring behind it. If this works then the seal ring can be drilled, and lube can be pushed through that hole having removed the HG lockring/soft seal only. Easy peasy.

cheers


With it getting harder to find decent quality 7/8/9-speed freehub bodies I guess some more effort is require preserving the ones I have.

Maybe will try to obtain some LR SFG and experiment. Always thought such grease would be too thin to properly lubricate the hub bearings but I don't know that for a fact.

Having packed the freehub bearings with grease I find some oozes out of the rear seal to form a 'ring' of grease between the seal and the hub shell. My concern with SFG would be that similar seepage might find its way along the spokes and reach the rim, then play havoc with the brakes. I've seen excess No. 2 grease do this before if some has made its way out of the front hub and onto the spokes.

If the freehub rear seal is already worn due to bearing play and/or insufficient lubrication, perhaps it might be too leaky for use with SFG? I've got a freehub dismantling tool but not worked up the courage to use it yet!

Used to have Campag 8-Speed on one bike and there was a hole in the freehub body splined area where fresh grease/oil could be injected once the cassette was removed. Far easier than removing the body! The hubs also had grease ports so it was easy to purge the bearings after a wet or dirty ride. Suntour/WTB Greaseguard hubs were similar. Wish such things were still available!
Brucey
Posts: 44454
Joined: 4 Jan 2012, 6:25pm

Re: Shimano freehub body internals

Post by Brucey »

nsew wrote: ….To my mind there’s all kinds of wrong with Brucey’s method and view it as a typical bike shop hack....


well bike shops won't even spend that long on them (*) and there is absolutely nothing wrong with it as a scheme; I have kept numerous freehubs working quite happily this way and resurrected plenty of others. Maybe folk should actually try it before condemning it....? Wadging grease in from the back is basically a not a very good idea, pretty much a waste of time for the reasons I have already described. Takes much longer to do, works less well; what could be any clearer?

(*) FYI the typical Bike shop routine is

1) new freehub body
2) if no new freehub body available, new hub or new wheel.

If there is the slightest other thing wrong with the hub or the wheel, that tips them into 2) far sooner than you might expect.

IME if SFG starts to come out of a hub (eg because there is too much inside) then you may have to wipe up a couple of times, but that is about as bad as it is likely to get.

If you want to spend the least time in future maintaining freehubs then adjusting them correctly is an excellent idea; they will leak less lube outwards and less water inwards, too. IME if you adjust a used freehub body once that should be it for at least 10K miles; if it goes out before then it is odds-on that water got inside it eg because it wasn't lubed properly.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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