Servicing Shimano SLX M665 Freehub

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CREPELLO
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Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

I've already posted about trying to remove the rear seal of an SLX M665 freehub in order to lube it. viewtopic.php?f=5&t=110810

As that isn't possible, I decided to soak the FH in white spirit, then a bath of engine oil. Well I soaked it only to discover something rattle and rolling around the inside of the hub. This isn't a good sign, so I decided to dismantle the hub.

Of the guides on the internet, they don't seem to pick up my next problem (they all relate to the more standard looking Shimano freehub). I made a freehub dismantling tool (badly!), but it did the job of removing the bearing cup. Now I can't make any further progress. Except a shim has fallen out. I also noticed something like swarf in the gap where the pawls are. Odd little pieces they are, about 6mm long, c0.5mm wide, dead straight and very brittle. Tapping the hub on the table got 4-5 of these bits out. Rotating the hub, I can see each of the 4 pawls (it is supposed to be 4, isn't it?) engage in turn. So they appear to be functioning correctly.

Would like to get inside to clean the hub properly. Any ideas how I can proceed? Thanks.
Last edited by CREPELLO on 3 Dec 2016, 12:45pm, edited 1 time in total.
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Gattonero
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Re: Servicing Shimano SLX freehub

Post by Gattonero »

If you have removed the outer race, everything comes off and you are looking to find this:

Image

Clean thoroughly then inspect the pawls seat, and the spring for damage, also the ratchet ring machined inside the freehub body. If all seems ok repack with very light grease (this is Welditite Teflon) and redo the outer race.

Image

You should not have any sensible amount of play, nor any tight spot.

If all fails, don't waste your time flogging a dead horse, new freehubs are not expensive.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

Thanks for that info Gattonero. You say that once the outer race is removed, it should all come apart. This is the problem, it doesn't. I've tapped the rear of the hub on the table several more times. This has dislodged the remaining shims, but the pawl body is still locked in place by something.
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

Should the pawl body come out from the front or rear of the freehub body?

I'm guessing it should come out the rear, but having inserted a screwdriver handle into the front of the hub and whacked the screwdriver tip vertically down onto the table to try and push the pawl body out, it's clear that it doesn't want to move.

Is it that wretched rear seal that I originally wanted to remove for a bit of lube that is stopping the pawl body ejecting? Think it is. Where are my bloody emoticons when I need them???
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

Yes, it was the rear seal, which is reinforced metal and press sealed into the back of the FH. I inserted a big piece of wooden dowel into the front of the hub and keeping my thumb on top of the rear, whacked the hub down harder onto the dowel. The seal broke free. I only managed to drop two ball bearings onto the (clean) shed floor :D

So now I can see inside the thing, everything looks pretty much in order. I don't know what or where the swarf came from. I suspect a steel ball had somehow come adrift and was the rattling thing inside.

I'll take photo's, if they are going to be any help to folks in the future.

Now for reassembly. There's just one odd thing I've noticed. Although the hub appears to be low mileage, it's clear it hadn't been correctly adjusted. The DS cone is lightly pitted. But the DS cup has quite a gouge on the race surface. But it's not clear to me whether this defect is on the bearing track because there isn't the usual faint polished line of the track. I'll take a photo.
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Gattonero
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Re: Servicing Shimano SLX M665 Freehub

Post by Gattonero »

Given that already 3 parts of that hub are not reliable anymore, look around for a new hub of the same kind; for a low price you'll get a new freehub, new axle, new cones, new seals, new ball bearings, new races, new skewer.
If you were to buy freehub+cones+bearings you'll be already over the price of the complete hub. It seems a waste to buy a complete hub, but is not: you'll keep all the spares for the future. Also, you cannot buy the Shimano hub races of that kind, so the get a complete hub is the only solution.
£23 at Rose Bikes
https://www.rosebikes.co.uk/article/shi ... aid:287449
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

A few photos of the stripped down freehub.
DSC_0364.jpg
tmp_1148-DSC_0363695976127.jpg
tmp_1148-DSC_03651213296469.jpg
tmp_1148-DSC_0368-012104182716.jpg

The photo of the bearing cup shows the defect. Looking at it, it almost looks like it might be out of line of the bearing track, which hasn't acquired a polished line yet, such is the little use I reckon the wheels have had.

The inside of the hub wheel shows the teeth are slightly worn in places. This explains the straight shards of brittle metal I found. I'm hoping that now well oiled, the pawls will engage. We'll see. I think the hub must have been subject to a fair bit of loud cracking for that metal to have sheared off.

The pawls are in good condition - four of them held in place by two circlips.

You can also see the metal shards in the picture of the various components. I don't think they caused the rattling sound, more likely a stray ball bearing.

I'll probably end up buying another donor hub sometime soon. I guess I was unlucky. I bought the wheels of eBay. The photos looked promising, but I suspect the wheels are typical of many shimano wheels - not set up or serviced properly. Odd that they are shod with SunCR18 rims and nice black double butted DTSwiss spokes. Suggests wheels of a modest enthusiast of some kind, rather than the usual factory wheels which get neglected. The cone nuts were loose on the front wheel and a bit tight on the rear....
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Gattonero
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Re: Servicing Shimano SLX M665 Freehub

Post by Gattonero »

The pawls and driver body look fine, but the outer race and the teeth inside the freehub shell don't look good to me (for what I can see).

It's up to you, do you always have time to take apart a freehub? Good, you can carry on and it's all learning.
Personally, I'd put all but the driver with pawls in the bin for recycling metal.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
Brucey
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Re: Servicing Shimano SLX M665 Freehub

Post by Brucey »

I would advise a very careful inspection of the pawls; in that model freehub body each one should have two 'ears', (one each side) that the springs bear against. The most common mode of failure with this style of freehub body is that the ears start breaking off the pawls, which then causes the freewheeling action to be poor (the hub intermittently locks up).

The ears break off I suspect because the design is 'very stupid indeed'; if there is the slightest slack in the freewheel bearings, the freehub body skews under any off-centre load and this puts a massive force onto the corner of the pawls which then breaks the ears off. I think that typically, low gear use breaks off the ears on the left side of each pawl. The cure may well be to;

a) grind a relief on the back of the pawls so that the corners near the ears are never loaded and
b) to be sure that there is no free play in the freewheel bearings.

If any pawls are missing ears such that they are no longer held securely, you are better off omitting those from the hub. If you have just two good pawls, in this model of hub install them opposite one another if you can do.

IIRC in this model freehub body there are four pawls in two different patterns, such that one spring works one opposite pair of pawls, and the other spring works the other opposite pair of pawls. Important: in both cases the 'ear' that doesn't see the spring load that works the pawl should still be covered over by the other spring, such that each pawl is retained at both ends.

I think the wear on the adjusting cup is indeed in the bearing track (the contact angle is not 45 degrees in these hubs). Although not perfect, a single pit on both the cone and the adjusting cup may not spell instant doom for the hub; often if the hub is adjusted correctly (a little free play that just disappears as the QR is tightened) such wear may not get any worse for a long time. Given that there are several parts that are less than perfect, I doubt that there is much to risk by using these parts together.

The freehub that Gattonero has shown photos of appears to be from a FH-RM30 or RM40 or similar; the internal layout is different (it has only two pawls, not set opposite one another), no rear body seal, and a different engagement spline to the hubshell. Apart from the last of these things, it is very similar to most shimano freehubs made in the last 30 years or so; for many years few freehub models had seals on the rear of the body.

If you can remove the pawls and show a photo of them, it may be possible to see if they are intact or (as I suspect) they are the source of the shrapnel you have found.

cheers
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

Brucey, I've put the hub back together now, although I've now realised that all the lube (grease on the balls + engine oil for the pawls) has resulted in a lot of drag and consequent dragging of the chain when I back pedal -Doh!.. Which was the reason that motivated me to dismantle the hub in the first place! As I didn't find it a hugely demanding job (once I was past figuring out how to pop the seal off the rear which was holding it all together) I may dismantle the hub AGAIN and thin the lube out if I can. Or buy a new hub. But then can I trust the lubrication of the new hub?

When I was studying the pawls, because each pawl only seemed to have one ear, and they alternated L to R with each pawl, I assumed it was the design and a pretty odd design. I didn't notice enough broken metal inside to make me think that the pawls had broken 4 complete ears. The swarf I found I feel has come from the tips of the FH body teeth.

I'll certainly be servicing the freehubs on my LX wheelsets now I've opened up this one. They have suffered from the occasional "crack" when putting power down.
Brucey
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Re: Servicing Shimano SLX M665 Freehub

Post by Brucey »

One of the ways the freehub can go draggy like that is if too many shims are removed; when this happens the pressure in the main hub bearings passes through the freewheel bearings, and in use the adjusting cup precesses inwards until the freewheel bearings bind completely. #2 grease in the bearings and #2 grease in the seals cause drag that confuses the issue when you are setting up the freewheel bearings.

BTW as I mentioned earlier, if the seals are good, you may as well use oil in the freewheel bearings.

If you want really precise adjustment, you can lap the back of the adjusting race (say 10um at a time) until the free play is gone from the bearing. This means the adjustment is about x5 more accurate than using shims alone; IIRC the thinnest shim (which is not present in every freewheel shim stack) is about 50um.

With a new hub, you can always do better than the factory lube. My advice is to run the hub for a few hundred miles and then overhaul it (including shimming the freewheel bearings, better lube etc). WIth just a little routine maintenance thereafter, hubs so treated ought to have a very long service life.

In fairness I think these pawls are slightly different from those used in other four-pawl freehub assys, like the current XT ones. I think each pawl has one obvious 'ear' for springing and a second, smaller, more abbreviated one for retention purposes. I shall have to pay more attention next time I take one apart.... :wink:

BTW IIRC the LX hubs have a freehub body that has two pawls in, a bit like the RM30 ones. However there is a pastrycutter hub interface like the SLX freewheel body, and a rear seal that is a bit like the deore ones, i.e. it is an all-rubber seal that can be hooked out fairly easily.

cheers
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

I think the bearing adjustment is just about right - I can feel the slightest amount of play when wiggling the cassette side to side. So it must be too much grease. But when assembling the hub, I needed the grease simply as a 'holder' for installing the 50 balls onto the races. I did smear the tiniest amount of grease onto the pawl interface, which looking back, wasn't needed. Where can I reduce the amount of grease used? It's easy if only flushing the hub out and relubing, but not sure how if rebuilding the hub. Perhaps I can just try using less grease (probably..), or spray some semi fluid grease and let dry.
Brucey
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Re: Servicing Shimano SLX M665 Freehub

Post by Brucey »

if you add oil now, it ought to mix with the grease and make a mixture that is less draggy. It might get less draggy by itself after a period of use, too.

If you use a #2 grease on the pawls, it can go underneath them and they can become sticky enough that they won't engage reliably. This is quite a good way of damaging a freehub.

BTW the only place you need grease is to hold the left side freewheel balls; the other set will find their position well enough by themselves, (provided the shim stack is in place). I usually just pick the right side freewheel balls up using a magnetised screwdriver tip and drop them into position.

cheers
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CREPELLO
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Re: Servicing Shimano SLX M665 Freehub

Post by CREPELLO »

Thanks Brucey. I'll be coming back to the hub later and will bookmark this thread for future ref.
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