Dismantling & Lengthening a Shimano XT730 rear hub.

[CREPELLO]

Afternoon all. Last year I bought some nice shiny NOS XT730 hubs and have nearly completed building them into some nice retro touring wheels. This may seem a silly question, but is there a special method of dismantling these hubs? I ask because I can't release the lock nuts, which have a very strange sliding mechanism that I've not come across before. Nor can I find any mention of this issue on the internet...so it's probably just me then In the closed position, the lock nut just spins around. Only when the nut is pulled out does it apparently lock or offer resistance.

Should I just try applying some extra welly to release them? Because I've already applied the standard welly (to assist, I used a standard spanner on the lock nut, due to extra length for leverage, rather than the cone nut spanner). The damn thing feels absolutely solid and I'm afraid of deforming the cone nut flats, which I've already done a bit (probably due to using a 15mm cone spanner on the cone nut - it's 14mm, doh!).

Is it just a case of finding more leverage? If so, how (such narrow flats and the lock nut has a shoulder, which means it's not easy to fit in a vice). Perhaps they've just seized with age, although they seem reassuringly oily on the outside and smooth to turn.

Apart from wanting to be able to open these hubs for servicing, I'd like to extend the rear from 126 to 130 (I'm not going to 135mm, because I don't want to spring my old CB Dalesman frame again and I'm not going to use the bike for touring). I understand that many 9 speed freehubs can be mounted to these older XT hubs and I've got a donor XT760 freehub that I'm hoping to use. Is there anything I should consider when attempting this modification?

These hubs are solid axle versions and I'm hoping that the axle is just long enough with cast steel dropouts. I don't think I'm going to lose any threads at the end of the nuts. Is this the experience of anyone else?

[hamster]

I'm completely puzzled by your post. XT M730 are completely normal in their design - locknut and cone nut on each side. Undo the locknut on the left, remove the spacers (which simply drop onto the axle), undo the cone and withdraw the axle from the right.
Replacement Cyclo hollow axles are £5, so I would use one of those to get a stronger axle and at the right length.

The only problem you may find with a later 9 speed freehub body is that the dust shield annd cone diameters are different to M730 so you will need some donor parts off the 9 speed hub.

[CREPELLO]

A couple of pics showing the sliding lock nut in open and closed position.

Open position means the but will not turn, unless it's supposed to undo. Closed position, the nut just spins around.

What could be the purpose of this assembly?

[rjb]

http://si.shimano.com/pdfs/ev/EV-FH-M730-0789C.pdf
This may help you. Looks like its a normal cup and cone arrangement but with a sleeve locknut and spacer. It looks as if the spacer is stuck inside the locknut but its not obvious from your photo how you access it. Are these the hubs with the rotatable bearing cover which allows you to uncover a greasing hole? Bit more investigation needed, or wait for someone more knowledgeable. Sorry.

[Brucey]

if you blow up the illustration in the ev techdoc (eg ctrl+), all is clear. The QR and nutted versions are different. The nutted version's locknuts comprise a central portion, which is threaded and has a hexagon on one end, and an outer portion, which has a hexagon internally and flat on the outside. The outer part will drive the inner part if it is slid outwards slightly.

This arrangement makes it trickier than normal to get enough purchase to undo the locknuts. [I suggest that you insert a small open ended spanner into the gap so that the outer part cannot slide back to where it came from]. It was such a successful arrangement that I don't think it was used on other shimano hubs....

cheers

[CREPELLO]

(posted before I saw Brucey 's reply)

Thanks fit the link Rjb.it does show that the assembly for the solid axle is different to that of the quick release version. And yes, this is the type of hub with the rotating grease ports.

It does seem that it is still a simple lock nut arrangement. It's just this sliding nut that has thrown me a bit. But I'm still nervous of messing up the nuts or the cone spanners, considering the amount of pressure I've applied so far. How much torque can a cone spanner really take?

Hi Brucey. Yes, I've tried a small adjustable spanner on the sliding lock nut. I'll try a regular spanner next. I just wish I could avoid using a cone spanner on the cone nut.

Also, I'll try a but of Plus Gas, although how such an oily looking nut would have seized, I don't know. The hubs came new in box.

[Brucey]

NB if you need to buy a new axle, it should be one that is M10 x 1 threaded. A 9.5mm or 3/8" one will not do.

I recommend that you get a good quality one, e.g. a shimano one or a CrMo one, not a load of cheap rubbish.

NB you could convert the hubs to QR operation if you wanted to; the axle threading in shimano nutted hubs is the same as in QR versions.

cheers

[CREPELLO]

I'm not sure I really need a new axle. The length of the nutted axle seems long enough that barely any thread is lost due to the shortness - I estimate no more than two threads altogether, which considering the thickness of the chromed nuts...I don't know how many threads they have (10?) but losing one thread per nut isn't going to cause threads to strip.

Also, I understand that a QR axle is stronger, but will a bent solid axle be such a high risk factor? I won't be using the bike for loaded touring duties and I have been a light rider, so gentle on the wheels (I've never broken a spoke). Alas, I've put on some weight but I think I still ride in a mechanically forgiving way and hope to lose the weight - I hope! We'll see.

Have still yet to crack those nuts. Watch this space.

[CREPELLO]

I finally managed to release the able nuts. They were never going to budge whilst mounted on the wheel and the risk of skinning my knuckles wrestling with spanners slipping off the narrow flats of the nuts was too great.

I did find that I could release the lock nut on the nds,then I was able to remove the nds cone and extract the axle.

I couldn't find a way to clamp the axle in the vice, but I could clamp a spanner in the vice, pull on the axle (to lock the lock nut), then bear down on the cone spanner. I'd previously applied a little Plus Gas which may have helped. And bingo!

I'm a bit surprised to see that the cones weren't polished as per usual with high end Shimano hubs . Could someone have swapped the XT cones out for cheaper cones? Would have thought it would be tricky getting the parts to fit. [Edit: having wiped the grease of the cone, it does look very smooth, just that it's black, like the low end hubs ]

I need to establish whether I might be able to lift out the grease port disc and insert it in the new free hub.

Scrap that idea. I think I can still benifit from one grease port on the NDS .The hub has an internal sleeve from what I can see. So I can still inject grease from the NDS to purge the hub, the old grease will exit on the DS.

Incidentally, these hubs don't have neoprene seals, so the grease ports would have been essential.

[CREPELLO]

I'd still like to hear if anyone has any idea/theory as to why the solid axle XT hubs were fitted with sliding two piece lock nuts?

[rjb]

Glad you got it apart. Any chance of a photo which shows the arrangement of the locknut and sleeve. Ive a nagging suspicion I encountered one a long time ago but need to refresh my memory. I certainly recall having a Shimano axle with extremely tight cones and locknut which like you I had to resort to clamping it in a bench vice to get it undone.

[CREPELLO]

OK, so here's a photo of the drive side parts. The two parts of the sleeve nut are in the foreground, left and centre. The smaller nut with thread for the axle simply slots into the larger sleeve.

[Brucey]

IIRC when that XT hub was current, there was no XTR; XT was the top of the heap. Later, Dura-Ace and XTR shared some hub components, and one of the components they shared was (I think) the cup insert in the left side of the rear hub. This was a 'machined from solid' part rather than a 'pressed from sheet metal' part as found on other shimano hubs. It was also a different diameter where it fitted into the hubshell. This being the case, it is quite possible that FH-M730 rear hubs used Dura-Ace sized cup inserts and therefore dustcaps too, potentially making substitution of the LH dustcap with something else a bit tricky.

BTW the RH cone and locknut are not meant to be disturbed; they are meant to be kept very tight. When you have reset them for the new OLN, either make them as tight as they were when you took them apart, and/or use threadlocking compound on them.

I hypothesise that the weird locknut arrangement was so that you only needed to carry one cone spanner; with sliding covers, an ordinary spanner (which would also fit pedals, track nuts etc) would do for the other fitting.

cheers

[CREPELLO]

IIRC when that XT hub was current, there was no XTR; XT was the top of the heap. Later, Dura-Ace and XTR shared some hub components, and one of the components they shared was (I think) the cup insert in the left side of the rear hub. This was a 'machined from solid' part rather than a 'pressed from sheet metal' part as found on other shimano hubs. It was also a different diameter where it fitted into the hubshell. This being the case, it is quite possible that FH-M730 rear hubs used Dura-Ace sized cup inserts and therefore dustcaps too, potentially making substitution of the LH dustcap with something else a bit tricky.

Interesting, but I think it's the RH cone/locknut assy I'll have to replace, due to the grease-port dust cap not fitting the modern freehub. I'm just hoping I've got something suitable in my store to match the XT 760FH

BTW the RH cone and locknut are not meant to be disturbed; they are meant to be kept very tight. When you have reset them for the new OLN, either make them as tight as they were when you took them apart, and/or use threadlocking compound on them.

Indeed. I found that the DS lock nut came undone very easily, so I will be doubling down on that when I come to reassemble.

I hypothesise that the weird locknut arrangement was so that you only needed to carry one cone spanner; with sliding covers, an ordinary spanner (which would also fit pedals, track nuts etc) would do for the other fitting.

cheers

That's the best....and only theory offered so far, so I'll go with that!

[CREPELLO]

I thought I'd update this post as I've been working on the wheel over the weekend.

I mounted an old xt760 freehub that I'd had knocking around for a long time. I sprayed a little of shimano spray chain lube through the seal on the back of the hub then slathered some lithium grease onto the bearings before popping back the seal.

Then to my dismay as I rotated the hub in my hand it was ticking exactly like the sound of the pawls going over the ratchet.

As I had made a freehub dismantling tool a while back I felt I'd nothing to lose but to dissemble the hub as I suspected something had broken loose. Well I got a far as removing the bearing cup when I observed the tiny ball bearings freely moving around on the race, in a rather noisy fashion! Then it clicked - the spray lube had cleaned up the balls and allowed them to move far more freely than normal. So I covered up the balls with some lithium grease and reassembled the hub.

I should have just used engine oil and that's what was in the hub after I lubed it many years ago before storage. I suspected that it has died up which was why I thought a quick squirt of spray lube would rehydrate (so to speak) the old engine oil.

So now to mount the freehub onto the main hub. For donor parts I was hoping an lx t670 would provide everything I needed. I knew I needed a new drive side cone nut. I then realised I'd have to pop the dust seal off the donor hub because the cone seal was incompatible with the xt760 dust seal I was going to use.

I also realised that those funny sliding lock nuts off the original hub wouldn't work, particularly on the NDS where the nut actually functions as a spacer as well, which of course with the hub now respaced,would not created the correct OLN dimension.

I hadn't given this much thought if only because the worst that could happen is the need to purchase another NDS spacer. However, and don't ask me how, I offered up the 10mm spacer from the 135mm lx hub and it produced a convincing 130mm OLN. How that works I'm not sure. The xt732 hub shell is more or less the same width as the lx670 shell. The NDS cone nut and original dust seal are lower profile than that of the lx hub, so there's more space for a spacer. On the DS that sliding lock nut was too wide a profile and was replaced by the thin lock nut off the lx, so everything added up perfectly in the end.

All that was then required was to true up the half finished wheel. The H Plus Son TB14 rims builds up really well - it was easy to get a really round wheel and they look lovely paired with the high polished xt hubs and gum walled Pasela tyres. Oh, and the old 126mm axle was ample for the respaced 130 hub. I think a QR version would also be wide enough for 130 OLN too.

I hope that all makes sense to anyone reading this wishing to undertake a similar respacing to an old shimano hub.

I think that's quite a convincing mod and made up from three different generations of shimano hub