Shimano dynamo hub bearing service - impossible?

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Brianjeff50
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Shimano dynamo hub bearing service - impossible?

Post by Brianjeff50 »

My front wheel hub bearings have got pretty rickety. Up on the stand I can give the wheel a good old wobble about. I've done a bit to adjust the LH cup and cone but from what I read attempting to get at the RH side is something even a bomb disposal expert wouldn't want to try because the wires are so fragile.
Any advice? Is there any way back if I do break the wires? Any alternative therapies?
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gaz
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Re: Shimano dynamo hub bearing service - impossible?

Post by gaz »

Delicate work, and most likely beyond my own skills but if your hub is that far gone what do you have to lose? viewtopic.php?t=117634

If you can find the same model of hub new, transplanting the innards into your current shell is comparatively straightforward. Otherwise it's a new wheel or rebuild on to a new hub.
High on a cocktail of flossy teacakes and marmalade
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freiston
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Re: Shimano dynamo hub bearing service - impossible?

Post by freiston »

Pre-submission edit: - I've just seen that another reply has pointed to a previous thread with a working link to the pdf document that I have:
https://www.docdroid.net/0CQRiqZ/overha ... pdf#page=3

There was a bike shop called Trinity Bicycles in Irving, Texas that produced some guides. I just tried their website but it no longer exists. An internet search reveals that the shop closed down in February 2012. I have a Shimano Dynamo Hub Overhaul guide in pdf format but it seems that I can't upload it as an attachment to my post. If you DM me with your email address, I can send you a copy, if you want.
Disclaimer: Treat what I say with caution and if possible, wait for someone with more knowledge and experience to contribute. ;)
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interestedcp
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Re: Shimano dynamo hub bearing service - impossible?

Post by interestedcp »

It depends on what model dynamo hub you have. Shimano hubs are among those that can be DIY serviced.

I have some older photos of the process on flickr. Perhaps they can be a helpful addition to the "Trinity guide"

This is the critical step in disassembling a Shimano dynamo hub:
https://www.flickr.com/photos/28712360@ ... 604079324/

If you don't fixate the connector while turning the locknut, the internal wire will break.
There are some text to the picture that may be of some help.

Some advice:
Even with doing the above step correctly, there are still a chance of the wire breaking if you aren't careful. Try to bend the wire as little as possible.

When assembling the internal assembly and screwing on the cone again, it looks like it is going to strip the wire, but it doesn't, so don't try force the wire completely down the slot in the axle, it will just stress the wire.

If it is a 3N80 and the internal assembly doesn't come off easily, don't try to force it off by using a wrench, the hex-shaped "nut" on the cap is rather soft, at you may easily ruin the hub. Buy/borrow/make an appropriate tool like the Shimano tool meant for this, or try penetrating oil or similar, but don't use too much force.

Here is the entire album.
https://www.flickr.com/photos/28712360@ ... 700900333/

There are also some youtube videos, that may be worth watching.
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Cyckelgalen
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Re: Shimano dynamo hub bearing service - impossible?

Post by Cyckelgalen »

If it is only a matter of adjusting, you can always do that on any cup-and-cone hub working on one side only, that is, one cone and locknut, and that will adjust both bearings.
What I would do is taking it apart, the internal assembly comes out as a whole unit and you don't disturb any connector wires. One issue is that many Shimano hubs require a large octagonal spanner to undo the internal assembly.

Taking it apart will allow to do two things:
1- With the internal assembly out and away from the shell magnets, you will be able to feel more precisely how smooth or notchy the bearing on the connector side is.
2- You will be able to fully service and inspect the other bearing and, crucially, the state of this bearing (damaged races/balls) will give you an indication of how the connector side bearing might be.

If they seem reasonably well, just put everything back with one bearing properly clean and lubed and provided it is well adjusted, you'll get plenty of miles out of the hub.
If the races and balls on the bearing that you undo are very damaged, both sides will be most likely equally damaged and, in this case, you have nothing to lose if you attempt to service/repair the bearing in the internal assembly (connector side).

Servicing hubs is straight forward if you just need to clean, lube and replace balls. If you need cones, they can be difficult to source. Same goes for the whole internal assembly, often sold as a spare, if you can find it. Try to identify the parts in your particular hub and see if they are available anywhere. Not easy these days.
LuckyLuke
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Re: Shimano dynamo hub bearing service - impossible?

Post by LuckyLuke »

Hi, I have done this job a 3 times I think, with Shimano Dynamo hubs ending 72, 80 and ?30 I think (a lower spec model with an axle rather than QR).
The bike shop pdf and the advice on here from was invaluable (what a fantastic forum this is!)
I recall the innards of each hub varied slightly from model to model, and the usual best practice of laying out the parts in order, taking pics on the way helped me. It was deffo squeeky bum time the first time I did it!
IIRC there was a post on here (?Brucey or Cyclegalen) mentioning that the delicate wire is more delicate than it used to be, due to changes in materials. (?from copper to alu. But I may have imagined this).
I would suggest going for it, as if your hub is a bit knackered anyway, you haven’t much to lose?
Alternatively, I think Brucey described a partial dismantling, whereby one makes just enough space to squirt grease on the RHS bearings.
Best of luck!
Luke
mattheus
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Re: Shimano dynamo hub bearing service - impossible?

Post by mattheus »

LuckyLuke wrote: 23 Sep 2022, 7:59am Alternatively, I think Brucey described a partial dismantling, whereby one makes just enough space to squirt grease on the RHS bearings.
Best of luck!
Luke
I've done exactly this. (if there is a delicate part that can be broken in a thing, I *will* break it). It helped to use a cheap plastic syringe (which luckily I could acquire from work. But they are cheap!)

Made the hub "like new", but I presume it won't last forever.
jb
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Re: Shimano dynamo hub bearing service - impossible?

Post by jb »

If a cone that was previously okay now needs adjusting its already knackered all that adjusting will achieve is an extremely rough feeling axle, albeit with no play. Okay to do to get a few extra miles out of a work bike but not for anything serious.

Brucey had some success polishing the cones to get them smooth again but this requires a full dismantle of the hub.
Cheers
J Bro
rogerzilla
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Re: Shimano dynamo hub bearing service - impossible?

Post by rogerzilla »

The Brompton one (and the similar hubs nade to fit Moultons and Dahons, with different widths and axle diameters) is fairly easy and there is almost no risk of breaking the wire. If only Shimano made them all like that.
Brianjeff50
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Re: Shimano dynamo hub bearing service - impossible?

Post by Brianjeff50 »

With the help of the Trinity Bikes guide and extensive photos on here I successfully got my Shimano DN71 apart. Indeed it wasn’t as tricky as I feared.

Unfortunately pride comes before a fall and I managed to break the fragile wire on re-assembly. Grr! It’s a much more fiddly job than the disassembly and my recurring problem was that the wire somehow wasn’t long enough to reach the plug end. Anyway in the end it broke.
Re-soldering a new wire is beyond my skill set. I may look out for a replacement set of internals but most appear to be 3N-72: will this fit my 3-N71 case?
Worth a shot though.
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Sum
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Re: Shimano dynamo hub bearing service - impossible?

Post by Sum »

Bad luck!

According to their Shimano tech docs, there isn't much compatibility between the DH-3N71 and DH-3N72, including the internal assembly which is the bit you'll need:-
https://si.shimano.com/en/pdfs/ev/DH-3N ... -2419B.pdf
https://si.shimano.com/en/pdfs/ev/DH-3N ... 2-2847.pdf
I don't know enough about them to say whether it's possible to adapt the parts. I guess you could buy a complete DH-3N71 hub as a parts donor?
Brianjeff50
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Re: Shimano dynamo hub bearing service - impossible?

Post by Brianjeff50 »

Thanks for that. I’m keeping my eyes open for a unit to rob the innards from.
RJC
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Re: Shimano dynamo hub bearing service - impossible?

Post by RJC »

I think the DN-71 had an issue that one of the cones was prone to breaking as it was rather thin. I think this was addressed with the DN-72. Maybe something to consider.
rjb
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Re: Shimano dynamo hub bearing service - impossible?

Post by rjb »

I'm running a Shimano disc dynohub on the tandem a DH3N71. Not experienced any issue with cones breaking. It's done 30,000 miles on the tandem and was second hand when I acquired it. BTW it's possible to repair a broken cable in the hub. The wire is copper not aluminium so easier to solder. Brucey gave some directions but can I find it know. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
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interestedcp
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Re: Shimano dynamo hub bearing service - impossible?

Post by interestedcp »

rjb wrote: 3 Oct 2022, 4:39pm I'm running a Shimano disc dynohub on the tandem a DH3N71. Not experienced any issue with cones breaking. It's done 30,000 miles on the tandem and was second hand when I acquired it. BTW it's possible to repair a broken cable in the hub. The wire is copper not aluminium so easier to solder. Brucey gave some directions but can I find it know. :wink:
The cones are rather thin at certain points on the 3N71* series, but it probably requires wear on the cone before it is stressed enough to break apart. Look below for a picture of my broken 3N71 cone, notice the thin point in the side of the cone on the exact spot where the bearings have worn a tiny groove.
So if they bearings feels rough at some point and the cones shows wear groves, it would strongly advice stop using the hub.
New cones can only be had by cannibalizing existing NOS hubs.

The wire is indeed tinned copper. There are sometimes some confusion about this, because Shimano materials says the hub uses aluminium instead of copper, but that applies is only to the windings on the stator, not the wire to the connector.

Image

(edit: changed into 3N71. The 3N70 use the same cones as the 3N71, but writing 3N7x as I did is wrong because the 3N72 has new and superior cones)
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