Servicing a Shimano hub dynamo

[Andy in Germany]

I've noticed a very slight wobble on the front wheel of my touring bike, which appears to be due to the bearings on the Dynamo. Has anyone ever tried to deal with such a problem, and where would you start?

I have been looking for tips online but videos seem to focus on servicing the dynamo itself: I suspect the bearing cups are a bit worn and/or loose so I'd like to open it, re-grease the bearings and put it together again. Has anyone tried this, and how would you open them while not demolishing all of the electrical bits?

 

[si_c]

From my understanding it should be cup and cone bearings so you'll likely be able to adjust them yourself to remove the play same as with any other Shimano hub.

 

[rualexander]

I believe the non-connector side can just be opened and treated like any normal cup and cone hub, but the connector side has very delicate wiring which makes opening it up without damaging it quite tricky, but it is possible.
I have seen the procedure detailed somewhere but can't remember where.

 

[si_c]

I believe the non-connector side can just be opened and treated like any normal cup and cone hub, but the connector side has very delicate wiring which makes opening it up without damaging it quite tricky, but it is possible.
I have seen the procedure detailed somewhere but can't remember where.

That makes sense - the non-connector side should be like the adjustable cone on a regular hub - I'd be tempted to loosen that off, pack some grease in and then properly tighten up see if that fixes the wobble.

 

[rualexander]

Some info here https://forum.cyclinguk.org/viewtopic.php?t=117634
Also from that link, this https://www.docdroid.net/0CQRiqZ/overhauling-shimano-dynamo-hubs-dh-3n72.pdf

On youtube

View: https://youtu.be/oXptXRqxj9c


Different model number hubs may differ.

 

[Heltor Chasca]

That link to CTC, up thread was by me once upon a time when I was on that forum and Brucey was/is the mechanical guru. It is possible to loosen the overly tight bearings (from what I understand from his advice) when the hub is new. BUT I don’t know what they are like to service once they have done mileage. Are you a member on the CTC forum? If you don’t get an answer here, maybe sign up there.

My hub still rumbles as I didn’t loosen it in time. However it has been deemed acceptable as it rolls well and provides electricity no problem. In fact the rumbling can only be heard when on a work stand on a wooden floor so it’s not much of an issue.

 

[andrew_s]

Brucey's normal recommendation is to service and adjust the hub when new.

As above, fiddling with the connector side risks breaking the wires, so it's suggested that whilst the left side is loose, the axle be pushed over enough to (hopefully) expose a gap through the connector side seals through which extra grease can be injected via a thin & squashy tube.
The other side greases and adjusts as normal.
Take care not to knock any balls out from the normal position over the edge of the cup.
Correct adjustment is when there's a slight amount of play, which just disappears when the QR is fully tightened.

From previous comment from someone who did so, if you do service the connector side as per the Trinity Cycles document above, after about 3 goes the wire has work hardened enough that you'll almost certainly break it whilst unthreading it the next time.

 

[Andy in Germany]

This hub is probably ancient: it's from another bike that was being scrapped when I worked in a bike shop: I salvaged it and built it into my old Xtracycle wheel. When the rims on that finally gave up, I scrapped the rim and replaced the whole wheel, but kept the hub, and Elder Son then built it onto new rims last year.

This means that the "What to do when new" advice was probably about ten years too late when I first got it, and I've used it for nearly a decade, however when I get the chance I'll try to grease the poor thing...

 

[andrew_s]

This means that the "What to do when new" advice was probably about ten years too late when I first got it

In which case the state of the cups, cones, and balls are as they are.
I'd just squidge as much extra grease in as I could and adjust, unless I fancied the dismantlement of the connector side by way of experience, which would largely depend on alternative lighting.

 

[Ming the Merciless]

You can loosen the left hand side it has a locknut then the cone nut. Inject some grease, and then push the axel to the right and inject grease in the other side. A syringe from the pharmacy works well for this. Tighten up the left hand cone till there is no play, then back it off quarter of a turn, then tighen the locknut.

 

[Levo-Lon]

Thought you'd have the Flux Capacitor upgrade by now Andy..😁

 

[Ming the Merciless]

Thought you'd have the Flux Capacitor upgrade by now Andy..😁

He does but 88mph is proving a challenge