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Old 12-08-10, 10:31 PM   #1
hybridbkrdr
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regreasing dynamo hub

Would you try to re-grease a dynamo hub yourself or is that something a shop should do? Or, would you try avoiding re-greasing them at all?

I read a message here somewhere saying someone had worked on a dynamo hub and ruined it. But I don't know whether he was just re-greasing or doing something else.
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Old 12-08-10, 10:46 PM   #2
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Which dynamo hub do you have? Service varies per product.

Check around and you'll be advised that the bearings on Shimano's dynamos (3N30, 3N71, 3N80, etc...) can be accessed and serviced on one side of the hub only. Trying to service the side with the connection terminal can result in damage to the wiring.
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Old 12-09-10, 01:35 AM   #3
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Oh, I was thinking about buying the T660 Deore LX version partly because apparently it has a better seal. And I think less drag compared to the 30 model.
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Old 12-09-10, 02:55 AM   #4
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The danger is that the connecting wire between the external socket and the internal generator is very thin, it is a non-rotating part and it lies within a slot in the axle. If you rotate the wrong piece you can snap the wire. You cant do any damage from the outside but once you open it up you can. There used to be some good illustrations somewhere on the net but I'm not sure where.
The Shimano technical documentation is no help at all.
My Shimano dynamo hub is about 3 years old. It is the XT grade version, well sealed and has never been opened. My LBS is reluctant to delve inside.
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Old 12-09-10, 03:09 AM   #5
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Really? If it hasn't been re-greased then how many thousands of miles do you think you can do before you need to re-grease them?
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Old 12-09-10, 09:51 AM   #6
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SON hubs say 50,000 k.
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Old 12-09-10, 01:18 PM   #7
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Quote:
Originally Posted by hybridbkrdr View Post
Would you try to re-grease a dynamo hub yourself or is that something a shop should do? Or, would you try avoiding re-greasing them at all?

I read a message here somewhere saying someone had worked on a dynamo hub and ruined it. But I don't know whether he was just re-greasing or doing something else.
Assuming a Shimano generator hub, then it can be done, but shouldn't be attempted unless there is a very good reason.

The problem is the "current wire" running from the inside rotor, out through the slotted axle ending in the connector. Because of this it is vital that the connector doesn't move when unscrewing the locknuts/cones. When taking the hub apart, the connector should remain stationary to the axle the whole time (hold it down with a finger while using the cone spanners). Besides that it is just a standard cup-and-cone hub. Another problem is that the "current wire" is a thick copper wire. It only takes that many bends before snapping apart. It can also get snagged when screwing the cones on again.

One side of the hub can be serviced without problems, but get a feel for how the hub feels because the magnets makes cone adjustment more difficult.

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Old 12-09-10, 01:25 PM   #8
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SON hubs say 50,000 k.
SON hubs use sealed cartridge bearings and the importer has the tools and knowledge of how to replace the bearings if there is a failure or they need service.
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Old 12-09-10, 01:49 PM   #9
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SON hubs say 50,000 k.
My SON started to produce grinding noises only after about 10K miles (would have to check records to come up with more precise K number) and got swapped with one that just underwent an overhaul.
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