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Belt drive Gear/Brake hub FUBARd - Need Solution

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Belt drive Gear/Brake hub FUBARd - Need Solution

Old 06-23-23, 12:06 PM
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Belt drive Gear/Brake hub FUBARd - Need Solution

Hey guys,

My errand bike is a *belt drive with a Nexus *three speed hub with *internal hub brake (drum or roller, not sure).

The internal gears are slipping and clunking almost too badly to use the bike anymore.

To say these hubs are hard to find would be an understatement. My LBS said they were probably a custom order.
Even chain drive hubs w internal brakes aren't in "the catalog."

Any solution that's even arguably cost effective or do I have to junk thing?

It's got integrated lights, rack, fenders, and anti-theft features so I'm not likely to find a suitable replacement without spending a bundle, if at all.
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Old 06-23-23, 02:53 PM
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What exactly is going on and what have you done to fix it? Has the bike ever seen service? Especially the hub? It does use oil inside of the hub and does need to be replaced with some regularity and if you don't do that it can cause issues inside. In the end I would see if it is serviceable and if nothing else as long as the hub shell is in decent shape you can sometimes get internals from Shimano or a new hub and replace the internals and then just like anything maintain it at regular intervals and it will last longer.

People unfortunately have this myth in their head that a belt drive IGH is maintenance free and that is not the case at all it is just lower maintenance but still you need to do a normal annual tune up and oil bath for the hub at some regular interval.
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Old 06-23-23, 03:48 PM
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There's no reason to assume the worst until you do a proper diagnosis. It might be a simple adjustment, or the internals may actually be damaged beyond repair.

Keep in mind that the drive side is separate from the cable actuated brake, so it may be possible (or may not be) to replace the internals as a module taking them from the comparable non brake version of the hub. That saves the cost of a wheel and preserves the brake function you're happy with.

BTW - Dan Burkhart is an EXPERT on Nexus hubs who posts regularly here on BF. He might give you solid advice or you might send the wheel for the internals to be serviced or replaced. Note that he's in Canada, so unless you are also Canadian, logistics may be problematic. Hopefully, he'll see this and respond with solid advice, but if not you can reach out to him through BF.
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Old 06-23-23, 04:12 PM
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did the LBS dig into the hub any or just searched for a replacement?

Does it make the noise/clunking only under load? Not too familiar with those. I'd be curious what the internals look like.
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Old 06-23-23, 04:20 PM
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You should find a better, more qualified bike shop.

https://www.modernbike.com/shimano-n...ernal-assembly

I took a random guess you had the 3C41 unit.

These things are essentially bullet proof. Have you placed the shifter in "2" and made sure the yellow indicator in the bell housing at the hub is between the 2 lines? How goes the friction in the shifter, housing, & cable?

Next up is the shifting pin can be susceptable to damage from poor care taken during wheel/shifter install. It can usually be carefully straightened & reused. The shift rod is inexpensive & readily available. Just make sure to use the proper length. https://www.modernbike.com/product-2126203970?TID=394

Lastly, you do make sure to pause pedal force for a brief moment to allow the shift to cleanly & smoothly happen, correct? You don't have a clutch. Power shifting can cause all sorts of mayham.

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Old 06-23-23, 05:30 PM
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Many thanks for all the replies.

The LBS did not open up the hub. Maybe I can find a better shop. Although maybe I can't. The closest one to me wouldn't even look at the bike, another supposedly higher end one had to google how to replace the belt. This guy at least was nice and trying to be helpful. I'm a so-so mechanic, playing with the internals is probably beyond me.

Doubt it's a 3C41 b/c it's not a coaster brake. It's cable actuated. I'm not sure if it's roller or drum.

It skips/clunks under load in all three gears. (It's not an issue of shifting or of slipping in or out of the selected gear.)

It's sealed. Unlike the old S-As I used to have there's no cap or fitting for lube service.

Of course servicing would be best if possible but I'd spring for a wheel rather than have the bike become useless.

Thank you again.
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Old 06-23-23, 05:50 PM
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Located the part number: SG-3R42
Guess that's a good lead. There are a few on ebay from non-US sellers.

Last edited by zowie; 06-28-23 at 10:47 PM.
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Old 06-23-23, 05:57 PM
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Originally Posted by zowie
Hey guys,

My errand bike is a *belt drive with a Nexus *three speed hub with *internal hub brake (drum or roller, not sure).

The internal gears are slipping and clunking almost too badly to use the bike anymore.

To say these hubs are hard to find would be an understatement. My LBS said they were probably a custom order.
Even chain drive hubs w internal brakes aren't in "the catalog."

Any solution that's even arguably cost effective or do I have to junk thing?

It's got integrated lights, rack, fenders, and anti-theft features so I'm not likely to find a suitable replacement without spending a bundle, if at all.
I would not be in a rush to find a replacement without first doing some trouble shooting.
The symptoms you describe may very well be caused by improper shift cable adjustment, worn or sticky cable or improperly installed bell crank.
Page 34 of this document is a trouble shooting guide.
https://si.shimano.com/en/pdfs/sm/IHG-INTER3/SM-IHG-INTER3-002_ENG.pdf
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Old 06-23-23, 06:10 PM
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Further to above, I would start by ensuring the shift rod is moving freely and returning to its default position. This is done by removing the bell crank and pushing the rod into the hub and ensuring it springs back. It is a good idea at this point to remove the rod and lubricate it.
After re installing the bell crank ensure that the little indicator in the window is between the two indicator marks with the shifter in the second gear position. If it is not, adjust the cable until it is
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Old 06-23-23, 06:26 PM
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From the picture, roller brakes are the kind that fit your hub. Coaster brakes have shoes that fit inside the hub shell. Drum brakes don't really exist for this application, and Band brakes thread on 1.37inx24tpi threaded shell. Your bike has roller brakes & all kinds from the lowly inter-m all the way up to the very capable C-6000 will fit. The only choice is: "How much heat capacity do you want?" Be sure to service with Moly-diSulfide grease at the first sign of lost modulation or at least a squirt or 2 at least annually.

If you do need to replace the guts, it's not complicated. Anyone who has swapped out an axle will have the necessary skill. Clamp the axle in some soft-jaws, in a vice. Remove the axle jam nut & cone on the drive-side of the axle. Lift the wheel away from the guts. Reverse the process on a new cartridge. Adjust bearing preload just until no free-play can be detected at the rim. Done.

Be sure to replace the balls & use a compatible bearing grease. Squirting in a bit of 90 weight oil into the cartridge during reassembly isn't a bad idea, IMO.

Last edited by base2; 06-23-23 at 06:29 PM.
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Old 06-25-23, 12:27 AM
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Great. Will try some of that. Thank you all.
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