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Shimano Nexus 7 not shifting into lower gears + rust

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Shimano Nexus 7 not shifting into lower gears + rust

Old 02-06-21, 04:05 AM
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Andr33ii
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Shimano Nexus 7 not shifting into lower gears + rust

Hi, newbie here. My Nexus 7 got stuck in 6th and 7th gear and it doesn't want to shift down anymore but I could still ride it.
Cable seemed ok so I opened the hub up and discovered a lot of rust + gunk.
I tried cleaning it and then giving the assembly an oil bath, but it didn't solve anything.

Would you recommend taking the assembly apart and cleaning the rust with WD40 or something like that?
Or should I go straight for a new assembly? Nexus 7 seems to be pretty hard to get in Australia.
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Old 02-06-21, 08:05 AM
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Sounds like the hub needs more extensive rehabilitation. You could send it to Aaron's Bicycle Repair, though I realize that's very difficult from your location.

I have a couple Nexus 7 hubs. It's been a while since I did anything other than dipping the gear cluster in oil and greasing the bearings, but IIRC the gear cluster comes apart rather easily into several distinct sub-assemblies. These looked as if they could be disassembled if *great attention* were paid to the details. Pawls and springs could be removed and replaced after cleaning. I seem to remember that there are "timing" issues with the planetary gears, so correct reassembly is crucial. The one thing I *do* remember is that the central axle mechanism for changing gears should *not* be disassembled! I did this with one of my hubs and still haven't figured out how to get it back together. It's a "rainy day" puzzle for me, and I'll probably wind up sending it to Aaron's. You can get an idea of the difficulty level HERE. Sheldon Brown's SITE has a wealth of useful information.
Good luck!

EDIT: More HERE. Figures 16, 17 and 20 illustrate the "timing" issue. Figure 25 shows the modular construction of the hub; a single spring clip's removal (don't lose it!) allows this. You can probably clean the sub-units well enough without further disassembly. :-)

Last edited by sweeks; 02-06-21 at 09:43 AM.
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Old 02-06-21, 09:51 AM
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Originally Posted by Andr33ii View Post
Would you recommend taking the assembly apart and cleaning the rust with WD40 or something like that?
Or should I go straight for a new assembly? Nexus 7 seems to be pretty hard to get in Australia.
You could email those two experts for advice:
Bruce Dance
Dan Burkhart
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Old 02-06-21, 07:46 PM
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Thank you for your replies guys. Just discussed with my wife (it's her bike) and decided to try to resurrect this hub, even though it looks like it might be a long process and chances of success might be slim. We just need to figure out the space where to do it - we live in an apartment.
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Old 02-07-21, 08:08 AM
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Originally Posted by Andr33ii View Post
We just need to figure out the space where to do it - we live in an apartment.
You won't need a lot of surface area once the gear cluster is out of the hub, but I have found it handy to have the hub mounted in a vise for stability. Doesn't everyone need a small workbench?
Take pictures and post 'em when you can. I would rate your chances of success "good" as long as you don't mess with that axle unit!

EDIT: Something like THIS is quite helpful.

Last edited by sweeks; 02-07-21 at 08:13 AM.
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Old 02-07-21, 10:34 AM
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To give you an idea, here's how to take a Nexus 8 apart:

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Old 02-07-21, 10:35 AM
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The Golden Wrench: The Servicing of an Internally Geared Hub
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