Shimano Nexus 8 Speed Hub Reassembly - Putting It Back Together...

I was challenged by my viewers to try to re-assemble the Shimano Nexus 8 Speed Hub that I disassembled in my last video. The hub is a Shimano Nexus SG-8R20. Fortunately, I had my video of taking the hub apart, which helped me in figuring out how to put it back together again.

Shimano Nexus 8 Speed Hub - Dissection! Evisceration! Destruction!:

Here is the Shimano service manual:

For assembling the shift spring assembly, this video by Dan Burkhart was greatly helpful:
Shimano Alfine shift spring overhaul

* editing goof at 16:55 to 18:34 with one clip, and then a reshot version of the same clip. I redid it because I thought I could show it better. A little peek behind the curtain of shooting one of these videos.

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[billd]

As a Merchant Marine Engineer for more than two decades I’ve overhauled all manner of complex machinery (motors, pumps, purifiers, valves...) but this really challenges your attention to precise assembly. I watched you take this apart, and I was reminded of the old engineering saying that “assembly is never the reverse of disassembly”. Anyone can take stuff apart. Putting it back together is always the challenge.
Bravo RJ, I could have used you on the ship.

[mangoie]

Hey RJ. I had a shifting problem with my Nexus 8, so I found this vid while I was looking for a possible solution. Thanks for such this detailed video, I learned a lot! <3 So my problem was that gear 1-4 and 5-8 were the same (despite shifting), and after watching this video a couple of times I found the solution, maybe it can fix your problem too!
Gear 1 and and 5 use the pawls of the carrier unit (15:22) to transfer the power of the planetary gear system to the body of the wheel (24:09), sort of direct drive. However, if you use any of the other gears it actually uses something else to transfer the power of the planetary. The thing you call a ring bearing at 17:41 is actually a "roller clutch" that engages into the wheel body in gear 2-4 and 6-8. The spring/ring you install at 17:03 not only keeps this roller clutch in place but also rotates it so the "rolls" of the roller clutch can extended and retract (=drive or roll free). Make sure after assembling the carrier unit that the roller clutch can rotate a little bit without too much effort (the tab of the clutch should move in the notch at 16:34) and make sure the rollers are moving a bit radially. Carefully, because the ring/spring that keeps it in place goes loose pretty easily. I also removed a bit of the excess grease of the smooth part of the body of the wheel (24:09), I would think that much grease would just let the roller clutch slip. I would not be surprised that a lot of people have problems with this hub after a quick re-lubrication because this roller clutch slips after applying too much grease in the wrong places. Anyway this made it work for me flawlessly again. Hope it helps you and other people!

[Antje-Pikantje]

I enjoy repairing stuff on my bikes because they are always very simple mechanical things.
This thing however is just unbelievably complicated. Thanks for showing how to take it apart and back together. Even if it still won't work properly, you are my personal hero!

[AntonBabiy]

I find it amazing how they design these things! So complicated

[davidrjamieson]

Thank you for the detailed video. I was able to fix mine after many attempts. The second spring insert is the trickiest part, and it is what was wrong with mine. The spring has to be inside the upper flange tabs, and outside the lower flange tabs after you tighten it one turn, but it does not want to do that! Several times I thought I had it, but I couldn't get both sets of four gears to work. Upon inspection, I could see the spring was crunched up in the space, but not properly, so the mechanism that gave you the second set of gears was not moving properly. Finally, I had to ask my wife to help, and with four hands available, we got it in correctly, and now it works. Thank you!

[Heleninhalinda]

Man, as a cyclist and bike mechanic I absolutely love ur vids. I very very rarely enjoy any YouTube video longer than 20 mins, but you 40min+ vida makes me thrive

[edriley]

the complexity of this hub is a-pawling and your stick-to-it-tive-ness to be applauded. keep at it. get those pawls aworking and astonish us

[josjetwentytwo]

I really enjoyed watching. Two years ago I fucked up a very dirty shimano 3 speed hub from my sons bike. I thought, well I can do this! I Watched reassembling videos but at the end it diden't work. Finally I bought a 2nd hand inner work for less and finished the job. Could not sleep for 2 nights, felt very disappointed in my skills. Your video reminds me about that my struggeling moments with the shimano hub. BUT, I really got BIG respect for the engineers who invented these hubs with so much parts, all designed with a purpose and all work together. Me myself, I am am audio/video composer but when I got a BMW R60/5 (1971)from my dad 15 years ago, I started to appriciate the wonderfull world of mechanical enginering. Great Video !!!

[rewind]

Thanks for another great video. I obtained a Nexus hub for just about free but was it frozen and rusted. I took a little apart, and got it shifting, but the pawls would not engage. More disassembly and eventually all working good. Your video was the best on YouTube with careful and clear explanation of the assembly. This was probably the most complicated assembly I have ever performed and would of never got it completed without your detailed video. Thanks, RJ!

[sitflyer]

and they said nobody could put Humpty Dumpty back together again! Well done!

[FozzyS]

Now you're an authorized Shimano IGH mechanic. LOL! Nice job RJ!

[brindlebot]

Really appreciated this vid for my Nexus 8 service. More parts than I thought which would have been impossible to put back together without this video.

[ralphievelasquez]

Great deal of knowledge... patience and integrity..RJ you are a very smart man.

[nickandersonco]

In the first video you didn't have a clue what you were looking at, now you have all the tools and can do the majority of maintenance on those, as well as a decent amount of troubleshooting. Very impressive and inspiring to watch.

Thanks again!

[rogerduncan]

Thanks for the great video. THE PAWLS ARE WORKING FINE! They don't get pulled down! They just get overridden by the shell because it moves faster in higher gears so the lower gear pawls just slide underneath while the correct pawl grips. I think if you tried this hub it would work fine!

[MrLuigi-oigm]

That was the most suspenseful video/movie I have ever watched! Will RJ succeed? Will be not? You did it!!! Take a huge bow RJ! That was so interesting. Can't wait for the sequel where you do battle with those stubborn prawls!

[classydays]

Kudos to whomever designed this thing, but rebuilding one deserves a beer

[diavalus]

6 months ago, I tried to service the same hub. Guess what, I've had the same issue and I gave up after a while. Anyway, cheers for your effort of putting everything back together!

[johnburton]

If anyone can do it RJ definitely can. RJ you're the man love the videos keep them coming

[adrianharding]

Great video RJ. I was a bike mechanic when I was younger. When one of these things showed up at the shop it really separated the guys that thought they knew (me) from the very very few that did. Your video was a great aid to me while servicing a nexus 8 with lots of drag. Thank you for putting this together.