Freehub Body Disassembly/Assembly
Why Bicycles Stack Exchange recommends it
Bicycles Stack Exchange answerers point people to it when someone needs to overhaul a Shimano freehub body, since Shimano treats them as non-serviceable and few written guides exist.
Recommended by 5 people across 5 different months, 2018 to 2023.
What it is
RJ The Bike Guy walks through taking apart a Shimano freehub body, cleaning and lubing it, fitting new 1/8 inch bearings, and putting it back together. He notes that freehubs are normally replaced rather than serviced, but a rebuild can save a hard-to-find part.
What people said
Recommends aspseka · 2018-03 · Bicycles Stack Exchange · on “Old Shimano Altus Hub disassembly. Clockwise or counter clockwise?”
It is left-threaded, turn clockwise to loosen. On some hubs the attachment bolt that fixes the freehub to the hub also locks this bearing cup, make sure to loosen or completely remove it before attempting to unscrew the cup to avoid destroying its threads. While often not necessary to overhaul (especially given that the bearings don't take much load and in almost all cases you won't get hold of spare pawls), it is actually not that hard to reassemble. Make sure you disassemble slowly and keep the bearing balls of each bearing separate (25 balls, each). There is also a video [this video] on youtube that shows the process.
Recommends Robert · 2019-02 · Bicycles Stack Exchange · on “What tool do I need to remove this Joytech freehub?”
Cleaning and greasing is rather complicated, you might need fancy tools. See this video: [this video] I removed it because it was making a slight grinding noise, but then I found out it was not big deal so I put it back on, 2000km since then and it's working perfectly and the grinding noise disappeared.
Recommends Jeff · 2023-01 · Bicycles Stack Exchange · on “Number and size of freehub ball bearings for Shimano FH-HG50 (30H 9801)”
This older model freehub body can be overhauled. The bearing size is 1/8" and a 25 count for both the inner and outer races (50 1/8" balls total). Often times, extreme wear of a loose ball bearing system can yield what appear to be differing sized ball-bearings. They started out life as the same diameter, but uneven wear, brinelling of the races and dirt ingress create a situation where there is uneven load so wear at any one ball can be much different than for another. I've seen bearing balls come out where the outer layers were peeling away like an onion. Other times I've seen balls that have fractured and the larger piece became rounded (albeit imperfectly) again from wear as the bearing
Recommends olliebulle · 2023-02 · Bicycles Stack Exchange · on “How do I get off my totally stuck freehub body?”
Just to be clear, the part shown on your pictures is called a freehub body (black cylinder with splines). It incorporates the ratchet system enabling the hub to engage one way and to disengage the other way. This is where you attach the cassette. A freewheel, on the other hand, is a single part that combines the ratchet system and the sprockets. (I edited your question to update the wording) A freehub body can definitely need to be replaced if the internal bearings are gripped or show excessive loose. You would need to use an hexagonal/Allen wrench of the correct size (e.g. 10 mm) to unscrew the fixing bolt in the middle to remove it. One good way if it is stuck is to clamp the hex wrench in
Recommends sellotape · 2023-10 · Bicycles Stack Exchange · on “Shimano freehub body replacement compatibility”
Just to close this off... At the time I looked into it quite a bit, and as the AliExpress link [LINK] posted by @elad-schitrit implies from the number of options, I found that Shimano has over time made a lot of very-similar freehub bodies (even, it seemed, within 10 speed splined), each with potentially slightly different dimensions. Eventually I concluded it wasn't worth pursuing further. The linked answer [LINK] in my original question mentions many of the same concerns. At some point I'll just get a new wheel with a better hub... So I ended up servicing the freehub body instead, which turned out really well. No additional POE though. Here a video [this video] if you want to go that way. I als
Cites Jeff · 2023-05 · Bicycles Stack Exchange · on “What is the quantity and size of the ball bearings in Shimano M785 freehub?”
Here is the Exploded View of the Shimano M785 rear hub [LINK] . Note that the right, drive side uses 13 loose ball bearings size 3/16 inch. The left, non-drive side also uses 3/16 inch bearings but they are contained in a plastic bearing retainer. You can certainly use loose balls on that side too. Simply fill the race to capacity and then remove one ball. You're likely to use 13 loose balls there or a count of 11 in the retainer. If it the actual freehub body you wish to service, you should know that Shimano states that their freehub bodies are not serviceable but are sold as replacement parts. Googling "freehub body for FH-M785" yields many results from a variety of sellers for this partic