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I need help with an overhaul of the Shimano freehub that comes with the FH-HG50 hub (part no 30H 9801). How many balls go into the inner and the outer race? What size should they have?

I have already disassembled the freehub and counted 48 ball bearings in total. They fell out of both races simultaneously so I cannot say how many were in either race. Some look larger than others and I am unsure what their nominal size should be.

Edit: After servicing the freehub, I can confirm the correct size and number of ball bearings is 25 1/8“ ball bearings for each race, ie 50 in total.

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  • I misunderstood which part you have in mind. THe hub axle bearings have 18 balls, but the freehub itself has different ball bearings with different bearing balls. Do those 48 pcs include the balls in the hub itself or not?
    – Vladimir F Героям слава
    Commented Jan 27, 2023 at 15:16
  • Hi @VladimirFГероямслава I am asking about the freehub, not the hub. The 48 ball bearings are from inside the freehub and do not incl the 18 ball bearings (larger diameter) of the hub.
    – jaspb
    Commented Jan 27, 2023 at 16:37
  • I was also quite confused because for me a ball bearing is the whole piece that includes the bearing balls, the cone and the cup or the races and possibly a cage.
    – Vladimir F Героям слава
    Commented Jan 27, 2023 at 16:52
  • Sorry for any confusion caused. I explicitly asked about the freehub body ball bearings and not the hub.
    – jaspb
    Commented Jan 27, 2023 at 17:06
  • @VladimirFГероямслава that's a possible meaning, but "ball bearing" more often refers to the individual balls. The whole assembly would often be called just a "bearing" (or "cartridge bearing" etc. If appropriate)
    – Chris H
    Commented Jan 29, 2023 at 12:54

3 Answers 3

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Since Shimano freehub bodies are not officially meant to be opened and serviced, there is no exploded views nor procedures in dealer's manuals available on the manufacturer's technical documentation website to confirm the size and the number of ball bearings.

Still, a few Internet users demonstrated that opening an Hyperglide freehub body such as yours is doable and they reported that there were 50 ball bearings (25 on each side) of size 1/8" on their particular model. I suppose 48 balls as you counted is also possible since it is very close to 50. The difference in size you seem to notice might be due to manufacturing tolerance. I suggest measuring their diameter with an electronic caliper if you have access to one.

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  • Great, thank you for your answer. I assume 50 would be the correct number of ball bearings as I was able to fit 25 of the worn steel balls into the outer race and still had a bit of a gap when I tried to reassemble it the other day. I will go ahead and order 50 new 1/8“ steel balls then.
    – jaspb
    Commented Jan 29, 2023 at 15:10
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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 remained in service.

A popular YouTube bike mechanic, RJ the Bike Guy, has a video discussing the overhaul of a Shimano freehub body that I link to here. It should be helpful to get you through the process.

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    I've certainly counted 50 (2x25 1/8") in very similar shimano hubs. They're fiddly to service but it's quite doable.
    – Chris H
    Commented Jan 29, 2023 at 12:58
  • Thank you for the answer, Jeff. I only accepted the other one as it came in before yours. I appreciate the added context regarding wear and how it might affect perceived size and potentially number of the steel balls. Thanks for linking the YouTube video.
    – jaspb
    Commented Jan 29, 2023 at 15:11
  • @jaspb You're welcome!
    – Jeff
    Commented Jan 30, 2023 at 14:23
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One Youtube video in which a guy opened the bearing cones in a Shimano freewheel showed there were 39 bearings in the inside race and 31 in the outside race. This showed the bearings filled the race. I opened the bearing cone and found the inner race was pretty full and the outer race had about 20 bearings. I saw another video which was about the same as what I found. If there are 25 bearings in each then the inner race is only about 65% full. After greasing and reassembling the bike runs 100%. There is no real pressure on those bearing as long as a majority are in there.

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    Just a heads up, the original post is talking about the freehub body. The rear hub has two sets of bearings, one of them just inboard of the FH body. The FH body has its own separate set of bearings. Generally, Shimano sells those FH bodies as spares and I guess they assume you just replace those wholesale. Also, one bearing has one inner and one outer race (or cup and cone, in this case). It's not meaningful to say that the inner race has x bearings and the outer race has y, because an inner and an outer race form one bearing.
    – Weiwen Ng
    Commented Jul 7 at 22:48
  • Let's rephrase the my last sentence. An inner race, an outer race, the ball bearings, and the seal are generally considered to be one bearing. That can be in a cartridge or it can be cup and cone style.
    – Weiwen Ng
    Commented Jul 8 at 13:59

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