Lately my gears would stick a bit and i started to hear a grinding noise. While taking the rear wheel off I noticed that the sprocket felt like a ball bearing was overtightened, having quite some resistance.

Lo and behold, the whole hub was full of rusty water. How could this happen? Am i missing a seal?

I've always taken reasonable care of the bike, with sheltered (upright) storage, and I never wash it with a hose precisely to prevent this problem.

I never had any maintenance done on the hub, the sprocket has been replaced once but you dont need to take the hub apart to do this.

Hub is about 5 years old.

Edit 1

It's a Shimano Nexus 8-speed.

After taking the whole thing apart I didnt spot a single seal. No c ring or o ring on either side. Does anybody know where it is supposed to be? There is just a loose fitting dust cap on the sprocket side.

Edit 2

Thanks for the comments and answer! This gives me confidence to invest some sweat in cleaning everything and polishing the damaged surfaces. If someone in the future plans to do the same thing, there are some great dis/reassembly videos on youtube Ive found.

Edit 3

After cleaning and polishing every part and putting everything back together (aligning sun gears is a nightmare I have learned) with loads of grease my ride is once more as smooth as silk!

Apparently there are no proper seals on such a hub, just some loose fitting dust caps and a grease barrier, so I'm going with the accepted answer that the grease barrier was insufficient.

Lots of credits to this guy and this guy for uploading very helpful assembly videos. Even though my make varied slightly from both of them I was able to figure everything out thanks to their videos.

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  • 5
    Has it been in the rain a lot, especially lying down or with wind as well, or exposed to a lot of spray from passing vehicles? Has it been washed recently (and how)? Have you ridden through any fords? You have more clues than us, to help narrow it down. But there's also a chance that seals aren't what they should be
    – Chris H
    Commented Apr 22 at 21:02
  • 2
    How do you store the bike - do you take it from a warm environment to a cold one? Cool causes the air pressure drop inside the hub, If there's water around the seals (e.g. from rain/snow etc, water gets sucked in.
    – mattnz
    Commented Apr 23 at 3:43
  • 2
    What kind of hub is it? Looks vaguely like a Shimano alfine or nexus ?
    – Criggie
    Commented Apr 23 at 5:57
  • 2
    All great comments, excuse my tired head for not doing a better job on writing the question, ive updated it!
    – Sebastiaan
    Commented Apr 23 at 6:56
  • 2
    Page 102 here has a full parts list and explosion diagram: si.shimano.com/en/pdfs/sm/IHG-INTER8/SM-IHG-INTER8-001_ENG.pdf The only seal seems to be “13. Y37J98080. Right Hand Cone w/Seal” I’d check all the bearings for damage and then re-assemble with plenty of nice, thick bearing grease. Water can’t go where grease is.
    – Michael
    Commented Apr 23 at 7:20

1 Answer 1


According to Sheldon Brown on Shimano 8 speed hubs:

Probably the most common failure, though, is due to insufficient lubrication, leading to contamination by water and dirt.

and later...

The right-hand hub bearing cup is vulnerable to damage from water contamination. Factory lubrication is inadequate, and better lubrication is advisable -- even with a new hub -- also, to make later cleaning and rebuilding easier.

I think the bottom line is that these hubs are prone to picking up water and dirt due to less than adequate seals and poor lubrication from the factory.

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