Filling the BB CAVITY.

[HowardSteele]

Howzit,

I got a shimano; OCTOLINK/BB and having just replaced it I’m trying to prolong the life of the new BB.I have noticed a fair amount of water got into the space around the bb, with dust a destructive agent. I have a screw hole below the Hub, to secure a cable guide and when i remove the screw after a wash it acts as a drain. Now my questing could i pump silicone in through this screw hole filling the cavity and probably keep the BB a lot drier?

The silicone should gel around the BB and should come out as a tube the shape of the cavity on removal. Any comments?

Cheers Howard.

 

[lumpy]

I'd find and plug the holes that allow water in and keep the "drain hole" unplugged.

 

[davebee]

I'd find and plug the holes that allow water in and keep the "drain hole" unplugged.

agreed. when the screw is in place and the BB is fitted, the whole area should be a sealed environment.

 

[HowardSteele]

You would think so, maybe shimano should call their sealed BB, a semi sealed BB.

When it is locked in place with the lockring,water can still enter the cavity, That being the BB tube, On reflection the water running into the BBtube and me draining it periodically probably will be the best option, the screw is a fixing screw so it can't be left out. And I’m not drilling another hole to act as a drain.

I’ll probably have to remove the bb and repack the bearing with waterproof grease every couple of months. I can’t say I’m to impressed with the XT shimano BB SETUP, and when I have to replace the crank and chainring assembly I’ll probably go for the newer method.

 

[AKTed]

The Shimano Octalink BB are not known for long life. But they are sealed units - the bottom bracket that is. The bottom bracket shell is another matter. There are numerous ways for water to enter the tubes of a bike and migrate to the bottom bracket area. As lumpy said, some even advocate that you should have a small hole in the BB shell to allow it to drain. I would not pump the void with silicone. It would be mess the next time you want to change out the BB. And it could essentially trap water that could othewise drain out by removing the screw in the BB shell. On most conventional bikes there are holes from the BB shell to the chain stays and there are usually small holes in the chain stays near the drop-outs, so if you hang the bike up by the front wheel then most moisture should drain out that way. At least that is what I have read.

 

[moparchris]

ok firstly you wont plug the holes to stop water getting in in the 1st place, there are usually heaps of small holes for ventilation when the frame is welded togeather, theres the seat tube, water gets down there and i suppose you could stop it with silicone but thats gonna add weight and youll probly get your post stuck. Second shimano BB's are sealed bearing units that doesnt mean they wont get dirt and water in them, water cant actually get into them from inside your frame, if you look at it water would have to seep out through under the LH cup and then get into the bearing from where on the outside you can see the seal, thats why they have a seal on the inside of the LH cup and the RH side is part of the main sealed unit so water cant go through that way. So the water going through your frame isnt going to do anything to your BB except probably make the shell rust over time. If you fill your frame with silicone all its going to do is make the frame hold water and add weight, drill a drain hole in the bottom of the bike, most good bikes come with one and if it doesnt have one, add one. it doesnt need to be very big and will take you like 2 seconds.