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You know the ones, they say "Do Not Disassemble" on them.
For those of you who have taken them apart, I have a question. They are only sealed on the inside with the two piece tophats on the outside. Anyone thought it might make sense to put the bearings in "the wrong way around"?
An extra seal on the outside and the inside face should be protected by the centre tube.
Your thoughts?
No tinkerers home yet?
Don't recall that on the one's i've taken apart, seem to remember them being double sealed. Maybe the newer/cheaper ones aren't?
The one I took apart last night was from a FC-M532 chainset/bottom bracket. If you think "seal" in terms of the snap in type normally found on deep groove ball bearings, then it was only sealing on the inside. Outside face had a shield and top hat. Might explain why they only lasted 18 months.
Thought I had something similar on XT jockey wheel, turned out that dirt trapped between the seal and shielding washer had ground the outside rubber away leaving just the metal backing.
Could be that. I'll have a closer look. There's a lot of muck in there.
Okay, so the new bottom bracket has arrived with a fc-m542 chainset. I've popped the bearings out as the plan is to clean and re-pack them. I'm not looking to open up the whole issue of should you lift the seals. I'm going to, simple as that. There's something else going on here.
From out side to inside there is: -
Top hat.
Rubber faced metal shield that clicks into top hat.
Open and exposed bearing face
Conventional seal on the inside face which reads Sunhill, 6805-RD, A326.
Now, as there's a sleeve linking the two cups and sealed with O-rings, I'm tempted to think these would last better with all the sealing facing out. In theory, there may be a small amount of water that seeps in between the axle and the top hat but I'm fairly convinced the damage occurs from the outside in.
Any thoughts? Ideally, the bearing would be 6805-2RS but that's not happening.
why not 6805-2RS [url= http://www.google.co.uk/search?source=ig&hl=en&rlz=1G1GGLQ_ENUK346&q=6805-2RS+bearing&btnG=Google+Search&aq=f&oq= ]??[/url]
It would make sense, but what I mean is that Shimano didn't supply hem with a 2RS bearing. Only one side is sealed. The question is, would that seal be best on the inside or the outside?
By the way, it's not a real 6805 as most people know it because the bore is 25mm rather than 24mm, hence why/how they use a top hat.
eh? 6805s are a 25mm ID theyvwork as a straight replacement... no need to replace your whole BB and you can fit 2RS ones if you want...
Shimano probably only leave a seal out on cost grounds and/or to reduce drag maybe...
Sorry, you're right, it's Hope and others who use the non standard bearing to sit directly on the 24mm shaft without a tophat/spacer.
Anyway, I'm not looking to replace the bearings in this shimano cup, they're brand new so I might as well run them to destruction first as I've got them.
My point is, they are supplied with only the tophat/shield on the outside and a proper seal on the inside.
Wouldn't it be better to pop the bearings out and turn them around so all the sealing is on the outside?
why not buy the 2rs replacements now and use one of the seals from them or get one extra & sacrifice it for the seals ?
(I assume they'd fit)
The original shimano bearings are only lipped on one side so there's no way to add a seal even if you had one. Just seems to me that the seal would be more use on the outside.
give it a go 🙂
(people seem to kil the drive side first, so swap that one & leave the other normal & see how they go ?)
It didn't work in the end. On closer inspection, the Shimano bearing is far from standard. It only has a lip for a seal on one side. On this same side, it also has a recess on the bore of the inner race. The recess is for the bulge on the tophats to locate into. This is why they "snap" into place. Turning the bearing around would then have made the top hats a tight fit on the axle.
So, I just stuffed everything as full as I could with silkolene RG2 grease. That should help it along a bit.