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bearings, bicycle crank, where is the grease seal?

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bearings, bicycle crank, where is the grease seal? werwer 05-07-2008
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Posted by werwer on May 7, 2008, 11:15 pm
I have an 15 year old bike and the crank bearings gave out due to lack
of grease. I cleaned everything up and replaced both. These are open
ball bearings in a light stamped cage. I greased the snot of them but
wonder how they hold it. There is no backside seal, backside as in
towards the center of the crank, and it would seem the grease would
just flow away.

I filled the whole area with grease but, is there a seal missing,
something to hold the grease in the bearings?

Two didn't fall out when the bearings crumbled in my hands, which
doesn't mean they shouldn't be there. Bearings did last 15 years
so ... so what :-) (The new stuff is all sealed up and comes as one
cartridge you just screw into the crank frame cylinder.)

Posted by David L. Martel on May 8, 2008, 8:29 am
werwer,

It's been years since I messed with a bike but I do not recall any seals
in the crank. The wheel bearing grease is fairly viscous and probably does
not flow much. The forces involved during pedaling are not likely to fling
the grease off. You're probably ok for another 15 years. You could ask a
bike shop.

Dave M.



Posted by RicodJour on May 8, 2008, 11:32 am
> I have an 15 year old bike and the crank bearings gave out due to lack
> of grease. I cleaned everything up and replaced both. These are open
> ball bearings in a light stamped cage. I greased the snot of them but
> wonder how they hold it. There is no backside seal, backside as in
> towards the center of the crank, and it would seem the grease would
> just flow away.
>
> I filled the whole area with grease but, is there a seal missing,
> something to hold the grease in the bearings?
>
> Two didn't fall out when the bearings crumbled in my hands, which
> doesn't mean they shouldn't be there. Bearings did last 15 years
> so ... so what :-) (The new stuff is all sealed up and comes as one
> cartridge you just screw into the crank frame cylinder.)

If you used the right grease, such as Phil Wood's waterproof stuff,
you're good to go.

R

Posted by the_tool_man on May 12, 2008, 12:42 pm
Sealed bottom bracket bearings exist, but are uncommon. The grease is
typically viscous enough not to flow out of the bearing. Just after
assembly, you'll get a little squeeze-out, which can easily be wiped
off. It should be fine after that. I only use Phil Wood waterproof
grease, which is supposed to be better for this sort of thing.

Of more concern is the possibility of contaminants entering the bottom
bracket from other places in the frame. Lots of older and new cheap
bikes have no sleeve in the bottom bracket, so anything that finds its
way into the bike frame can drop into the bottom bracket. If you have
internal cables, unused braze-ons, or an opening in the top of the
seat tube, water and dirt can easily get in. I take an aluminum 12oz
soda can and cut a metal strip wide enough to just fit between the
outer bearing races. Curl it tightly enough to slip between the races
and allow it to spring outward against the inside of the bottom
bracket. Works like a charm.

Regards,
John.


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