bearings, bicycle crank, where is the grease seal?

[werwer]

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.)

[David L. Martel]

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.

[RicodJour]

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

R

[the_tool_man]

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.