[Closed] Another shimano bb bites the dust

Deore isn't particularily good but should still last longer. How confident are you that you're not overtightening?

When you take the BB out,is there water in the frame?

No water that I remember, don't think I'm overtightening but ordered a new one and will check for water.

Without trying to be smart, have you considered buying one from a shop and having them fit it? If it lasts longer than your DIY ones then you could look at why.

IMHO you don't need to jet to damage an external bb with water, all tubes lead water to the bb and the top hat & crank arms spider and rings with surface tension help to keep it there. The bearing then rust from the inside. If you must hose have the bike upside down as most saddles have no moving parts 😉 or make a conscious effort to dry off the bike afterwards.

I would go and get your frame faced in the first instance. Sounds like it could be a cause?

Frame carbon so no facing, worked in an lbs so fairly confident I'm fitting it correctly. Just trying to find out if there's something I've overlooked

I tend to kill one after a few wet rides. Problems of an external bearing.

My bikes get hosed down occasionally, then left to drip-dry in the garage. I have perfectly functioning Shimano BBs (including a Deore one that must be 4 years old).

I know you reckon it doesn't need facing but is it possible the BB shell is somehow out of alignment (tricky without seeing your frame)?

The RaceFace BB on my fatbike has so far lasted 18 months. It has easily done a couple of thousand miles, has been submerged in both fresh and salt water, dragged through highland peatbog, had me bouncing around on it and when I checked it all yesterday was still spinning freely. I'm not buying that there is something inherently faulty with the design of external BBs.

I tend to kill one after a few wet rides. Problems of an external bearing.

My bikes get hosed down occasionally, then left to drip-dry in the garage. I have perfectly functioning Shimano BBs (including a Deore one that must be 4 years old).

These both confirm what I've been thinking/experiencing. My cx bike's bb shell prob does need faced but it goes through a few bbs in a season. That said my deore bbs seemed to last a hell of a lot longer in the past than they do now but I wondered if that was my rose tinted glasses. I shall tighten and lovingly attend the incoming bb and see what happens. Replaced with a king would be my suspicion.

Pimpmaster Jazz - Member

I tend to kill one after a few wet rides. Problems of an external bearing.

But most people don't kill them after a few wet rides, so it can't be just an inherent issue with the design.

I just replaced the NDS XT one in my Ragley- fitted the BB when I got the frame, it was previously in my C456, and so was about 9 months old and got ridden constantly. It has not been a very dry summer, autumn, winter or spring in Scotland 😉 The DS one is still fine, the NDS one had gone loose.

If you're going through Shimano ones fast, you might want to look at the Gusset EXT24- it lasts only a little better without servicing, but is easily dismantled to clean/grease bearings, or to replace them, and uses standard bearings, and doesn't cost much more.

Alternatively, continuing my overtightening theme- Hope are far more resistant to home mechanicking than Shimano 😉

[i]Just trying to find out if there's something I've overlooked [/i]

Yep, replace this time with a Hope.

mine got stiff after a very wet trip to dalby (ahem)

I'm going to follow [url= http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/outboard-bearing-bottom-bracket-service-guide-pics-497220.html ]this guide[/url] to try and salvage it as i refuse to believe you have to throw away something that quickly

My suggestion is firstly carefully take out the top hat and outer bearing seal, try and get more grease in there on the new BB.
Secondly the preload really doesnt need to be tight, if you look between the non drive crank and the tophat, you should see the gap close up when preloading. As soon as it has closed back off an 8th of a turn and tighten the clamp bolts.

if your carbon frame takes a threaded bottom brakcet that does not exclude it from being faced.

Yeah I'm going to buy a king when money allows, seems like they're just much easier to service. I genuinley don't think I'm overtightening, I'm not strong enough 🙁

I could press some Enduro bearings in for you, if you send me your cups.

nsfweb at me dot com

Also this

bigyinn - Member
Secondly the preload really doesnt need to be tight, if you look between the non drive crank and the tophat, you should see the gap close up when preloading. As soon as it has closed back off an 8th of a turn and tighten the clamp bolts.

fontmoss - Member

I genuinley don't think I'm overtightening, I'm not strong enough

Bearing preload is fingertight on most Shimano cranks!

Shimano external BB's last me over a year of riding Scottish mud and gloop at least once a week

Yeah I know about the preload, it was a joke 😉

Shimano external BB's last me over a year of riding Scottish mud and gloop at least once a week

Dave - I faced mine. Worth doing. Bonded in Alu section to face......

Ahhhh

Just been de-winterising my multipurpose Frankenbike (on/off road commuter). It has a 2yr old Deore external BB that's as smooth as a very smooth thing. Just cleaned it and the cranks up and popped 'em all back on - perfect.

If its any consolation I have to clean/re grease my BB on my SS at least once a month at the mo, even then it's a bit creaky on hard climbs. I'm not changing to my new BB until the summer hits hard.

My current XT BBs are about 2.5yrs old - they got lashings of grease when first installed and every so often I reapply some more. Seems to work.

(never faced and hosed a plenty)