Kdarmy

I just had my BB replaced at my LBS due to a faulty unit and all was good for 2-weeks, then today I get home and notice there is a crack at the one o'clock position on the non-drive BB cup. I will be taking it back to LBS tomorrow.

The bike (Raleigh, Passage) is still under warranty, so thats not a problem. Is there anything I need to discuss with the shop when I drop it off? Is there a better BB replacement which could be used? I wouldn't mind dropping the extra 10 bucks or so if there is a better upgrade of some sort.

Is this a common problem or like most times...is it just me?

Thanks,
Keith

HillRider

What brand and type is in it now? Shimano uses a plastic nds cup for some of their square taped cartridge bottom brackets and, if installed badly, these can crack. It's not a major problem.

Retro Grouch 

The problem is that it's not a cup. It's just a spacer to keep the bottom bracket from tipping. You don't have to torque those things on like they hold the whole bike together. They just have to be tight enough so they don't come unscrewed.

DMF 

Don't worry about the crack. It's not a problem.

Coyote!

Actually, I've worried myself silly over those Shimano plastic non-drive side cups. What happens if you snap one while trying to unscrew it? Do you have to grab it with pliers and just jerk it out? What about lube? Will grease do a 'number' on the plastic? Should folks be using cartriges that use a steel cup on the non-drive side?

TO11MTM

Grease shouldnt hurt most plastics... Ideally there WOULD be a steel cup but plastic is cheaper, and does have some other advantages (Namely, no corrosion...)

Funny story, actually. My Schwinn Suburban conversion included using a American->Euro bb so I could use cotterless cranks. Unfortunately, the Conversion kit's width was a bit over 68mm (About 71 or so...) I tried using one of the plastic cups, without much luck, it wouldn't thread in far enough because of the non-threaded 'shoulder' at the end of the cup.

Well, stupid me, I tried to force it in hopes the aluminum would cut the thread on the plastic. Nope, torqued the thing too hard and the cup cracked....

Well, to make a long story short, I used careful application of heat and melted some 'flats' in the cup to use a spanner...

HillRider

Yeah, I know it's not a "cup" in the formal sense but that's what everyone calls it.

HillRider

The trick to protecting the plastic "cups" is to not torque them too hard on installation and to remove the drive side cartridge first during an overhaul. Grease doesn't bother them.

They can be a real pain if they break during removal. Getting out the remnants requires a hacksaw blade, great care and copious profanity. Trust me on this, I'm the voice of experience.

Coyote!

>>> copious profanity. Trust me on this, I'm the voice of experience.

I will trust you on this one and since I can lay down a Barrage of Scatological Blasphemy** that will drop a Cape Buffalo at 100 yards, I think I have that covered.

** - A gift from my maternal grandmother and her German ancestors.

Kdarmy

Update:

Good news, stopped off at the LBS after work and they were able to fix it while I waited, only took about 10min.

They replaced it with a metal one, which I believe should hold up much better than the plastic style.

I took a look at the one which was removed and sure enough, it was split totally in half. With it being totally split the way it was I had the chance to bend it around a bit and see for myself just how ridgid it was. To my surprise, it wasn't...very easy to bend and if I had tried I could have snapped it completley apart.

This was the last plastic style BB cup I'll ever have installed in one of my bikes.

dafydd

all they do is support the BB on the non driveside, they don't have to be particularly rugged for the application. i've heard that shimano went to plastic to reduce bb creak, athough i'm sure cost savings were a factor as well.

i was just browsing through Bicycle! A Repair & Maintenance Manifesto (Sam Tracy), and he points out the fact that cartridge BBs are a lot more likely to seize in the shell, because nothing ever gets adjusted on them. Something i never thought about before, but in reflecting i realize i've had very few loose-ball bb cup that wouldn't come out with a normal shop tool (var, stein, BFW), whereas i've had countless occasions where i've had to use 4' breaker bars to remove seized cartridge bbs.

i guess what i'm trying to say is that steel cup may double the aspirin you might be needing down the road.

Kdarmy

Well there is an update to this post here:
https://www.bikeforums.net/bicycle-mechanics/321777-bb-problem-lbs.html

Tomorrow I go back to the LBS and will request that a new BB etc. be installed, plastic cup at this point would be fine, I just want it repaired and with the correct parts. This will be my third trip in for BB problems in the past month, I bought this bike new on 6-16-07...and I'm getting just a little tired of it.

Keith