Broken BB, what to do?

Sep 19, 2009
807
0
0
I've been working on a project bike for a few days doing a restoration of an old bike which was left abandoned for years in a garage.
I wanted to change the Bottom Bracket and as I applied force using the BB tool, the whole outer rim on the drive side (into which the splines go) just crumbled. That left me without a way to apply force to turn the BB to take it out and the BB stuck in the frame.
Is the frame trashed or is there something I (or the shop's mechanic) can do to save it?
 
Fourier said:
I've been working on a project bike for a few days doing a restoration of an old bike which was left abandoned for years in a garage.
I wanted to change the Bottom Bracket and as I applied force using the BB tool, the whole outer rim on the drive side (into which the splines go) just crumbled. That left me without a way to apply force to turn the BB to take it out and the BB stuck in the frame.
Is the frame trashed or is there something I (or the shop's mechanic) can do to save it?
What kind of BB and frame?

Pix?
 
Sep 19, 2009
807
0
0
It's an old mountain bike Cro-Moly frame with a square tapered BB. I'll try to get some pictures up.
On the drive side the metal of the BB was really deteriorated and the outer rim just broke but on the opposite side it was OK and I was able to torque it pretty good and turn it without problems.
 
So the non drive cup came out fine. Wow, i never saw the drive side break off like that. I am not sure how to proceed from there but soak the entire BB shell in ammonia, wrap a soaked rag around it and then plastic around that. Let set for a few days. Had good luck getting frozen parts out of bikes using that method. However you stll have to figure a way to turn the BB. Gotta think on that.
 
Sep 19, 2009
807
0
0
Here is a pic, it's horrible I think the frame is gone. You can still see a piece of metal left on the cup. I guess all those years exposed to the elements made the material brittle like uncooked pasta.

I wanted to turn the old Mountain Bike into a commuter for the winter:(
 
Aug 4, 2009
1,056
0
0
Dont forget it is left hand thread looks like you have been turning it the wrong way and tightening it.

Get an old screwdriver a big one and try to drift it loose with a hammer just tap it in the correct direction. see how you go.

Otherwise an oxy tourch in the correct hands will do the job.
Take the other side out that is right hand thread It may then fall apart.
looking closer at that pic you may be able to get the removal tool to bite try bolting it into place with a crank bolt so it dosnt slip.

I asume you dont want to re use the old bb. get a new one for Christmas
 
Not Gone

It's not gone forever.

It read like you have the other side out.

If so, pound out the spindle from the drive side. (of course) Those shells are pressed together, nothing too special so it will come out.

There's two ways to go now. The slow, steady route. Bathe in penetrating solvents for a week or so. Clean it up every 24 hours or so. Gently hammer the remaining shell as described in the last post. 7-10 days of bathing, get a heat gun and heat up the BB shell. The cup should come out with a little encouragement.

The quick and dirty route. You set up a metal hack saw in the shell and cut the offending cup. this gets tricky because if you aren't careful you can harm the shell. It doesn't have to be cut all the way through. Just most of the way through. Some pounding after that should crack the cup and thereafter free the cup from the frame. You will still need to loosen it like a regular bb. Done with some care, it will spin out, no harm to the bb.
 
Aug 4, 2009
1,056
0
0
From the photo it looks like you are turning it the wrong way it is left hand thread so clockwise to undo it .
Stick the removal tool on it and tighten it in place with a crank bolt very tight then try and move it .
you will then need to slack off the crank bolt as you turn the thread out.

if that dont work belt the spindle out and put a normal nut and bolt through the centre and as you tighten it with right hand thread the BB should come out. It may work.
 
Sep 19, 2009
807
0
0
Thanks for the tips, I'll try the crank bolt solution to see if the BB tool still bites. If it doesn't work I'll move on to more drastic measures.
If I'm able to get the old BB out by any means I'll definately get a new one, that was the plan all along. I want to use that bike during the winter so that the salt doesn't attack my other commuter and to give it a purpose in it's life beyond using up space in a garage.
The current BB has a kind of grainy feel but still goes so maybe it has some life in it as it is.
I'll keep you updated on the situation, Happy new year!
 
Mar 31, 2009
51
0
0
Looks like a standard Shimano UN BB with plastic cups - the plastic goes brittle over time and you have to resort to 'heavy tools' to get them out. Two options are to either push/press it out or simply support the BB shell and hit the end of the spindle with a 4lb club hammer. Alternatively, apply heat - it will soften and resort to a lesser brute force
 
Dec 28, 2010
17
0
0
Yes as Monty said that's one of those nasty plastic cups by the picture , I remember an afternoon spent removing a dearest comrade plastic cupped bottom bracket which had only been in one winter..horrible...persevere if the frame's got some sentimental value but remember the value of the bike is in the parts ...the Chinese can knock up an mtb frame for about 50$ nowadays
 

ASK THE COMMUNITY

TRENDING THREADS