Removing a stuck bottom bracket

[GrahamGKD]

I am posting this on the off-chance it might be useful to someone else with the same problem…

I was asked to have a go at removing a stuck bottom bracket from a titanium frame.  The BB was a Miche square taper with alloy cups - the shoulder had been removed from the drive side cup to allow for better chain alignment, not that that makes any difference to removing it.

A LBS had already had a go at it, including trying an air impact wrench, and had stripped the extraction splines on both cups!  The owner was ready to write-off the bike so there wasn't much to lose.

I made a drill guide using a pillar drill to drill two accurate holes in an odd lump of metal I had knocking around.

2018-03-07 17.48.33 by Graham Dore, on Flickr

The large counterbored hole fits snuggly over the square taper of the BB spindle and the small one acts as a guide for a 6mm drill.

This allowed me to drill accurately into the BB shell with a hand held power drill without risk of touching the frame with the drill bit.  The red leather welders apron is to fend-off damage to the frame in the event of the drill breaking (which wasn’t necessary).



I tried one hole both sides and used the drill guide tool with a high tensile bolt inserted through it into the cup.  I tried to unscrew the cups by turning the drill guide with my monster stilsons – no chance – the bolt sheered both sides.

Having drilled all the way around both cups (turning and re-clamping the drill guide for each hole) I found a piece of tool steel which just fitted tightly through the guide hole on my drill guide.  I clamped this to the BB spindle and used it to scrape away the metal between the holes on one side, exposing the bearing.





I drove the innards of the BB out of the open cup with a lump hammer – it was very tight, so I tried to turn it with my monster stilsons in the hope it would unscrew the cup – it didn’t – the innards of the old BB shattered.



I removed the innards of the old BB completely and VERY CAREFULLY cut slits in the remains of both cups with a hacksaw.
After a bit more faffing, repeatedly sawing a bit and then using a punch, I managed to get both cups out without any damage to the frame.  Big sigh of relief.

[zigzag]

looks like a lot of work! well done for extending the frame's lifecycle

[Canardly]

What he said. Cups seem well greased.

[Brucey]

blame Miche for being daft enough to copy campag's crappy spline design; it is just not man enough for removing a BB that has been in for more than five minutes. Stupid idea.... the campag spline is guaranteed to fail at about 1/4 of the torque that a shimano BB spline will cheerfully accept.

I have several times had to remove similar BBs that were similarly stuck.  FWIW the aluminium cups are soft enough that you can attack them other ways, for example

- die grinder
- hole saw
- hammer and chisel

so as to expose the bearing unit enough to be able to muller it out. Depending on the BB, the centre part is between 27mm and 30mm diameter, so you need to make a hole in the cup of the corresponding size.

cheers

[Torslanda]

...and don't forget the inherent knobheadedness of using aluminium for the cups? I'm all for saving weight but that's just the wrong material for the spline size.

[GrahamGKD]

blame Miche for being daft enough to copy campag's crappy spline design; it is just not man enough for removing a BB that has been in for more than five minutes. Stupid idea.... the campag spline is guaranteed to fail at about 1/4 of the torque that a shimano BB spline will cheerfully accept.

I have several times had to remove similar BBs that were similarly stuck.  FWIW the aluminium cups are soft enough that you can attack them other ways, for example

- die grinder
- hole saw
- hammer and chisel

so as to expose the bearing unit enough to be able to muller it out. Depending on the BB, the centre part is between 27mm and 30mm diameter, so you need to make a hole in the cup of the corresponding size.

cheers

Agree about the spine but having seen the state of the threads I don't think any amount of rotational force would have got them out - I fear the frame would have collapsed first! Even after I had cut out a small section and slit the opposite side the cups were still hard enough to get free.

I do have die grinders and ordered some burrs to use with them with this job in mind, but in the end I opted for the method above because I was more confident of avoiding any damage to the frame that way.

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