Removing a stuck Mavic 610 unthreaded bottom bracket...any ideas?

[sjcprojects]

I have a frame with a very stuck Mavic 610 BB, which is an unthreaded BB - the only threaded parts are the outer ends which stick outside the BB shell which the lockrings thread onto. Once the lockrings are off, it should be loose in the frame and just come out. Unsurprisingly given the state of the frame, instead the BB seems to have bonded itself rather nicely inside the BB shell.

I've put some penetrating oil (WD40 brand) down the seat tube, and given it a whack with a mallet from both sides, but no movement at all so far. I suppose I could try putting one of the threaded ends into a vice and try turning the frame to get some rotational force on it - which would almost certainly damage the threads (though saving the BB is unlikely anyway, I guess) - but I'm very doubtful it would give enough purchase to do that.

The problem is that there's no way of getting any sort of tool onto anything. I guess I'll have to resort to getting my local frame repair guy to heating it up to get it out, but I just wondered if anyone might have any other ideas...is it worth trying Plusgas or similar?

 

[Guinessisgoodforyou]

Have you tried turning the cups with a pin spanner?

 

[chickendrumsticks]

Have you tried turning the cups with a pin spanner?

They're easy to knock up if you don't have one:

The Viking Saga NOW SOLD

Re: It's going to look crap if I want to do that! However it came as 5 speed only, and I am happy to go with that. At the time (62) most models were just that - some just 4 speed actually. I think the single chain wheel won't look out of place. And there's only the one braze on for the shifter...

www.retrobike.co.uk

 

[sjcprojects]

You would think that might help, but the problem is that in fact using a pin spanner on those parts will only unscrew the outer cap (part 003 shown in this diagram), not the actual body of the BB.

 

[Takingabreak]

Can you fit both lockrings to the same side, tighten them against each other and then use one to try and turn the bottom bracket in the shell

 

[jim haseltine]

If you've got access to a chest freezer put the frame in there for a couple of days then pour hot water over the BB shell. With luck the expansion of the steel will break any corrosion between the BB unit and the shell. If no chest freezer you could try some plumbing freeze spray.

 

[bikeworkshop]

Those mavic bbs are quite a tight fit in the shell -
Looking at the corrosion
(those holes in a bb shell often cause a lot of trouble)
it seems you have that bimetallic alu/steel bond going on

Given you've got around 10 square inches of contact, I'm betting on the cat's chance in hell over twisting this one out.

Luckily the mavic bb is alloy, so unscrew the end caps, tap out axle and bearings, and then padsaw through the mavic bb cylinder.

I'd use an electric reciprocating saw to do most of it, and resort to the padsaw for the last bit so you can feel when you touch steel.

You might need to do 2 crosscuts.

Five minute job, mate.
Not.

 

[pigman]

If you've got access to a chest freezer put the frame in there for a couple of days then pour hot water over the BB shell. With luck the expansion of the steel will break any corrosion between the BB unit and the shell. If no chest freezer you could try some plumbing freeze spray.

As a bonus, during those two days you'll be feasting like a king to ensure nothing gets wasted

 

[kingbling]

if you can sit it in a tub/bowl of rust remover and leave it forever well a few days and check on progress

 

[sjcprojects]

Thanks for the thoughts, all. I'm pretty sure you're right @bikeworkshop - I can't really see much chance of getting it out with twisting. I have often questioned the wisdom of putting holes in the bottom of a BB shell, and this is definitely one of those times!

Luckily the frame is in a poor cosmetic state anyway, so I'm not bothered about the paint, at least. I think I'm leaning towards trying the pipe freezer spray/boiling water combination as a first try, and only resorting to more destructive means if necessary.

@kingbling – I know stuff like Evapo-Rust is pretty good stuff, but would it actually help break that alu/steel galvanic bond?