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HELP! - Bizarre Stubborn MBK Bottom Bracket

chrubblechrubble Posts: 11
edited June 2014 in Workshop

I'm desperately in need of help with a bizarre bottom bracket that I have been trying to dismantle on an 80's(?) MBK Mistral.

I took off the octagonal lock rings and the drive side cup was unscrewable by hand, but I cannot for the life of me work out how to get the other 'domed' cup off. It seems to be connected to or part of a sleeve on the drive side (which the drive side cup screwed in to) and has no visible purchase holes/flats etc to enable me to grip and unscrew it. The axle appears to be permanently connected to it due to the the wider splays on either side of the dome.

Please see the pictures below for more detail. It is beyond me - I have never seen a BB like it - And I don't really want to go to the expense of having it ground out.

Both lock rings were removed anti-clockwise and all threads seem to run in that direction. I've had a plumbers wrench on the threaded part of the dome and tried to shift in both directions but there is insufficient purchase to budge the thing.

Left hand side protruding 'dome'

Drive side threaded sleeve

Lockrings and cup (with some of the bearings that didn't escape under the cooker)

My diagram of what I consider the construction to be when installed.

Please help me - before I try and chew the damn thing off. :? J


  • explosifpeteexplosifpete Posts: 1,327
    Could you not hit the drive side with a hammer to romove it the just maybe there will be notches in the rear of the threaded sleve?

    Good luck and i've never seen one like this before either
  • nicklousenicklouse Posts: 50,675 Lives Here
    looks like it is a bb for a cup that has stripped it threads?

    as above a hammer might help. maybe some plus gas as well.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • maddog 2maddog 2 Posts: 8,114

    not seen anything like it. I'd be tempted to angle grind some flat sections on the domed part, and try and get a big adjustable on it. It must unscrew out somehow.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • explosifpeteexplosifpete Posts: 1,327
    nicklouse wrote:
    looks like it is a bb for a cup that has stripped it threads?.

    I think you could be right
  • Sorry to resurrect the thread but did you have any luck with this?

    The LBS has an old MBK Mistral for sale and I fancy a summer project. It's £85 which feels quite a lot but it has two newish, decent tyres which I suppose saves me £30-£40 bringing the effective price down to a more reasonable level. It rides okay but it is 20-30 years old so might need a few bits repairing, replacing or simply tidying up and I don't want to be stuffed by an old BB that is difficult to remove and even more difficult to replace.*



    * I've read that these old French frames have a different BB standard to other bikes.
    Never be tempted to race against a Barclays Cycle Hire bike. If you do, there are only two outcomes. Of these, by far the better is that you now have the scalp of a Boris Bike.
  • tig66tig66 Posts: 1
    hey im sure you have worked it out by now but a hammer and a piece of wood works well. i broke mine some years ago! finally got round to rebuilding the thing now and i cant for the life of me find a replacement. anyone have an idea cause im stuck.
  • Hi all. I've got the same MBK bike and the same stubborn fixed cup on the bottom bracket. I tried the Sheldon Cooper website and made the make shift fixed cup remover tool (with bolts, spacers and nuts). I couldn't move the fixed cup, not even a bit. tig66 I don't understand what you mean by using a piece of wood and a hammer. Has anyone had any luck on this?
  • Hi there. I know I'm pretty late to the party here but I'm the middle of *trying* to remove the BB of my 80's MBK Triathlete. The thing is completely stuck in there and no bike shop will touch it. My main problem is that I can't get the non-driveside lockring off (nut edges are completely rounded). So the lock ring on the 'dome' side is stuck.

    What I'm trying to figure out is if the non-drive lockring is threaded on the inside or outside or both? I can't tell by the picture above so I was wondering/hoping if anyone out there could shine some much needed light on my situation.

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