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my name is Alex and I’m new here. I’m a bit of an amateur but I’ve decided to attempt the modernization of an old French Liberia racer from 1978. The aim is to create a bike I can use as a daily commuter bike.

But I’m struggling with the removal of the square tapered, Swiss-threaded bottom-bracket: enter image description here

The variable cup came off easily enough on the non-driver side. But the fixed cup on the driver side is not only really stuck, it also has a non-standard size! There are two flat edges for an open wrench/spanner with a 37 mm gap between the flats. Unfortunately, I do not own a 37 mm wrench, so I tried to loosen the cup using an adjustable wrench and failed miserably! The amount of torque needed was just too great and the wrench kept slipping off due to a combination of the unavoidable amount of ‘play’ in the adjustable wrench setting and the fact that the fixed cup is not very wide (about 2.5 mm I think), which certainly does not help.

One helpful post on stuck bottom-brackets suggested using a large vice to clamp the cup and the frame should then provide enough leverage. Also, it might be helpful to use some penetrating oil from the inside of the BB and to give it some time to seep into the threads. Right now, sadly I don’t have either of those in my toolkit, but I have a feeling this might change soon!

So, I’m thinking I might need to use a regular open-ended wrench of 37 mm width, but these seem to be impossible to purchase anywhere, given the non-standard size. I’m also thinking that, to avoid slippage, the wrench should ideally be kept in position while torque is exerted. Apparently, there is a device to help do this being sold by Park Tool, but it is not cheap and may be too soft for the task as it's made of aluminium, according to the reviews at least. I guess making some sort of home-made retainer using a couple of metal plates held in position using a threaded bolt / rod and two nuts might be the way to go – not sure yet.

So anyway, this task seems to be a bit of a tough one! Not sure if the bench vice option is preferable or if there are other solutions out there - ideas anyone? Any feedback you folks might have on how to best approach this would be highly appreciated.

Best Regards, Alex in Hamburg

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    You've probably tried the following, but just to check: when I want an adjustable wrench to grip a nut very tightly and not back off under high torque, I put it on the nut, tighten the wrench adjustment, and then while continuing to apply force to the wrench tightener, as if trying to tighten it further, I wiggle the wrench back and forth about the axis of the nut I'm trying to remove. Often it will tighten a little further from doing this, to the point where it won't back off when you then apply high torque to the wrench handle.
    – SSilk
    Commented Aug 9, 2023 at 11:15
  • What types of penetrating oil do you have available? You can also try heating the bottom bracket shell with a blow dryer - try to heat only the frame itself so there's a temperature difference between the frame and the bottom bracket threads. Just be really careful if you use the blow dryer after applying penetrating oil - the blow dryer shouldn't be hot enough to ignite the oil, but... Commented Aug 9, 2023 at 11:47
  • A local bike shop might be prepared to just undo this for you in their vice for a token payment (or even for free) and without demanding that you spend on other goods or services. And so might any other business that has a vice: car mechanic, furniture fitter etc. I'm ambitious about doing my own repairs but my pride doesn't hurt too much if I ask for help in such situations.
    – pateksan
    Commented Aug 9, 2023 at 12:29
  • 37 mm wrenches don't seem too hard to find, at least not for me from where I am in the US. Maybe you'll be able to find one: google.com/search?q=37+mm+wrench Commented Aug 9, 2023 at 22:22
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    There is a type of adjustable spanner that also features a locking vice grip that can absolutely help you. Also are you 100percent sure it's a swiss thread? Just checking!
    – Noise
    Commented Aug 10, 2023 at 17:19

2 Answers 2

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There's a solution that is pretty likely to work: go to the "Fixed Cup Tools" heading on this page, which describes how to make and use this:

enter image description here

This can be harmful to the cup, although not as much as one might think because typically you can pick out a washer where you're not actually touching it against the bearing contact surface.

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    Linking to Sheldon Brown should earn double for every +1 you get. :-) Commented Aug 9, 2023 at 22:28
  • Concur - a Sakae BB is worth making an effort to save if possible. They're not trash unless they're worn completely out.
    – Criggie
    Commented Aug 10, 2023 at 2:01
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Thank you all so much for your fantastic tips!! After much toil, this story now has a happy ending!

First of all, after reading all your helpful posts, I took a trip to my local bike shop - they were absolutely amazing and did not charge any money for their efforts. Unfortunately, in the end they were not able to remove the fixed cup. Their first attempt was to use a high quality 37 mm wrench. When this failed, they tried the vice trick, where the flats were placed inside a vice and the bicycle was turned. Two strong men were unable to remove that damn cup!

This left Sheldon Brown’s special tool construct as a final attempt as kindly suggested by Nathan. I was a little skeptical whether this would work. Never-the-less, I took down some measurements of the bottom bracket and purchased some appropriately sized parts (my local DIY stores did not stock the correct sizes, so these all had to be ordered online). My assembled ‘tool’ looked like this:

enter image description here

For anyone else that might be interested, it comprised an M14 x 40mm hexagon head bolt with thread up to head and a corresponding M14 hexagon nut. To clamp the outside of the cup, I used a standard M14 washer with a large outer diameter. To clamp the inside, I could not find any M14 washers small enough, so I used some B14 Form B split lock-washers. In my case, I needed to use 8 – any less and the bolt head would have not been accessible with my socket wrench.

Before starting this final attempt, I sprayed the interface between the cup and frame with plenty of WD40 and let this soak in for a couple of hours. Then I got out the hairdryer and heated the outside frame, making sure that no hot air got inside the shell (I wanted the heat from the hairdryer to expand the shell and not the cup).

Using a socket wrench and an open-ended spanner (22 mm), the first step was to tighten the nut/bolt tool around the cup - really tight. Then, the next step was to turn the nut on the driver side to loosen the cup. My first go did not budge it, and made me realize I need to tighten the nut/bolt even further, which I then did. My second go again did not manage to budge the thing. With all my strength, I tightened the nut/bolt as hard as I could. Lo and behold that fixed cup started to move! The end result – a perfectly intact bottom bracket and shell.

The funny thing is, it turns out to be a FRENCH threaded bottom bracket after all and not SWISS one – how crazy is that!?

Anyway, all’s well that ends well, right? I hope this story might inspire others in a similar predicament not to give up 😊

enter image description here

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  • Good detail on the solution. Probably not a bad idea to chase the threads with the proper die for the thread. It may be tough to find that thread, but an old local bike shop may have that one lying around just waiting for your frame!
    – Ted Hohl
    Commented Sep 12, 2023 at 11:15

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