Which bottom bracket do I need? I don't know how to measure correctly.

[Brand X]

I read a blog post explaining how a 24tpi BB with plastic threads can be force-fitted to the frame of a Raleigh Twenty (26tpi threads), but I'm not at all sure what the correct size would be. Link to blog: http://www.rhizomes.squat.net/twenty.html

Measuring the bottom of the frame (the hole the BB goes into) it's about 77.5mm across, and the length of the old cotter-pin axle is about 142mm. The "FAG" bottom brackets recommended are sold at this website, but I really don't know which if any would be a correct fit.
http://en.hollandbikeshop.com/fag/
http://en.hollandbikeshop.com/fag/

 

[Brand X]

I also found this on eBay, it's some sort of converter. But would it be too short? It's only 130mm.
http://www.ebay.co.uk/itm/130mm-RAL...173973?hash=item58df854055:g:IcoAAOSwqfNXjisl

edit* Wait a sec.. I just found this: https://www.sjscycles.co.uk/bottom-brackets/cotterless-axle-7r-134mm/

I don't know if it's any use, but SJS are just round the corner and it's only 5 quid.

 

[simon.r]

I can't answer your question, but I'd be amazed if SJS couldn't as they seem to be the sole UK stockist of all sorts of weird and wonderful bicycle bits.

I'd pop in with your bike and have a chat with them.

 

[mjr]

If SJS don't know, I'd bet one of those BB cartridges intended for frames with trashed threads (where the two parts tighten against each other and the shell edges) would be a better bet than forcing the wrong thread in.

But does it really take a cartridge? I'd be expecting a loose axle like that7r (maybe not that exact size - the old one might have code or numbers marked on it, else I think Sheldon Brown tells you how to measure them) and I am fairly sure that Bhogal still make the cups with Raleigh thread.

 

[mjr]

I also found this on eBay, it's some sort of converter. But would it be too short? It's only 130mm.
http://www.ebay.co.uk/itm/130mm-RAL...173973?hash=item58df854055:g:IcoAAOSwqfNXjisl

Yes, sounds like the axle would be too short, intended for a 68mm shell. The cups would probably be OK but £11 would be a high price for some cups and caged balls.

 

[midlife]

I guess it's a 76 mm bottom bracket shell? Are you trying to fit in a new square taper bottom bracket?

Shaun

 

[Brand X]

I guess it's a 76 mm bottom bracket shell? Are you trying to fit in a new square taper bottom bracket?

Shaun

I want to fit modern cranks and a modern chain-ring, so it's a case of just doing whatever works. The easiest option - I think - is to buy a special 26tpi bottom bracket from Phil Wood & Co, but it's $56 for the cups - plus shipping and 20% import duty, and I would have to buy the special tool to fit it, which is $72, and a Phil Wood & Co BB cartridge which I can't find the price of.. probably adds up to way too much.

The cheapest option I've learned about is to saw 4mm off of the ends of the bottom bracket shell (I think that's what it's called) but if I get it wrong I've buggered-up the frame. Getting it done professionally would be in the region of £60 - £90, which is a lot for a frame worth about £10.

 

[Brand X]

I can't answer your question, but I'd be amazed if SJS couldn't as they seem to be the sole UK stockist of all sorts of weird and wonderful bicycle bits.

I'd pop in with your bike and have a chat with them.

Thanks Simon. Yes, I'll go and ask them on Monday. Fingers crossed.

 

[Smokin Joe]

I read a blog post explaining how a 24tpi BB with plastic threads can be force-fitted to the frame of a Raleigh Twenty (26tpi threads),

Fitting it will be one thing, removing it again might be something else.

 

[midlife]

Yep, the Raleigh 20 came with a huge bottom bracket shell length if memory serves. So lots of work arounds won't fit. For a frame worh a tenner I'd be tempted to get some material machined off the faces of the BB shell and fit a threadless BB like this....

http://www.freemanscycles.co.uk/bicycle-parts/acor-threadless-bottom-bracket-unit.html

Shaun

 

[raleighnut]

I want to fit modern cranks and a modern chain-ring, so it's a case of just doing whatever works. The easiest option - I think - is to buy a special 26tpi bottom bracket from Phil Wood & Co, but it's $56 for the cups - plus shipping and 20% import duty, and I would have to buy the special tool to fit it, which is $72, and a Phil Wood & Co BB cartridge which I can't find the price of.. probably adds up to way too much.

The cheapest option I've learned about is to saw 4mm off of the ends of the bottom bracket shell (I think that's what it's called) but if I get it wrong I've buggered-up the frame. Getting it done professionally would be in the region of £60 - £90, which is a lot for a frame worth about £10.

Unless you plan on altering the gearing I'd stick with the cottered crank, if you still have the undamaged shaft (can't remember how you got the stuck cotterpins out)

Mind you most people don't know how to install them (let alone get em out) cos the tool required is a 2lb engineers hammer (you knock em home then snug the nut up, a 2nd whack and then tighten the nut fully to stop the pin falling out. )

 

[Brand X]

Yep, the Raleigh 20 came with a huge bottom bracket shell length if memory serves. So lots of work arounds won't fit. For a frame worh a tenner I'd be tempted to get some material machined off the faces of the BB shell and fit a threadless BB like this....

http://www.freemanscycles.co.uk/bicycle-parts/acor-threadless-bottom-bracket-unit.html

Shaun

It's too expensive to get the BB shell properly machined, but I am tempted to have a go with a hacksaw. I'd have to figure out a way to cut dead-straight though; maybe by screwing a cup or something down into the threads to act as a guide. I did have a thought of putting a jubilee band around the shell to saw against, but there's no chance; it's only a few mm's of clearance.

I shall ask SJS Cycles before I start bodging.

 

[mjr]

Isn't the simplest just to replace the cottered axle with a square taper one of the same lengths, using the existing cups or getting Raleigh thread replacements? Or am I overlooking something?

I'm pretty sure most BB axle sizes are still available.

 

[raleighnut]

Isn't the simplest just to replace the cottered axle with a square taper one of the same lengths, using the existing cups or getting Raleigh thread replacements? Or am I overlooking something?

I'm pretty sure most BB axle sizes are still available.

If the bottom bracket is 77mm wide there won't be a shaft long enough between bearing faces to fit that width BB but sawing it down by 4.5 mill each side is going to be extremely difficult.

 

[midlife]

Isn't the simplest just to replace the cottered axle with a square taper one of the same lengths, using the existing cups or getting Raleigh thread replacements? Or am I overlooking something?

I'm pretty sure most BB axle sizes are still available.

Tricky thing about that is the width of the Raleigh 20 BB shell.... normal shells are 68 mm across but from memory the Raleigh 20 is 76mm so normal square taper axles don't fit. There are "Raleigh" BB square taper axles but they are usually for a 71 mm. BB shell so too small.

Here's a Raleigh square taper...


http://www.freemanscycles.co.uk/bicycle-parts/raleigh-cotterless-bottom-bracket-axles.html

Too small

Shaun