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

[Brand X]

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.

I read that there is a square-taper BB that is long enough, but nobody has a supply of them anymore, they're like hen's teeth.

 

[midlife]

Yep, that's the problem .

Have you tried on the specific Raleigh 20 website..



http://raleightwenty.m.webs.com/sit...2&fw_sig_site=48617018&fb_sig_network=fw#2303

Shaun

 

[Brand X]

I'm probably barking up the wrong tree, but perusing Google I found that there are "extra-wide" bottom bracket cartridges made for "fat bikes" (customs and cruisers) and for electric and motorized bicycles. Page: http://www.sickbikeparts.com/catalog/index.php?cPath=23&osCsid=8cpeh9ln0c673j4043l4ero0s4

I'm not sure what I'm looking at, but this one is for up to a 73mm frame and is 148mm long - which perhaps is too long (original cotter spindle being 142mm).

 

[raleighnut]

I'm probably barking up the wrong tree, but perusing Google I found that there are "extra-wide" bottom bracket cartridges made for "fat bikes" (customs and cruisers) and for electric and motorized bicycles. Page: http://www.sickbikeparts.com/catalog/index.php?cPath=23&osCsid=8cpeh9ln0c673j4043l4ero0s4

I'm not sure what I'm looking at, but this one is for up to a 73mm frame and is 148mm long - which perhaps is too long (original cotter spindle being 142mm).

Probably still won't be a long enough thread to fit a 77mm wide bottom bracket though.

 

[Brand X]

Probably still won't be a long enough thread to fit a 77mm wide bottom bracket though.

There's another one, but it's a whopping 83mm. http://www.sickbikeparts.com/catalo...ucts_id=189&osCsid=8cpeh9ln0c673j4043l4ero0s4

Uhhh.. and I just realized I'm being a flaming idiot again. Those are 24tpi threads and the cups are probably metal rather than plastic, and I hadn't even thought about what diameter they are. I really ought to stop typing after 11pm, my brain goes to sleep without telling me.

SJS. I will ask at SJS.

 

[tyred]

I'd think very carefully before taking a hacksaw to the bottom bracket shell. It needs to be cut accurately for length and also 100% straight or new bearings won't last very long. If you insist on doing this you don't necessarily need to pay a frame builder as any decent engineering shop should be able to do it. I like to do things myself where possible but this would be one job I'd definitely farm out to someone with the skills and tools to it accurately.

These things can be done but I don't see any point. The Raleigh chainwheel is a work of art, will outlast anything you can buy today and properly polished chrome chainsets look beautiful and properly installed cotterpins will work for thousands of miles. A lot of online "experts" say they don't work but they do in practice and people have cycled around the world on cottered chainsets. Proper installation is the key. They also will be easily removed if installed properly.

An R20 will always be a heavy bike no matter what you do and it is not a performance orientated machine so there is nothing to gain (IMO) from changing it to square taper.

 

[mjr]

I read that there is a square-taper BB that is long enough, but nobody has a supply of them anymore, they're like hen's teeth.

Yep. Just tried and I can't find any any more.

Here's Sheldon's page BTW http://sheldonbrown.com/raleigh-twenty.html#bottom

 

[Brand X]

I'd think very carefully before taking a hacksaw to the bottom bracket shell. It needs to be cut accurately for length and also 100% straight or new bearings won't last very long. If you insist on doing this you don't necessarily need to pay a frame builder as any decent engineering shop should be able to do it. I like to do things myself where possible but this would be one job I'd definitely farm out to someone with the skills and tools to it accurately.

These things can be done but I don't see any point. The Raleigh chainwheel is a work of art, will outlast anything you can buy today and properly polished chrome chainsets look beautiful and properly installed cotterpins will work for thousands of miles. A lot of online "experts" say they don't work but they do in practice and people have cycled around the world on cottered chainsets. Proper installation is the key. They also will be easily removed if installed properly.

An R20 will always be a heavy bike no matter what you do and it is not a performance orientated machine so there is nothing to gain (IMO) from changing it to square taper.

My plan is to ditch everything except the frame and possibly keep the 3-speed hub. But if I can't keep things to a sensible budget I'll keep the bike more or less as is. I do have a Dawes Kingpin too; I have no idea if it has the same 26tpi thread and super-wide BB as the Raleigh Twenty, they're basically the same bike (the Kingpin being a bit nicer) but they're not identical. I'll take a look tomorrow if I can dodge between the raindrops.

(edit) Looks like a 70mm BB shell. I'll have to measure it properly with the cranks off, but it looks promising.

 

[midlife]

Dawes were never part of the Raleigh empire and AFAIK has normal components. Nice bike the Kingpin
Shaun

 

[tyred]

Dawes will be 24 TPI

 

[Brand X]

Dawes will be 24 TPI

That's what I wanted to hear!
Looks like I'll be keeping the Raleigh Twenty in standard trim and tinkering with the Dawes Kingpin instead.