Bottom bracket question

[Ke1th]

Hi,does anyone know if my carlton cobra circa 1970 will accept a modern square taper bottom bracket?

[Eyebrox]

What was in it? Check the markings and/or dimensions of the bb coming out and match these with the units advertised online.

[philvantwo]

Mr Brucey will know!

[Ke1th]

It has the original cottered crankset with loose bearing bb.The bottom bracket needs work now and I was hoping to replace the lot and avoid the hassle of removing cotters again.

[Mike Sales]

Should be fine. You will need a new chainset of course, and the new BB must be the length to suit.

[Ke1th]

Should be fine. You will need a new chainset of course, and the new BB must be the length to suit.

that's what I like to hear.

[fastpedaller]

Is it possibly a 26TPI threaded bb? Brucey will know?

[Mike Sales]

Is it possibly a 26TPI threaded bb? Brucey will know?

Very unlikely. Only older Raleighs were 26 tpi.

[cycleruk]

Hi,does anyone know if my carlton cobra circa 1970 will accept a modern square taper bottom bracket?

More than likely. Unless manufactured for something special then probably a standard English BB.
A couple of things to decide - chain line and axle length.
Axle length may or may-not be equidistant either side of the BB. Some can have more axle on one side than the other.
Also, dependant on cranks, there are a couple of square taper angles which have to be considered.
Have a look at Sheldon's website for BBs.
https://www.sheldonbrown.com/gloss_bo-z.html#bottom

I have, a long time ago, done exactly as you want with no real issues.

[Mike Sales]

Is it possibly a 26TPI threaded bb? Brucey will know?

24 tpi threaded BB shells measure 68 mm, face to face. If it is closer to 71 mm.it will be 26 tpi.

[Ke1th]

Is it possibly a 26TPI threaded bb? Brucey will know?

24 tpi threaded BB shells measure 68 mm, face to face. If it is closer to 71 mm.it will be 26 tpi.

Which is more favourable?

[Mike Sales]

Is it possibly a 26TPI threaded bb? Brucey will know?

24 tpi threaded BB shells measure 68 mm, face to face. If it is closer to 71 mm.it will be 26 tpi.

Which is more favourable?

26 tpi cups are hard to get hold of and there is limited choice, even if you can find them. Raleigh stopped using them some decades ago, and all remotely modern bikes on the British market are 24 tpi.

[Ke1th]

Thanks,I'll measure it tomorrow.

[fastpedaller]

My query re 26TPI was because of the Carlton/Raleigh connections. If it's 24TPI then a modern cartridge should fit, If a tube (or 2?) are a little long inside the shell, a carefully applied file usually sorts it
It's easy to check if 24TPI by carefully placing a 24TPI hacksaw blade in position and seeing if it 'fits' the thread!

[Mike Sales]

My query re 26TPI was because of the Carlton/Raleigh connections. If it's 24TPI then a modern cartridge should fit, If a tube (or 2?) are a little long inside the shell, a carefully applied file usually sorts it
It's easy to check if 24TPI by carefully placing a 24TPI hacksaw blade in position and seeing if it 'fits' the thread!

Another way to distinguish old Raleighs is that the headset is also 26tpi and a modern race will not thread on very far.
In fact, I can't remember seeing a Raleigh ATB in the old threading.