Bottom bracket query

i have a raleigh zenith, i've almost finished getting all the parts for the build. but, what is stopping me is that the width of the bb shell appears to be 70mm.
i don't understand what i'm going to have to do to find a bottom bracket which will be the right size and also the right threading...
is it okay to use a 68mm bottom bracket and say +4mm on the spindle?

Are you sure it isn't Raleigh threading?

The width of the bottom bracket shell is also an indication. Standard British (24 tpi) bottom bracket shells are 68 mm wide, give or take a mm. Raleigh 26 tpi shells are generally 71 or 76 mm wide.

http://www.sheldonbrown.com/raleigh26.html

italian bb shells are the only ones that are 70mm wide.

if not, then i would have thought you could use a spacer like you can for some 73 and 68 mm bb's.

Shell width doesn't tell you everything. I have a 1963 Carlton frame that is British threaded (24tpi, not 26tpi) and the width is 70mm also. Yes, you can use a standard 68mm BB, it just means the left hand lock ring of a sealed BB doesn't screw in as far but still supports the BB.

Your chainline may be slightly different to what you expect, i.e. 1mm out, depending if the BB shell is 1mm wider than it should be on each side or if it is offset.

I have used a Sugino 103mm BB, Shimano 118mm BB (UN54?) and a BB from a Fuji Track all in his frame and all have worked fine.

Thanks for the help guys. I'm going to take it to my lbs in the next couple of days to get it looked at.
It MAY be raleigh threaded.
Is a threadless bottom bracket the option if this is the case?

I have just had a look at another old frame I have and that is also 70mm but has the raleigh 26tpi thread. Sometimes you just can't tell.

As Raleigh bought Carlton and gradually transitioned the Carltons to use progressively inferior parts on their lower end models throughout the '70s, I've heard it mentioned before that the wrong BB shells would sometimes get used on lower end models if there were none of the correct type left. They would thread the BB shell to suit the BB regardless of the shell width. I'm not sure where your Zenith lies in the range, or even if this was also the case with Raleighs. Best get someone to check it out.

i took it into my lbs and the guy measured it roughly. said i need either a 122mm or a 127mm axle.
said the shell was infact 70mm.
i told him about it maybe being raleigh threaded. but, he seemed convinced that an standard threaded bb would fit it without even looking or trying to fit something in there...
quoted £25 for the bb and £14 to fit it.
obviously i'd rather fit it myself...
i don't know what to do...
just buy a shimano un54? and see how that goes?
i may take the frame to my other lbs. they have always been a little more reliable.

Shell width doesn't tell you everything. I have a 1963 Carlton frame that is British threaded (24tpi, not 26tpi) and the width is 70mm also. Yes, you can use a standard 68mm BB, it just means the left hand lock ring of a sealed BB doesn't screw in as far but still supports the BB.

Your chainline may be slightly different to what you expect, i.e. 1mm out, depending if the BB shell is 1mm wider than it should be on each side or if it is offset.

I have used a Sugino 103mm BB, Shimano 118mm BB (UN54?) and a BB from a Fuji Track all in his frame and all have worked fine.

I also have a similar problem, with an old (and I mean old) Triumph. The shell appears to be 70mm.

I am wanting to use some Sugino RD Single Chainset on this frame. Does the above mean that I should therefore crack on with the recommended (Sugino) 68mm/103mm JIS bottom bracket?

Or should I look for a wider bottom bracket?... If so could anyone recommend anything please?

Cheers

Dave

you can use most options and fix the chainline with spacers/offset front chainring.