As above what size square taper BB do I need for an On One steel inbred? Its a few years old the frame, not sure if they’ve changed at any point?

Also any recommendations for which make/model?

Ta

Axle length is specific to your chainset.

However a standard 47.5mm chainline (which the Inbred is designed around) is normally achieved with a 113mm axle for a Middleburn chainset for example/.

If you mean shell width, then it’s 68mm.

The bike is only something cheap for the wife to occasionally use so I’ll probably go for something like this – Shimano M442 Square Taper Chainset – http://www.chainreactioncycles.com/Models.aspx?ModelID=46021

Id hazard a guess that you would be fine with anything between 110mm and 113mm:

http://sheldonbrown.com/bbsize.html

search for M440

Bb shell on my inbred is 73mm

M442 needs a 110mm BB-UN26(-E) for 47.5mm chainline according to this
Shimano Doc.

Bb shell on my inbred is 73mm

Are you sure? both of mine were 68 and the website still says 68.

As for the length, it depends entirely on the chainset, look it up in the manufacturers technical docs. I personally would run a 50mm chainline, there’s not much clearance between the chainset & chainstay so definitely wouldn’t run 47.5.

Thanks for all the replied guys. I’ll go with the 113 BB which will give me almost 50mm CL.