BB advice please

[taximan]

I am working on a Hugh porter frame which I have just had resprayed and want to keep it as original as possible therefore I intend to set it up as a ten speed. Before the respray I was using the bike with a triple chainring on the front and I intend to replace it with a double. Can anyone tell me what size bottom bracket bearing I need. The label on the old bearing is unreadable.

 

[Ajax Bay]

I can't tell you, but.
The triple was probably using a 122.5mm BB spindle (you can measure it). The double crankset will likely need one a little shorter, but.
The double should specify what length BB spindle it requires - the length of the old one doesn't matter.
For example the smart doubles that Spa Cycles sell for this sort of rebuild require a 110mm BB. YMMV.
HTH.

 

[taximan]

I have just checked the double chainwheel & its marked 110mm BDC. Is this what I am looking for?

 

[Ajax Bay]

No - that is the Bolt Centre Diameter (BCD) which describes the chain ring bolt hole positions.
Edit: Try finding the chainset on line and see if it specifies the BB spindle length.
Also for info: https://sheldonbrown.com/chainline.html

 

[taximan]

OK. thanks