Chainline with a Double Crank

I know that there has been many a thread about chainlines - I've been trawling them for days - but I can't find the info I'm looking for.

I know that you can buy single ring bolts for the chainring - I may just machine the existing ones down at work - but there just doesn't seem at the moment to be enough room. The smallest chainring has a chainline of 50mm c to c. I've got a set of Miche/Mavic wheels. The hubs are the Miche Primato track hubs single side which I believe have a 42mm chainline - I haven't measured them but that's the info I have gained from on here. So that leaves me 8mm out. I could make up a set of chainring spacers, but 8mm seems a bit excessive - besides which the chainring bolts probably aren't long enough. The frame is and old 80's Pug (Peugeot UK but French built) with a 67mm shell width. I believe the bottom bracket to be English threaded but I can't be 100% as I haven't taken it apart yet - the other bike isn't yet finished and this is my main transport.

So...can anyone give me any pointers? Has anyone else on here gone down this route? I'm looking to buy single cranks in the end, this is all just to tide me over. I have a feeling a new bottom bracket is in order anyway so may just get one 4mm shorter? This is all new to me and some help would be appreciated.

Cheers
Anthony

I used a 110mm BB on mine, with oldish Stronglight cranks.
Could you put the ring on the inside?

BRM I used a 110mm BB on mine, with oldish Stronglight cranks.
Could you put the ring on the inside?

this should work if they are matching ie JIS with JIS or ISO with ISO.

The industry standard chainline for a double road chainset puts the inner ring at 41mm and the outer at 46mm. This is supposed to be a standard (so front derailleurs and frame makers are all in tune) but in practise it can vary a bit. You can of course use different length spindles and chainring postioning/spacers to alter it a bit to suit.

50 mm sounds a bit much for a old pug road frame. That is the chain line for a middle of a mbt chain set.

Yes a new bottom bracket is required. Remember that a b.b is symmetric (well most are there are some out there that are not but rearly) so if you wish to move the chain line x mm you need a b.b which is 2x mm shorter / longer.

It is a weird one but the drive side crank is not standard. Its a reclaimed Shimano that may well be the wrong taper!! I think I have to strip it all down and have a good look.

Ahhh! this may be your problem

But Shimano is JIS and pugs are European so if diffrent would mean iso so as the late great Sheldon Brown said.

"if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length. "

So may be that is not your problem. (Unless you have a njs Shimano crank hence iso and then a jis b.b).

Ok. Sounds like I'm going to have to go out and get a locknut spanner ASAP and whip off the BB. Might even be worth heading to the LBS to see if they can match up the drive crank with a non-drive and then sort the chainline from there. Balls. Wanted to avoid the LBS but sometimes it can't be helped I suppose. Thanks for all of your help.