I'm working on this Peugeot mixte. I have fitted a very nice Sugino road triple (74/110 BCD) with 30-40-50 chain rings. I don't know the spindle length in the bottom bracket, but I've converted it from the factory cottered spindle. The bottom bracket cups tighten down nicely on this spindle and preload is set appropriately. I like how closely the crankset snugs up to the frame, but I think my chainline (distance from rings to seat tube) is too small, and I'd like clarification/guidance before I change any parts. I have visited Sheldon Brown's website on chainline, and I definitely have less chainline than he notes there. I am measuring about 35mm in the small ring (picture 1 below) and about 40mm in the middle ring (picture 2 below). Sheldon Brown sez I should have 45 from the middle ring, with a road triple.

My issue is the very old (and cheap) Sun-Bow derailer will not move the chain to the small ring. It will bind on itself before moving far enough left (picture 3 below). This seems consistent to me with a chainline measurement that's too small. It appears that I will have to replace at least one of my current pieces of equipment (derailer, crankset, spindle).

My question: is any nicer or more modern derailer going to move far enough left to work on a ring with a 35mm chainline, or am I going to have to switch to a longer spindle to move the crankset out a little bit? I want to be able to use the small and middle ring on this crankset, and swap the large ring for a chain guard (either find one or make one myself out of another chain ring), and I like the 30-40 small-middle size for this bike so priority #1 , if I can, is keeping the current crankset. If I can just swap the derailer for a more modern one, that would be my desired move, but I'm hoping to hear from those more experienced to know if that's just a dead-end road due to my current chainline.

Thanks in advance for ideas and comments.

pug_cl_1 by jnjadcock, on Flickr

pug_cl_2 by jnjadcock, on Flickr

pug_cl_3 by jnjadcock, on Flickr