Originally Posted by
davester
Also, if you have early Campy cranks on that bike, then the newer derailleurs with the CPSC-mandated lip on the front may not clear the crankarm. The year that the lip appeared Campy brought out a modified crankarm that is moved a few millimeters further to the right to avoid this problem. That said, I have an incompatible pre-/post-CPSC set on my bike and with careful adjustment I can get it to shift OK while maintaining less than 1 mm clearance to the crankarm. YMMV.
that's almost always an issue for me when i build a record bike. it's a balancing act between perfect chainring upshifting, trimming, and arm clearance. after five builds, i think i'm getting a little better at it.