Ah, my first post. I hope not to offend, but would like an answer to this question as well. Although I have rather made up my mind on this one. So if anyone has tried this please speak now.
Having just bought the last 10 speed groupset avalible at pre 2007 prices I am awaiting the arrival of a chorus package with 10s ST chainset, Square taper n' all.
Looking to change the c/set to an Ultra torque 11 speed as they are far more available.
Here goes. 11s uses a narrower chain (as remarked previously). This is to allow for the closer sprockets on the cassette. While only a fraction of a mm, never the less, a significant amount for an indexed system that has been crammed into a set space, moreso over the past few years. (8 and 9 speed freehubs are the same size, the increase was made up from 7 speed systems. at which time the dropouts of road bikes were seperated by a further 5mm [ reference required ] and the hub witdth increased accordingly). All well and good to say don't run a 10 speed chain on an 11 speed system for this reason.
However at the front end (chainset) it is a different matter. Campag does not use indexed front shifting (they utilise a 'micro ratchet' etc.) therefor allowing a raft of adjustment to both get the chain onto the correct ring and keep it there. This eliminates the problem of spacing between chainrings and the use of different speed systems or indeed double/tripple chainsets. What about the narrower chain. Yes it should not fit over the teeth of an older system (11 s chain on a 10/9/8 chainring) This I would think to be a problem (chain suck, split links, cracked rollers, ...) But surley the wider chain will breaze onto the newer chainrings. Not so loose as to be a problem of any kind. Unless the pitch of the chain is different (distance between the pins) it should work with the newer chainset without fault. The chainline is the same on the new systems as the old, so drive angles from chainrings to cassette are the same (ie chain won't be snagging bigger rings any more than the correct combination would). the 0.4 mm that the chain rings may
have been mover together is not going to make an apreciable difference to shifting between a 39/53 or 34/50 with a slightly wider chain. The chain still has to be pushed onto the ramps to make the shift/ pulled off the ring to make the drop.
I'll be sure to let you all know as soon as I have the kit.