masi61

Does anyone know if Shimano triple crankset series such as Ultegra 6503/6603/6703 and Dura Ace 7703/7803 differ in any meaningful way with respect to which front derailleur and which triple STI front shifter they are paired with?

Just curious because I think I detected a change in trim positions when I swapped out my Ultegra 6603 triple crank for a Dura Ace Triple crank. I want to say that the Dura Ace triple rings seem to be spaced closer together making me have to trim more creatively to eliminate chain rub. Also, the Dura Ace starts to cross chain sooner causing me to no not be able to use a few of the small/small combos (not the most extreme ones) that worked OK on the Ultegra 6603 triple crank.

In the same vein - is there any subtle ramping difference between the Ultegra 6603 front derailleur with the Dura Ace 7803 front derailleur. I mean they are both designed for 3 x 10 systems.

le mans

I wanted to use a FD on a hybrid coz it just changes sweet, it was off a triple crank bike but i found it wasn't compatible for a narrower spacing triple crank {from memory}. Not in the same class or level components as yours but going off that not all FDs designed for triple cranks will work on all triple cranks

Andrew R Stewart 

Shimano's ring spacing and their ft der cable pull ratio differences between their road and MtB lines is well known. Within the each there have been subtle differences, generally between double/triple siblings of the same cog count and design vintage. Of course with any front set up cage/ring orientation and cable tensions have a big input too. Then add any front chainline shift (between swapped out cranksets) and ring teeth count differences and yes, there's no surprise that some minor performance change is the result.

We see this kind of thing often enough at the shop. A drivetrain component needs replacing and the customer complains that they now have chain rub where they didn't before. Sometimes even with the knowledge of trim functions (sadly many didn't know about ft shifter trim at all). Shimano has done a really good job at designing SYSTEMS that are rather dependent on each part's being system specific. Performance can change when parts wear out and get replaced with what's available at that point in time. This is one reason why indexed front shifting isn't the holy grail that many wish it was. Andy

dsbrantjr

Were they otherwise identical, like chainring teeth, etc? Same chain?

masi61

Same chain. I’m pretty sure the chainring teeth are the same @ 30/39/53.