Not work on other cranks is what Sram's marketing department will tell you. I am running a force crankset with praxis classic rings 53/39T. You set high limit and then low limit and it shifts from point a to point b. No chainrub in any combo including small/small and big/big with my ultegra 6700 12-23.
Ok, thanks, interesting. I'm running Specialized carbon cranks, with Red 50/34t rings. Have installed a DA7800 front mech, but would rather run the full kit, and not have to spring for the cranks as I don't need them.
Guy's I'm not guessing at this or asking SRAM... I have a new front mech on an old group set and it just plain works better.
I think Velonews covered most of the combinations and they also found that putting the 2012 Front der on the old SRAM group simply works quite a bit better.
The steel cage Force is a slight improvement, The 2012 RED is a substantial one, but I wouldnt change from the steel just to change... Frankly, any bitching about the steel one is mostly hot air. It works well. The Ti ones worked OK, but when you get the new one it's simply bang on.
That said, the entire new 2012 group is not only a breeze to set up, the whole thing works extremely well.