Originally Posted by
caloso
My first generation 10-spd Red RD is toast. Any reason, other than a few grams, to get Red to replace it? Force or even Rival seems like a better option.
you have one of the titanium cage versions, then? if so, they can be flexy and yield to poor shifts; in that respect, the force one is actually better (performance-wise, at the expense of a few grams). however, if you never noticed problems maybe you can get away with using it on your setup.
Originally Posted by
spectastic
how much better is shifting under load on a di2 than a mechanical setup? or what's the difference?
significantly.
Originally Posted by
globecanvas
Much, much better. The motor pushes the cage an order of magnitude harder than your puny hands and levers and cables can. It can make for bad habits, because it doesn't punish you for shifting like an idiot.
di2 also exposes "flexy" chainrings due to the powerful shifts. i don't believe that mortals can tell any loss in power from one chainring to the next, but flexy chainrings can cause poor shifting and/or dropped chains (people more often blame the FD than the rings, IME).
the shimano rings tend to shift the best with di2 when i've done comparisons with all else equal (same bike, same drivetrain/FD/crank arms....only change was the rings). even solid rings (like the specialized ones) and reportedly stiffer "Sprinter" sram rings are not quite as good. there's a measure of subjectivity there, but it is noticeable if doing the comparison.