or, what is the difference between ESP and Exact Actuation?
I've been dreaming of both converting my main ride to a 1x9 and being strong enough to rock the Front Range climbs without a granny years before SRAM debuted its 2x10 system. I've been fairly successful at avoiding shifting out of the middle, but that granny does occasionally pay its own way.
I went to a SRAM demo day a couple of months ago at Golden Bike Shop where they were demoing a bunch of brands of bikes all set up with XX and X.0 2x10 kit.
red=mt., blue = road?
I didn't feel much difference in the rear shifting, but absolutely loved how the front just slammed left and right into the two rings without blinking, under almost any load. I loved the decrease in ratio overlap and the loss of forbidden gear combinations. However, I just don't have the budget right now to pick up a new drivetrain.
I asked the SRAM rep what the minimum equipment change would be to go 2x10 from a 3x9 system that was a handful of years old. He told me that I needed it all: Both derailleurs, shifters, crank, chain, and cassette. Maybe it's my mistrust of authority, or maybe salespeople, but somehow I just don't think that the path the derailleurs travel can be that different. I want to believe that I can get away with keeping my old derailleurs and saving some money. (It's hard to even call it "save" if you don't have it to begin with!)
Years ago, I tried making my own stick shifter (not successfully, but I'm still working on it) for a cruiser. I took apart a Shimano shifter and was surprised that the teeth on the shifter weren't the same distance apart. I was excited to see that SRAM used a 1:1 shifting ratio. I'm still not sure exactly what that means, but assume that for every unit of cable pulled, the rear derailleur moves that same unit distance away from the cassette (perpendicular to the wheel axle).
SRAM image of Exact Actuation's 1:1 ratio
My 3x9 kit seems to be called E.S.P. by SRAM and claims a 1:1 ratio. The new 2x10 kit claims the same ratio, but seems to have dropped the E.S.P. and is now called Exact Actuation. Assuming the cable pull ratio has stayed the same, I should be able to use my old derailleurs to build up a new 2x10 bike, right? I just can't find anything on the internet about the difference between E.S.P. and Exact Actuation.
If both have the same cable pull to movement ratio, the only difference can be that the path the parallelogram travels, right? And that's assuming there even is a difference. Does anyone know? Can anyone help me figure this out?