"SRAM has basically approached the situation with the same method as Shimano with a few exceptions since they entered the arena a little later. Early on, SRAM produced shifters that were cross compatible with the Shimano 1.7 ratio. This was called the SRAM (2:1) family of products. For the most part though, SRAM used their 1:1 actuation on 7/8/9-speed systems. Referencing the SRAM website, “Every unit of cable you pull moves the derailleur the same amount.”
Comparable to the Dyna-Sys release, with 10-speed systems both road and mountain, SRAM introduced Exact Actuation. The nice thing about the SRAM system is that all mountain 10-speed and road 10-speed are compatible, all using Exact Actuation. So you can use road shifters, with mountain derailleurs and vice versa—though it will be necessary to throw an inline barrel adjuster in the mix when using road shifters with mountain derailleurs.
I think the best Easter egg of all of this is that Exact Actuation remained for SRAM 22 road groups, meaning that if you wish to upgrade to SRAM 11-speed and you already have an 11-speed compatible freehub body. All you need is a new rear shifter, cassette, and chain. The cog pitch and derailleur ratio is the same on 10 and 11-speed road. So with a new shifter, your 10-speed derailleur turns into an 11-speed derailleur."
Texto parcial extraído de:
http://www.roadbikereview.com/reviews/tech-report-examining-drivetrain-compatibility/3
10v compatível com 11v? eis a questão...