Originally Posted by
glye
If you have the SRAM DualDrive, this has a combination shifter that shifts both the hub and the cassette. You'll need to find an 8/9 speed one, and since they're not made anymore
afaik you may have to look for it in the 2nd hand market or ebay. You don't need a special DualDrive derailer, but it must be an SRAM MTB derailer.
The original Birdy Blue with Sachs (prior to SRAM buyout, when it went 8sp) had a 7 Speed based dual drive with separate twist shifters both with standard shimano 7 sp pull ratio's. Any old shimano/sram compatible 7 speed Rear Mech and shifter will do the job. I had a pair of standard Sachs Waveys that did the job nicely with an M739 XT rear mech. Still have set in the Shed
afaik.
RandomHajile Im surprised the Dual Drive (if thats what it is) isn't low enough for you, with a 52T chain ring I could climb cliffs with it, I must have used that gear <10 times on 5+ years of London commutes. I wonder if the if you have a bigger than standard chain ring?