Hello,

I have a Calfee Tetra Tandem purchased in 2009. The drivetrain is: FD-Shimano Ultegra 9 speed triple (53,39,28), RD-Shimano XTR(11-34). Shifting the triple has never been easy. It is basically pick the two chainrings you'd like to shift reliably and pray you can get into the other ring. I'd like to replace the triple with either a double (Di2 ?) or something like a Sram 1x. Last year I contacted Calfee and I am due to call them make after our season ends here in Massachusetts. As of our last conversation, aside from internal frame routing modifications there would be issue for me with the rear cassette. I'd need probably a 36 tooth or larger low end so we can get our butts over the hills here in Western Massachusetts. As you know, the Di2 road shifters won't shift a MTB rear derailleur. In summary, this solution would be very expensive. So I'm not sure this is the way to go. Now I just read some articles about Sram's 1x drivetrains with an 11 speed 10x42 and a wide range of front rings. Would this work? Has anyone tried this solution? Would it be less expensive? Thanks for any help.