SRAM Red with XX cassette and XX rear derailer?
 

Has anyone ever successfully installed SRAM Red shifters, compact double cranks with SRAM Red front derailer, and SRAM XX cassette and XX rear derailer on a tandem? With good as a tandem shifting?
Well, I will if I get any warm fuzzies from the tandem geeks.
Thanks in advance.

I have been wondering about the SRAM XX group myself and am looking forward to learning other tandemist's experiences with SRAM XX. Thank!

Officially, it should work fine. For a far cheaper alternative that is designed to be used in this way, check out the new SRAM Apex group that will be available in a few months.

I am keeping my eye on this group, but it still appears as it is only compact and not available in a triple. Would be nice to have double-tap in a triple.

Would a disadvantage of a compact double be not smooth shifting with a wider ratio MTB cassette? You can have just as wide gearing, or wider, but the larger jumps between gears is an ok tradeoff on a tandem for me. I just really hate that triple. Am I missing something?

Yes, I too think it will work. The Apex rear derailleur and cassette seem to be promising options if you are on a budget.

I switched out our Tandem to SRAM Force a couple of years ago and have been riding it with no problems. I went from a triple to a double by giving up the big ring and replacing the 39T center to a 48T and keeping the 30T. I guess you can call it a Granny-Compact. That with the 11-28 cassette gives us all the gearing we would ever use around here plus more climbing gears if we will ever need it.

Many people who post in the Long Distance Cycling forum run a similar drivetrain setup, it's often referred to as a Super Compact. I run variations of it on a couple of my bikes, with a 46-28 plus 11-26 on my fast road bike. I wouldn't want to use it on the tandem though because the cadence jump between chainrings is HUGE and takes some skill to shift it smoothly by combining it with rear shifts at the right time and anticipating the jump; I think it would be very difficult to make that shift smoothly on a tandem. So, I wouldn't recommend it on a tandem (even though I love the setup on a single bike).

Good point. The small ring is never used around here. No long climbs, just bumps and rollers. I have only shifted the front to see if it works and that does not count as real world usage. I wonder if they make a 74BCD 34T ring. That would make the gap smaller. That with the new Apex or XX rear setup should be better.

TA make 74mm BCD rings in sizes up to 36 tooth, see this pdf from their website. However, anything bigger than 32 can be difficult to obtain.

To use a 34/48 double, the easiest thing to do would be to use a crankset with a 110mm BCD. The Stronglight Impact Tandem crankset has this (it also has a 74 inner BCD, but you don't need to use it), but I'm not sure about any other tandem-specific models. As well as making the 34 tooth inner ring size easier to obtain by using this BCD, the outer ring will probably work better with this setup than with your current one. This is because 130mm BCD rings that are designed for the middle position are available up to 46 teeth from TA, which is what I use. It sounds like you've put an 48 tooth outer ring in the middle position. This can create problems because the bolt holes in the outer ring aren't recessed on the inner side, so when put in the middle position, the bolts stick out too far and rub on the chain when it is on the small ring. There's a chance that your 48 tooth ring is designed differently so that this isn't a problem, but I don't expect so. However, if you plan to only very rarely use the small ring then this may not be a problem for you.