Salsa Powderkeg Tandem gravel conversion - parts suggestions?

[jbreebs]

My buddy recently came into possession of a Salsa Powderkeg, and now he and his wife want to convert it to a drop-bar gravel bike using modern components. I'm helping him decide what parts to use, and we've run into a few stumbling blocks.

He's fairly set on a 2*11 drivetrain, with something like a 30/32-44/46 crankset and 11-36(40?) in the back. We've run into two main issues - finding a rear der that can handle that range of gearing paired with a road shift/brake lever that is compatible, and finding tandem cranksets that will generally make that possible. The crankset arm/spindle (atleast the stoker chainset) needs to have mtb - width Q factor to clear the chainstays, as well as a larger than "mtb standard" chainrings to run the desired 32-44 chainrings. I've suggested that the new shimano rx/grx gravel group might work well on this bike - does anyone havee experience with this group yet?

He's also tentatively open to doing something like a 1*12 using sram axs, which will eliminate the cable tension issue, but raises other issues of its own (finding a super long hydraulic hose, and the crankset issue). This would probably mean something like a 40-42t chainring and 10-50 cassette.

I suggested possibly using two driveside arms from a cinch crankset, to run the normal chain DS and the timing chain on the NDS. This would require a right pedal spindle getting swapped onto a left pedal body, but beyond that I think it would work. However I've never messed with those cinch cranksets - can anyone verify that you could indeed put a DS arm on the NDS side?

Another option would be running both the timing and normal chain on the DS. If a 2*11 setup, using a triple crankset with the outer two chainrings as the main drive chainrings, and innermost chainring for the timing chain. If a 1x setup, using a 2x crankset with the inner ring for timing and outer for the main drive.

Does anyone here have suggestions? Have I not thought about anything; have I missed something important?
I've never done a tandem setup before, and while I'm fairly competent in component compatibility this is a little trickier than most projects I've worked on before.
Thanks!

[josephr]

I'd think with gearing that low on a tandem for gravel is overkill...unless they can both spin at 120 and intend on climbing the Matterhorn. Your basic Deore/XT RD with a 34/36 on the back should be just fine.

[stien]

My wife and I have two tandems: one Burley Rock N Roll that we set up cruiser (3x7 Suntour XCD) and a Paketa road rocket that I set up recently with Di2 2x11.

I suggest that you recommend they ride it first to get a feel for gearing. Together we can push a ton of gear and I feel like anything over 1:1 is pointless. The Burley tandem has a 56t chainring because of the 26" but the road bike I have set up 50/32 with an 11-34. We are planning to do a 113 mile 8000 ft climbing ride on it this fall. Going to the small ring outside of the mountains is a bit silly admittedly. I'm going to swap the 32t out for a 34t.

I'd probably go 46/36 with an 11-36 out back if I were doing something more gravel oriented with 650b or 700c tires. Buying new tandem cranksets gets silly expensive so it would be ideal to work with what's there already. Whats the current setup?

If they want to go whole hog, I highly recommend di2 because it'll allow using drop bar levers with a MTB derailleur set. We kept our stock FSA tandem crankset and just changed the rings and it works well with Di2.