It would be nice to upgrade the transmission on our tandem with an 11-speed cassette, possibly even Di2 like I have on my single bike that I really like. The problem is finding a 145mm tandem rear hub that can take an 11-speed cassette but that doesn't cost several hundred US$, or finding an 11-speed cassette that can fit on our 10-speed hub.
Our current hub is a Shimano model, so there is no chance of changing the freehub body for an 11-speed version. I've seen that the top-end American hub manufacturers (Chris King, White Industries, and Phil Wood) all offer an 11-speed Shimano tandem rear hub, but the prices are US$300 to $600. Since we live in Europe, I don't really care if something is made in the US or in Taiwan (or in Europe actually, it's all the same to me). Isn't there an Asian option at half the price? I couldn't find one. I guess it's because these are not really a mass-production item.
I've read conflicting info about whether the DT Swiss 540 tandem hub has an 11-speed compatible Shimano body. Can anyone confirm whether this is correct? I know that it can take a Campagnolo 11-speed body, but that limits cassette range to Campy's new 12-30 11-speed cassette, which is much narrower than what you can get with Shimano 10-speed cassette, so it wouldn't be worth taking a DT Swiss hub if it can only use a Shimano-10 or Campy-11 body. In addition, I'm not a big fan of DT Swiss hubs due to the difficulty involved in disassembling them, but it would be nice to know whether or not it is an option. EDIT: The confusion was caused by DT Swiss listing the hub as being Shimano MTB 9/10/11 speed compatible, which means that's it's a regular Shimano 10-speed body, and so it can take an XTR 11-speed cassette but cannot take any road 11-speed cassettes (except Edco, see below).
I've modified 10-speed freehub bodies on several single-bike Shimano hubs that I own (an XT, Ultegra, and a Dura Ace) to take 11-speed cassettes by filing 1.5mm from the back of the splines (as long as you're using a 28- or 32-tooth cassette then there is no concern about the cog, chain, or derailleur ending up too close to the spokes IME), but there is no space to do this on the Shimano tandem hub that we have.
I have found a couple of options for putting 11-speed cassettes on Shimano 10-speed bodies. The new XTR 11-speed 11-40 cassette is one such option, and I believe that this may work with our current X-9 10-speed rear derailleur if I replace the shifter with a SRAM 11-speed road model, so this could be the cheapest way to go 11-speed. Also, if I switched the first few cogs on the XTR 11-40 with those from a 105 12-25 11-speed cassette then we could have a pretty nicely-spaced 12-40 cassette. However, I'm not 100% sure about getting the shifting to work, so it could be an expensive failed experiment. I may wait until late 2015 when the XT version of this cassette inevitably gets released for half the XTR price since we have no need for the weight-saving of the expensive titanium cogs.
Edco are also offering 11-speed cassettes that fit on Shimano 10-speed bodies,
see here. Their website only lists up to 11-28 sizes, but I've seen an 11-32 listed on an order form that they sent to the bike shop where I work. However, I've never found shifting to be that good on cassettes from small brands like that, plus their 11-32 11-speed cassette still has the dreaded 19-tooth to 22-tooth jump/gap between cogs, like so many 10- and 11-speed SRAM cassettes also have, which I absolutely hate (it's a 15.8% change in cadence!). This jump is right in the middle of the cassette and is so unnecessary when you have 11 cogs (Shimano's 10- and 11-speed 11-32 cassettes use the far better 18-20-22 spacing instead, and put the slightly larger jumps at the less-used ends of the cassette). I've vowed never to use a cassette with that spacing again, so the Edco option is out for me.
Looking at wide-range 11-speed cassettes, SRAM have announced that they are launching an 11-36 11-speed cassette to go with their 1x11 cyclocross group, and
IRD now offer 11 or 12 to 34 or 36 tooth 11-speed Shimano cassettes, but all of those appear to require an 11-speed Shimano freehub body. Plus, I've found IRD's 10-speed cassettes to shift far worse than the Shimano equivalent, so I'm betting that the same is true for their 11-speed stuff.
Does anyone else have more info/ideas of what other options there are? I know that the easiest thing would be to just buy one of the fancy US-produced hubs, but I'd like to try to find another solution if possible. Keeping our current Shimano hub would be ideal becuase I prefer to use loose-ball, adjustable hubs whenever possible.
BTW, there is one old BF thread on this topic
here, but I decided to make a new thread since the info in the old one is a bit out of date and I've made this is a bit more general by including options with special cassettes.