LelandJT

A local tandem enthusiast who posts on this forum saw our XTR/Dura-ace Di2 drivetrain that has 30/42/52 rings and 11-40 cassette. He said he likes the wide range a triple offers but likes the small steps of a road cassette and asked if a close ratio Dura-ace cassette could be made to work with a triple Di2 setup. He added that there are others on this forum who would be interested so I should post the results here. I just tested it and it works perfectly. Bear in mind the only triple Di2 front derailleur is XTR which needs a modification to its mount to nicely fit a 50t+ chainring. It's limited to a 10t step between middle and outer rings, hence our 30/42/52 spec. It also requires that you use a XTR rear derailleur and that was the question mark: Would it nicely track a much smaller cassette than designed for? It does, maintaining a nice pulley-to-cog distance throughout.

dvs cycles

What shifter/brake levers go with this set up?

akexpress 

The road DI2 levers will work either the mechanical brakes or hydraulic version as the levers are just binary switches either up or down and are not smart

LelandJT

Dura-ace, but Ultegra would also work or XTR for a flat bar.
What matters Di2 wise is that the only rear derailleur that'll work with a XTR front (and that's the only Di2 triple) is a XTR rear. Ultegra and Dura-ace front and rear derailleurs are interchangable but XTR will only work with XTR. Shifters are interchangable among all three groups.

radsmd

What modification to the front derailleur mount did you need to make?

Chris_W

Which cassette did you try? I imagine that it would work better with an 11-32 than an 11-23.

BTW, I've now used an Ultegra Di2 RD with a Wolf Tooth RoadLink adaptor on a single bike and our tandem with 11-40 cassettes, and it works fine on both. The XTR rear derailleur is therefore not needed to be able to use an 11-40 cassette, but as mentioned, the XTR front derailleur is needed if you want a triple crank and that FD will only work when paired with an XTR rear derailleur.

twocicle

11-26 demo here: https://www.youtube.com/watch?v=A5Hkv77ZM3o

LelandJT

We put a wedge shaped spacer between the derailleur and its band clamp to kick the tail up.

The "close ratio" cassette I tried was a Dura-ace 11-28. I figured that's as small as a tandem will use. It looks like 11-25 would also work.

Yes, I've tested that setup as well as a Roadlink/Dura-ace/K-Edge cage with 11-40 cassette and Santana now offers those options for people on the other end of the spectrum who don't care about close ratios on the cassette but want a double chainring and wide range.

dvs cycles

How about some pictures of this setup and the mods to make it work?

LelandJT

Sorry, I was too busy at work today to do more than take this one photo with the 11-40 cassette. I'm updating the website and teaching myself html as I go. I'm a mountain bike racer and mechanic, NOT a computer guy. Tomorrow I'll take photos of it with the 11-28 cassette and a close up of the front derailleur mount. This bike will be at the North American Hand Built Show Feb 27-29 in Sacramento. Stop by and say hi if any of you attend.

Tandem2

Hey Leland, very interested in doing pretty much this same setup, can you give us a shot of the front D wedge you mentioned?
Thanks
Scott

LelandJT

These are photos are from the derailleur that we mounted on my bike and did the testing with. For production the wedge is now machined and looks more professional but for home use I think photos of this one are more useful because you can make the same thing by cutting a washer (that's what I did).


Here's the wedge we made by cutting a 1.5-2mm thick washer in half and shaving a little material off the sides so it would fit in the slot.


Here it is sitting in the slot ready to have the seat tube clamp slid over it.


Now that the seat tube clamp is bolted to the derailleur you can see that the wedge has made the gap at the bottom (red arrow) greater than at the top. This kicks the tail of the cage up enough to clear a 52t ring.

Tandem2

Thanks Leland, Getting closer to gathering bits for our new bike so trying to get my ducks in a row.

radsmd

Thanks for the pics and explanation. I will drop by this weekend at NAHBS to check out the machine.

LelandJT

A word of caution for non-Santana owners who want to install a XTR 3x11 drivetrain:
It just occurred to me that our bikes use a mountain bike width (73mm) bottom bracket. The derailleur's seat tube mount is mountain bike width. If you put this derailleur on a bike with a road width bottom bracket and cranks it might sit too far outboard. Perhaps the chainrings will still be within the derailleurs range of adjustment or maybe you could space the crank over but I realized that I should let you guys know that's a combo I haven't tested.

twocicle

Don't think this is a problem for many tandems. Typical mtn bike triple chainlines are something like 52mm and road tandem triple cranksets seem to shoot for 50mm, so the difference isn't that much. Also, FSA tandem cranksets (a primary example) are made to accommodate both shell sizes 73 and 68mm, where the latter adds spacers to fill up the extra gaps.

Yes, the mtn derailleurs are not great for shorter axle cranksets (need for narrow q-factor, etc)... TurboTandem has posted one example with his narrow triple + XTR Di2.

dvs cycles

We have a 2007 Team Scandium that came with the clamp for a braise on FD and currently run DA 7803.
Any known issues with our frame?

LelandJT

Good points, I just didn't want people to buy the parts having thought I'd tested and approved that setup only to find out there's an issue.

No issues*. That seat tube clamp is made by us to stick out a little farther because a normal Shimano one is meant for a road width BB and would place the derailleur too far inward for our cranks. XTR was only intended for mountain width chainline so it only comes with a seat tube clamp that places it in this outboard position. Perfect for Santana owners, perhaps a minor hurdle for others (or not?).

*Your bike probably has 30/39/53 chainrings on it now. Remember, we found the derailleur couldn't handle more than a 10t difference between middle and big ring so plan on buying 42t & 52t rings.

dvs cycles

If the cage of a 9070 FD could be swapped with the XTR would that give a better spread of teeth.
All I really need is 50/39/30.

twocicle

9070 FD is a double FD, not triple. It lacks the needed ramps to move a chain properly up from granny and then middle.

Tandem2

I purchased the FSA slk bb30 crankset for my build, it comes equipped 52/39/30.
Will swapping the 52T out for a 50T permit the use of the xtr triple without any mods?
you mentioned a 10T max step between outter and middle rings, can I push that envelope and get away with an 11T step?

shlammed

fsa offers a bb30 tandem crankset?


so they do. neato.

LelandJT

I think​ 39/50 will work but haven't tested that combo. Maybe don't buy a really expensive chainring in case I'm wrong.

If you're gonna use the XTR 11-40 cassette be aware it doesn't have a 12t so while you may have decided that 50&11 is a tall enough top gear your second from top 50&13 is kinda low.

Tandem2

Did you give the oem rings a shot before going 52/42?
Guess it makes sense to start there unless you have already found thats not a workable option.

LelandJT

Or "standard" triple rings are 30/39/53. Those were tried and didn't work. I wasn't present when the XTR setup was first being assembled so I didn't see it. I was just told that it "didn't work". By the time I got to see it they'd already settled on the 30/42/52 setup.