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  1. #1
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    Di2 & Compact Crank & 11-36 --- Anyone tried it yet?

    Yesterday we were at the flagship store of one of the larger bike shops in the nation where they were changing the BB bearing on our Burley. I made an appointment, drove two hours to get there, and was in and out in an hour. Great service.

    We also went through a set of measurements for a new tandem, which I figure is not too far in the future.

    The bike shop folks told me they have, so far, refitted two CoMotions with Dura Ace Di2 setups, 50/34 cranks, and 11-36 ten speed MTB cassettes with the Di2 rear derailleur. I was told it can be set up to shift flawlessly.

    This is really of interest to me. Has anyone tried it or have any first hand knowledge?

  2. #2
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by Monoborracho View Post
    The bike shop folks told me they have, so far, refitted two CoMotions with Dura Ace Di2 setups, 50/34 cranks, and 11-36 ten speed MTB cassettes with the Di2 rear derailleur. I was told it can be set up to shift flawlessly.
    Ooooh! Not only do I not have first hand knowledge, but I'm thinking that my first house might not have cost that much.

  3. #3
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    Just looking at the costs, it's about a $2,000 for the full set of Di2 7970 shifters, derailleurs and wiring through Performance bike. Comparable cable Dura Ace equipment in the 7900 series would be about $700 or so.

  4. #4
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    Not tried it on a tandem, but I did try a Trek Di2 on a trainer while on a business trip in Sydney. It shifted just like a bike should shift. Yes the chain did not rub, and the drivetrain wouldn't require adjustment but then again my 5 year old 9 speed Ultegra on my tandem works just as well and has only required a twiddle of the tension adjustment and a wipe with an oily rag.

    Then you have to drape a bike designed to take wires with electical cables, junction boxes and a battery that looks like something from a 24h MTB race. Very clever, but not something which is top priority. A garmin, a powermeter if it has to be electronic, or to be honest some new tyres and nice gloves will make more difference to most people's cycling.

    Regarding the compact crank, I'm in two minds - 11-36 is very irritating to ride on the road. But if it reduces Q-factor I like it. I'm guessing the DA mech would need to have a long cage conversion as my road bike one will only take 11-27 and a compact. So figure another $100 or something.

  5. #5
    Senior Member himespau's Avatar
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    I remember reading of a mod that someone made where there was only one shifter because they'd set it up to calculate the gear ratios for you and all you had to do was select up or down. Wonder if that's ever going to come out in production.

  6. #6
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    I'm considering this as well. What shop so I can call? Curious to know what rear deraillier hanger they are changing out with, Ultegra or XTR.

  7. #7
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    Santana was offering Di2 last year when I was at Santana HQ. Played with one on the stand that was destined for Wayne Stetina.
    Santana has modified the rear with permission from Shimano to accept the large rear cassette.
    I hinted as to use with Compact and was told they were looking into it.
    Nice precise spot on shifts but I need a triple and like closer gears.
    Di3????

  8. #8
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    Re. the linked front and rear shifting you need to talk to Fairwheel bikes. But it's not a production system.

    I think Fairwheel would mastermind building you a very good tandem if you asked Jason nicely. The guys there are 2 steps ahead of almost every other shop on the latest and greatest stuff. They also helped Ritterview from here build his super Calfee tandem if I recall correctly.

    Re. fitting a longer cage on the Di2 system, I don't know what they used. I'm guessing here, but I'd imagine that half of the derailleur is pretty standard, so probably most Shimano RDs would fit. See if you can find some pictures and then take a guess

  9. #9
    Tandem Vincitur Ritterview's Avatar
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    Jason at Fairwheel is amazingly knowledgable and innovative. I corresponded with him about the prospect of getting Di2 to work a triple (there isn't any). Fairwheel continues development of their auto-shifting Di2, so stay tuned.

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    This looks promising. Wonder what cage they are using?
    http://blog.acecosportgroup.com/2011...ountain-bikes/
    AM

  11. #11
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    Just curious, noting I've not spend any time investigating Di2 beyond the initial 2X10 Santana offering...

    Is it the Di2 rear shifting performance that most folks are interested in for tandems, the front, or the integration of both?

    Given I have to assume "cost is no object" for a lot of the consumers who are interested in these systems, is there an interim Di2.5 solution to be had by using just the Di2 for shifting the RD with a mechanical FD shifted by an STI lever or bar-end?

    Or, is Di2 so integrated that it doesn't work without both the Di2 FD & RD and both shifters being wired-in to the controller?

    Could it be spoofed into thinking the FD was there to allow a mechanical FD to handle shifting duties?

    Again, Di2 has always struck me as a boon for tandems by replacing the very long RD cables that sometimes causes balky shifting and the need to 'tweak' the downtube cable adjuster every few hundred miles. But, then again, I've never used STI on a tandem so our front derailleur shifts have never been problematic.

  12. #12
    Senior Member WebsterBikeMan's Avatar
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    If I didn't have other issues with Di2 (I'm a Campy fan, I don't like the thought of batteries failing and leaving me feeling shiftless, and then there are the $$$) - I would want it for the integration between the front and back - never having to trim in response to a rear shift.

  13. #13
    Tandem Vincitur Ritterview's Avatar
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    Quote Originally Posted by WebsterBikeMan View Post
    If I didn't have other issues with Di2 (I'm a Campy fan...)
    No problem there, Campy is race testing their electronic shifting now, which bodes well for a release relatively soon. If a tandem is limited to a double with electronic, with Campy it will be nice to have an 11-speed instead of 10. The largest cassette Campy can handle now is 29, maybe with the electronic a larger cassette will be doable.








    FWIW, Di2 will have an Ultegra version, and DA might then be wireless, as prototypes are reportedly being tested.
    Last edited by Ritterview; 04-05-11 at 02:45 PM.

  14. #14
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    Quote Originally Posted by TandemGeek View Post
    Or, is Di2 so integrated that it doesn't work without both the Di2 FD & RD and both shifters being wired-in to the controller?

    Could it be spoofed into thinking the FD was there to allow a mechanical FD to handle shifting duties?

    Again, Di2 has always struck me as a boon for tandems by replacing the very long RD cables that sometimes causes balky shifting and the need to 'tweak' the downtube cable adjuster every few hundred miles. But, then again, I've never used STI on a tandem so our front derailleur shifts have never been problematic.
    While I liked the FD automatically trimming feature I would live without that to have the electric shifting in the rear only.
    Though the levers look to be the same shape on 7900 and Di2 it would feel strange to have one lever that moves and one with touch buttons but could adapt.
    Hope someone with hands on Di2 installation weighs in though I suspect spoofing the computer is not in the cards.

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    Quote Originally Posted by Ritterview View Post
    If a tandem is limited to a double with electronic, with Campy it will be nice to have an 11-speed instead of 10. The largest cassette Campy can handle now is 29, maybe with the electronic a larger cassette will be doable.
    Unfortunately the trend seems to be the other way for Shimano. No DA triple and the 6700 triple is a bit of an afterthought: 53/39 kind of makes sense for a double but 52/39/30 makes no sense at all - why have not have a 42 instead - you still have the 30. The only reason is to save engineering work on the ramps.

    I'd like to see less grouppos and more variety within the grouppo - long and short cage RDs, triple compatible FDs and shifters, chainring options. I know it's hard to justify tandem specific stuff based on the small market, but there have to be a lot of riders that make a bit of a square peg fit in the Shimano shaped hole.

    Rant over!

  16. #16
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    Quote Originally Posted by Ritterview View Post
    FWIW, Di2 will have an Ultegra version, and DA might then be wireless, as prototypes are reportedly being tested.
    Wonder why these electrical systems aren't wireless from the get-go. Seems like an obvious and large advantage. If I have to run a cable, not sure I care so much if it is mechanical or carrying a signal and power. So I'm a buyer when it is wireless. I guess they sell more kit with the incremental approach. Buyers of the wired systems are going to be bummed when the wireless ones come out!

  17. #17
    Senior Member himespau's Avatar
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    wireless is susceptible to interference just like wireless computers. Still that'd make installation easier and the overall look cleaner. Probably decrease the battery life significantly though.

  18. #18
    Senior Member rdtompki's Avatar
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    I would think a combination of battery life and potential liability weighed against wireless initially. We can tolerate some wireless glitches on our Garmins (although I've experienced none), but an inadvertent shift at the wrong time could be a real "problem"
    Rick T
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  19. #19
    Senior Member waynesulak's Avatar
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    I imagine that the two biggest hurdles for marketing the system are battery life and cost. Wireless makes both more of a problem. The wired computer my stoker uses has been running with zero maintenance since 2006. I enjoy working on the bike sometimes but I enjoy riding every time.

  20. #20
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    And wireless would add extra weight due to more batteries. Better to just have one battery to worry about charging or going bad on you.

  21. #21
    Tandem Vincitur Ritterview's Avatar
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    Quote Originally Posted by dvs cycles View Post
    And wireless would add extra weight due to more batteries. Better to just have one battery to worry about charging or going bad on you.
    Many wireless devices (cadence sensor, HRM, etc.) are powered by the CR2032 battery, which weighs 3.3 grams. Likely the FR and RD wireless would be powered by the same battery as powers the motors. If the shifters need a battery, it wouldn't likely weigh much.

  22. #22
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    Regarding batteries and wireless, the issue is that servos under load require high peak currents. So likely the FD and RD work best running from one battery. Also this allows the brain (in the FD in Shimano Di2) to coordinate FD and RD movements, e.g. trimming. So then you would only be eliminating the wire from the shifters to the FD in return for needing 2 batteries.

    Also bike frames are tubular structures, so I expect the solution will be to better integrate the wires, either directly into the frame layup or to pre-plumb the frame and add a standard multi-plug at the head tube, seat tube and dropout. That's what you see over at weight weenies - a few people doing clever things with internal wiring and storing batteries in the seat post.

  23. #23
    Senior Member waynesulak's Avatar
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    Too bad Shimano placed the brain in the FD. I was hoping to possibly get a RD only electronic shifting system with a cable driven triple on the front.

    Wayne

  24. #24
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    So I guess tricking the brain to work with rear only would involve mounting the Di-2 FDsome on the without the cage or moving parts along with a conventional FD.
    Do-able but.................

  25. #25
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    Quote Originally Posted by mrfish View Post
    Also bike frames are tubular structures, so I expect the solution will be to better integrate the wires, either directly into the frame layup or to pre-plumb the frame and add a standard multi-plug at the head tube, seat tube and dropout. That's what you see over at weight weenies - a few people doing clever things with internal wiring and storing batteries in the seat post.
    Doable, but too complicated. I'd be willing to bet that top of the line electric shifting systems will be wireless within five years. Convenience would more than make up for a slight battery weight penalty to deal with peak shifting loads. And as Ritterview points out, the energy requirements for wireless devices are puny now. The CR2450s in my CinQos have lasted a couple of years (OK, I don't ride that much, but still!).
    Last edited by mburchard; 04-12-11 at 04:00 PM.

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