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Di2 RD-6870 compatiblity

pjbpjb Posts: 41
edited February 2019 in Workshop
Can anyone tell me if the Ultegra RD-6870 Di2 (+10-speed, 11-32 cassette) can be used with a Dura Ace 7970 Di2 system?
Thanks
Pete.

Posts

  • ai_1ai_1 Posts: 3,060
    pjb wrote:
    Can anyone tell me if the Ultegra RD-6870 Di2 (+10-speed, 11-32 cassette) can be used with a Dura Ace 7870 Di2 system?
    Thanks
    Pete.
    The Ultegra 6870 is an 11 speed system and Dura Ace 7870 is 10 speed. Which components are you trying to use together?
  • DHA987SDHA987S Posts: 284
    No it definately isn't compatible. The 7870 system uses different wires (and other bits) to the 6770, 6870, 9070 systems.
  • MccariaMccaria Posts: 869
    DHA is spot on.

    All systems after 7970 are broadly compatible (eg you can use 6770 sti and FD with a 6870 RD to get 11 speed). However 7970 has a different cable width and is not compatible with everything subsequent. A disadvantage of going 1st generation !
  • pjbpjb Posts: 41
    edited March 2014
    Ok thanks to all.
    So is there any simple way of using an 11-32 cassette on a 7970 Di2 system?
  • MccariaMccaria Posts: 869
    I don't think the 7970 RD will stretch to 32, the recommended limit is 27 from memory, although I have run 28 with no problem. I have read of people using a medium/long cage and replacing the short cage. Tbh this is beyond my technical comfort level and obviously voids any warranty.

    http://www.bikerumor.com/2012/10/17/hac ... erailleur/

    I am just building a bike for the hills. Ended up buying a 6870 upgrade kit with the medium cage 6870 to go with 11-32 cassette.
  • pjbpjb Posts: 41
    Most helpful, where did you get the upgrade kit?
    Thanks.
  • MccariaMccaria Posts: 869
    I actually bought the individual items from Ribble. 6870 RD medium cage and then matching FD and STI levers. Every few weeks ribble does a circa 10% discount and then prices are very good (RD is currently £133, so with discount came in at £120). This was based on going 11 speed which means additional cost of wheels and cassettes. Unfortunately you cannot do a 10 speed long cage (unless you do the hack I mentioned above) because they didn't do the 6770 in a longer cage and it is the RD which determines whether it is 10 speed or 11 speed.

    I have attached an article I found useful in setting out various compatibilities

    http://carltonbale.com/shimano-di2-ever ... d-to-know/
  • pjbpjb Posts: 41
    Many thanks for the link.
    Had a look at my set-up and no-way will the RD top jockey clear a 32 cog (currently 28 with b-screw at max).
    Thanks again.
  • Mccaria wrote:
    I don't think the 7970 RD will stretch to 32, the recommended limit is 27 from memory, although I have run 28 with no problem. I have read of people using a medium/long cage and replacing the short cage. Tbh this is beyond my technical comfort level and obviously voids any warranty.

    http://www.bikerumor.com/2012/10/17/hac ... erailleur/

    I am just building a bike for the hills. Ended up buying a 6870 upgrade kit with the medium cage 6870 to go with 11-32 cassette.

    Hi
    Could you verify that I can use RD-7970 10 Speed DuraAce with 11 speed Cassette through all gear range without a problem ?
  • StillGoingStillGoing Posts: 5,151
    Shimano doesn't backward convert like SRAM so no. The pull ratio for the 10 speed RD wouldn't match the spacing for the 11 speed shifter.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
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