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  1. #1
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    under-bartape shifting/ RD cable pull/ ratcheting mech: RED vs 7900

    Hello, all

    Is there a fundamental difference in shifting performance or ratcheting mechanism of mechanical DA7900 vs SRAM red?

    Some background:

    I have most of a DA7900 groupset sitting on a table next to me.

    I need to build a fairly fast folding bike for a daily multimodal commute.

    I contacted Bike Friday to see if they would use my existing groupset for a bike build.

    They said that while they have no problem using my groupset, they could not use the new Shimano stuff:

    The problem with 10-speed Shimano stuff is that a few years ago they went from the cables coming out of the side of their levers to internal cable routing for a cleaner appearance. Internally, the shifters work essentially the same as they did before and the cables make a double-bend which gives horrible laggy performance. As a result, we don't do 10-speed Shimano Integrated Shifters on any of our new bikes. With the double-bend internally, coupled with extremely long cable routing on our bikes, the system doesn't work like it should.
    This is a solid argument, however their site has a SRAM red model (which appears to have under-bartape cable routing)

    So this makes me wonder: Either there has to be a fundamental difference in cable routing of SRAM or 6700, or there is a difference in the internal ratcheting mechanism, or perhaps DA is just too much of a pain compared to SRAM to set up

    Thoughts?

    Edit: I just wanted to add that I think that the folks at BF have been great in communication, even when we were not yet discussing building a folding bike. This thread is just to get more information on the issue (and possibly see how I might try to convince them to build up the bike, and if I am foolish for doing so)


    http://bikefriday.com/bicycles/road/1266
    Last edited by guitarplayerone; 05-24-12 at 04:52 PM.

  2. #2
    Senior Member
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    sram pulls more cable per click so it is less senstive to cable friction. shimano 10sp road is pretty picky about cable friction.

  3. #3
    Senior Member JTGraphics's Avatar
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    I really don't think Sram has more cable pull over Shimano on road setups if that were the case you would not be able to mix the group parts up.
    I have my cables installed as in the photo above and shifts are great.

    It may not be fancy but it gets me were I need to go.
    http://www.jtgraphics.net/cyclist_bicycles.htm

  4. #4
    30 YR Wrench BikeWise1's Avatar
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    Quote Originally Posted by JTGraphics View Post
    I really don't think Sram has more cable pull over Shimano on road setups if that were the case you would not be able to mix the group parts up.
    I have my cables installed as in the photo above and shifts are great.

    For now. Those overpriced Gore cables are marketing hype gone bad. I just pulled a set off of a Madone that were rusty beneath the lining. They weren't even stainless! He had terrible shifting issues until I installed a simple and inexpensive set of Jagwire die-extruded stainless wires with the pre-lubed housings they sell. We finish the ends flush on a grinder and use ferrules without o-rings. Shifting performance is flawless and the setup easily maintained with one of these:

    6698LPEN-250x250.jpg

    I also find a little Dura Ace "Special Grease" or Buzzy's Slick Honey or similar where the cable exits the lever over the white plastic piece to be critical for best shift performance with Shimano. I agree that without careful setup, shift effort is much higher-we measured 3X the force at the shift lever-than 7800.

    If you work on bikes long enough, you'll realize SRAM has not got the road thing figured out nearly as well as Campy or Shimano. I have a 35 year old Schwinn Volare with Gen 1 Dura Ace parts on that after all this time and a lot of miles have less slop in the derailleur pivots than brand new RED parts....

    I don't know where you got the idea that SRAM and Shimano cable pulls are "close". They aren't even close to close. :-)

  5. #5
    Senior Member JTGraphics's Avatar
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    LOL people make me laugh sometimes while the casing may be gore that came with my Sram Red group the inner cables are actually Aztec PTFE-Coated cables which work well but thats OK, you are bikewise and seem to know a lot about cables
    It may not be fancy but it gets me were I need to go.
    http://www.jtgraphics.net/cyclist_bicycles.htm

  6. #6
    Gear Combo Guru Chris_W's Avatar
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    SRAM (and Campagnolo) rear shifters do pull more cable than Shimano. To ease problems of cable friction and tight bends then use Nokon cable housing - it's expensive and takes a while to install but it works really well.

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