Chain Rub with Dura Ace Compact Crankset

Discussion in 'Cycling Equipment' started by oldultrarunner, Nov 4, 2011.

  1. oldbobcat

    oldbobcat Well-Known Member

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    Glad to be of assistance. Too bad we took so long.
     


  2. Eichers

    Eichers New Member

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    Hi oldultrarunner, yes compacts, 34/50, appear to be notorious for the chain rubbing against the 50T chainring when on the 34/11. but nice to have for climbing. Yes, the DA7800 RD is very nice, as is the DA7900 FD. It would appear that the new DA9000 is similar to, and even better, than the DA7800 RD and DA7900 FD :)
     
  3. swampy1970

    swampy1970 Well-Known Member

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    An article in Chester Kyles IHPVA journal had a very good article that shot the arguements of cross chaining being inefficient and friction inducing out of the water. Efficiency remained pretty even across the entire freewheel and IIRC, some of the least efficient chainring/sprocket combo's were you'd expect a high efficiency.The article compared lots of different types of transmissions available for bicycle/HPV use. The same journal debunked the theory that some lubes are significantly better than others.
     
  4. swampy1970

    swampy1970 Well-Known Member

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    DA7900 is a little more finiky than 7800 to get the shifting very smooth. The outer cable HAS to be cut with very good cutters and any burred edges filed flat. As an extra step, I run the inner cable through the outer prior to installing and use the end of the inner cable (not the end with the ball that's secured in the brake lever) and 'work it' back and forth at an angle against the end of the outer cable to make sure that the inner telfon liner isn't binding and that the outer metal casing allows the inner to run free if the casing isn't dead square in the brake lever. It only takes a couple of minutes to do all that but I find that excellent shifting from 7900 is attainable all of the time using those steps.

    On some handlebars with tight bends, it can be tricky to get the outer cable to seat correctly causing extra friction and crap shifting. Experiment and use scotch tape to secure the outer cable before taping the bars with regular bar tape.
     
  5. alfeng

    alfeng Well-Known Member

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    Interesting ...

    BUT, how about an actual citation so we (collectively) can see how the test was performed ...

    BECAUSE, as you may know, an HPV (beyond referring to a venereal disease) usually refers to a recumbent-type bike ... and, said bikes usually have exceedingly long distances between the crankset & the Cassette which means that the notion of cross chaining is, at best, moot ...

    And, the excessive-by-comparison chain length introduces additional friction which might itself appear to eliminate a significant difference between any cog-chainring combination ...

    And, the chain passing through the pulley wheels also introduces friction which may influence the interpretation of the data ...

    'I' have to presume the fore mentioned (based on the name of the publication) until you can provide more information.

    So, while Chisolm (in the past) did not think that chainline was particularly meaningful, I will reiterate that:

    • wear is friction ... friction is wear ... unnecessary friction is unnecessary wear ... you may not notice it from ride to ride, but ...
    • worse, friction is lost watts no matter how small the amount.
     
  6. alfeng

    alfeng Well-Known Member

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    It's too bad the "DA7900 is a little more finiky" to set up because I find that the Campagnolo-Shimano combination is a very simple set-it-and-forget-it installation:

    • set the derailleur stops
    • tension the cables
    • DONE!

    As I have noted in the past, while I have used the provided parallel-stranded derailleur cables which accompany both Shimano & Campagnolo shifters, I prefer to use coiled brake cable housing because it is easier to "dress" the ends of the housing AND the larger inner diameter means that there should be less friction than the constant contact which occurs with the parallel stranded housing ...

    • as I previously stated, I thought that parallel stranded housing had been abandoned in the late-(¿?)-70s ...
    • of course, NOKON-or-equivalent housing is an alternative to using brake cable housing -- gee, that's not parallel stranded housing!

    BTW. I find that lightly lubing the cable, regardless of the type (you know, that includes teflon lined housing AND pre-lubed cables), is beneficial.
     
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