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  1. #1
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    Question 30t cassette with SRAM force 10 short cage rear derailleur?

    I know this a common topic, but I have been told it should be ok, and I have read that it could cause major damage, even a crash if it jams.
    I am thinking a Shimano 105 12-30 cassette would be an improvement with my 50/34 compact.

    How stoopid is this? To get the RD farther from a a larger cassette, under the cassette, would I loosen or tighten the B screw?

    Thanks

  2. #2
    tlg
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    I ran a 50/34 with 30t cassette on Sram Red10. It worked fine.
    But all bikes are different. What may work on one may not work on another. The only way to know is to try it.
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  3. #3
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    12-30 Worked fine for me all last year on a giant propel with short cage sram derailleur. 32T also worked but shifting was poor.

  4. #4
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    Quote Originally Posted by deadleg View Post
    I know this a common topic, but I have been told it should be ok, and I have read that it could cause major damage, even a crash if it jams.
    I am thinking a Shimano 105 12-30 cassette would be an improvement with my 50/34 compact.

    How stoopid is this? To get the RD farther from a a larger cassette, under the cassette, would I loosen or tighten the B screw?

    Thanks
    If you run into problems w/ the chain getting pinched between the upper pulley and the cog you need to turn the b-tension screw IN...you can watch the derailleur move back as you turn it in, and move up/in as you turn it out...very easy to do. Some times you just need to experiment and see what happens...turn the screw one way...if it doesn't do what you want, turn it the other way.

    ETA: This thread should be in 'components/wrenching' not 'wheels/tires'.
    Last edited by cxwrench; 04-11-2018 at 09:51 AM.
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  5. #5
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    Thank you! My bad, I did not post in the correct forum

  6. #6
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    and the next time you replace the chain, you might want to lengthen it by a couple links to better accommodate the big-big gear combo (ie, easier shifting into big-big, and less tension means less power sap). Adding a couple links may make the chain droop in the small-small combination, but no one ever rides in small-small

  7. #7
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    Quote Originally Posted by aclinjury View Post
    and the next time you replace the chain, you might want to lengthen it by a couple links to better accommodate the big-big gear combo (ie, easier shifting into big-big, and less tension means less power sap). Adding a couple links may make the chain droop in the small-small combination, but no one ever rides in small-small
    If the chain droops in small/small, the chain is too long. You may want to read through this thread before giving the advice above:

    http://forums.roadbikereview.com/com...ls-364115.html

    As long as the chain does not bind in big/big, it is long enough. There should be a little tension in small/small and at the same time, big/big should not bind. If you can't do these two requirements with the same chain length, then the rear derailleur is out of spec with your drivetrain.

    To the OP, if you are hearing a "motor boating" sound when in the largest cog, you need to turn the B-tension screw in (clockwise) to move the jockey pulley away from the cassette until you stop hearing this noise. If you turn it all the way in and still hear the noise, you can get a longer screw at any hardware store which should do the trick.
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  8. #8
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    Quote Originally Posted by Lombard View Post
    If the chain droops in small/small, the chain is too long. You may want to read through this thread before giving the advice above:

    http://forums.roadbikereview.com/com...ls-364115.html

    As long as the chain does not bind in big/big, it is long enough. There should be a little tension in small/small and at the same time, big/big should not bind. If you can't do these two requirements with the same chain length, then the rear derailleur is out of spec with your drivetrain.

    To the OP, if you are hearing a "motor boating" sound when in the largest cog, you need to turn the B-tension screw in (clockwise) to move the jockey pulley away from the cassette until you stop hearing this noise. If you turn it all the way in and still hear the noise, you can get a longer screw at any hardware store which should do the trick.
    well you're partially right, and I was thinking out of box.

    Yes chain drooping in small-small means chain is too long. But does that mean chain will be too loose and bounce off the cassette? Not necessarily. As long as the tension on the cage is tight enough, chain will not bounce off the cassette, despite chain being too long. Shimano derailleurs apparently allow you to adjust cage tension by taking it apart and pre-loading the cage to a different tension. That's what I did on my derailleur and it solved the loose chain jumping/slapping dramatically.

    Not sure if SRAM der will allow this, in my previous post i was assuming it could be done. This is one of those things that "you just have to try it and find out". I tried it, and I found out it worked for my case.

  9. #9
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    You guys are both right, but one thing I can't stand is putting a longer b-tension screw in a derailleur to make it work w/ a big cassette. In a lot of cases the screw won't even end up bearing on the hanger in the correct spot because it moves the derailleur too far back, then it just moves back to where it was originally. You're also reducing the number of teeth the chain is engaged with.
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  10. #10
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    Quote Originally Posted by cxwrench View Post
    You guys are both right, but one thing I can't stand is putting a longer b-tension screw in a derailleur to make it work w/ a big cassette. In a lot of cases the screw won't even end up bearing on the hanger in the correct spot because it moves the derailleur too far back, then it just moves back to where it was originally. You're also reducing the number of teeth the chain is engaged with.
    you're right about the b-screw. A friend of mine tried to use a 36t mtb shimano cassette with a shimano 5700 med-cage derailleur, and his frame was a trek madone, and he screw in the b-screw all the way in to the point where half the screw was positioned beyond the edge of hanger, and the other half of screw was barely on the hanger edge, and eventually the screw chipped of the edge of the hanger and poke thru the hanger. So his solution was to get the Wolf Component RoadLink derailler hanger extender and he got this setup to work, with still some room to spare on the b-screw.
    Last edited by aclinjury; 04-18-2018 at 02:57 PM.

  11. #11
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    The 30t would not work on my bike, so I may get a medium cage RD. I am also considering a 48/32 compact crank, or I may just avoid the really steep stuff.
    Thanks

  12. #12
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    Quote Originally Posted by deadleg View Post
    The 30t would not work on my bike, so I may get a medium cage RD. I am also considering a 48/32 compact crank, or I may just avoid the really steep stuff.
    Thanks
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  13. #13
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    Quote Originally Posted by cxwrench View Post
    You guys are both right, but one thing I can't stand is putting a longer b-tension screw in a derailleur to make it work w/ a big cassette. In a lot of cases the screw won't even end up bearing on the hanger in the correct spot because it moves the derailleur too far back, then it just moves back to where it was originally. You're also reducing the number of teeth the chain is engaged with.
    Well yes, the longer screw can be turned too far in so it no longer lines up with the hanger. I wasn't advocating going that far in. Yes, it's a hack, but it works to a degree. And yes, it's true that it reduces the number of teeth in contact with the chain. In theory, that could cause poor shifting, but in my case, that hasn't been a problem.
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