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  1. #1
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    What 10 spd rear derailleur with Dura Ace 7801 to be able to use a 11x34T w/CX 48/38?

    I have a CAAD9 CX bike (2 ring 48/38) that I'm using as a commuter and dirt road training. What Shimano mtb or road rear derailleur can I use to use a 11x34 cassette? Is a road link also required?

    Thanks

  2. #2
    'brifter' is a lame word.
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    Quote Originally Posted by CXmudder View Post
    I have a CAAD9 CX bike (2 ring 48/38) that I'm using as a commuter and dirt road training. What Shimano mtb or road rear derailleur can I use to use a 11x34 cassette? Is a road link also required?

    Thanks
    This has been covered dozens if not hundreds of time. If you've got 10 speed road shifters and you want to use a 34t cassette you need to get an 8 or 9 speed mtb derailleur w/ a cage long enough to handle your specific capacity... which is 33t. You can easily handle this w/ a Shimano Deore RD-M591-SGS 9-Speed Long Cage Rear Derailleur . If you can find a GS cage that should work as well, like this: Shimano XT RD-M772-GS 9-Speed Medium Cage.
    DO NOT buy a 10 speed mtb derailleur, DynaSys does NOT work w/ the cable pull ratio used in any Shimano road shifter.
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  3. #3
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    Thanks cxwrench...I've been riding Campy for sooo long and this is my first Shimano bike. I'll search better next time...was frustrated -my LBS just hemmed and hawed - only want to sell new stuff.

  4. #4
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    Quote Originally Posted by CXmudder View Post
    Thanks cxwrench...I've been riding Campy for sooo long and this is my first Shimano bike. I'll search better next time...was frustrated -my LBS just hemmed and hawed - only want to sell new stuff.
    Sucks when the shop guys don't really know what works. You're supposed to be able to trust them for info, but...not all of them know what works and what doesn't. That Deore derailleur is cool cuz it uses the same cable routing as a road derailleur and has a built in barrel adjuster. The XT is a Shadow derailleur, so it doesn't have a barrel adjuster built in.
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  5. #5
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    CX is right. Go with the 9-speed Deore rear derailleur (M591-SGS). Shimano 8, 9 and 10 speed road systems, and 8 and 9 speed mountain systems have the same rear shifting pull ratio. Shimano changed the pull ratio for mountain 10-speed and road 11-speed.

    To be fair, the search function on RBR sucks. It doesn't filter much and it could take literally days to read through all the results in order to find what is relevant to your issue. That's not to say a Google search wouldn't work. When I use Google, it often refers me to the relevant RBR thread!! Google is still my best friend.

    Shop guys? It all depends on the shop. I am blessed with an awesome shop, but there are plenty of shops out there with hacks. CX, I'm sure you are often shaking your head looking at some of the eff-ups riders bring into your shop.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

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  6. #6
    'brifter' is a lame word.
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    Quote Originally Posted by Lombard View Post
    CX is right. Go with the 9-speed Deore rear derailleur (M591-SGS). Shimano 8, 9 and 10 speed road systems, and 8 and 9 speed mountain systems have the same rear shifting pull ratio. Shimano changed the pull ratio for mountain 10-speed and road 11-speed.

    To be fair, the search function on RBR sucks. It doesn't filter much and it could take literally days to read through all the results in order to find what is relevant to your issue. That's not to say a Google search wouldn't work. When I use Google, it often refers me to the relevant RBR thread!! Google is still my best friend.

    Shop guys? It all depends on the shop. I am blessed with an awesome shop, but there are plenty of shops out there with hacks. CX, I'm sure you are often shaking your head looking at some of the eff-ups riders bring into your shop.
    You're lucky to have a great shop, and yes...I do see SMH stuff pretty much on a daily basis.
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  7. #7
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    Quote Originally Posted by cxwrench View Post
    You're lucky to have a great shop, and yes...I do see SMH stuff pretty much on a daily basis.
    VERY lucky. I reward them well.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  8. #8
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    Quote Originally Posted by cxwrench View Post
    Sucks when the shop guys don't really know what works. You're supposed to be able to trust them for info, but...not all of them know what works and what doesn't. That Deore derailleur is cool cuz it uses the same cable routing as a road derailleur and has a built in barrel adjuster. The XT is a Shadow derailleur, so it doesn't have a barrel adjuster built in.
    Thanks - I trust these guys to do the work or sort things out I can't. But, when they try and sell me a new bike or group upgrade before giving this kind of advice - then they may have lost a loyal customer. I've always done most of my own work until the past year or so. Bought the parts at the LBS with a club discount for my new builds and repairs. Newer tech like hydro brakes and increasing gear ratios requires a bit more time and finesse. I just want to ride and know enough to make adjustments and basic repairs. No need for $$$ esp. for an older bike.
    Thanks again - found a new Deore

  9. #9
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    Also, the XT RD that I have on my CX bike does not have a barrel adjuster. With the 7800 shifter, you probably already have an inline one up front, but you may need a second inline barrel adjuster. That's what I have with my 5700 shifters and 9 speed XT RD. The real trick is getting a smaller chain ring, if you want to do single track. I got a 46-39-26 triple and modified a Shimano CX FD to shift alright. It took some grinding and bending, but there's no MTB FD that works with Shimano road shifters.

  10. #10
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    Quote Originally Posted by CXmudder View Post
    But, when they try and sell me a new bike or group upgrade before giving this kind of advice - then they may have lost a loyal customer.
    SMH. That's what I really like about my shop. They will take an older bike that other shops think belong in the scrap heap and bring it back to life. Many high mileage commuters with older bikes are loyal customers at my shop. The owner tells me he loves the challenge of making an older bike rideable again.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



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