Sram 11-32 with a Dura Ace derailluer

Discussion in 'Cycling Equipment' started by Desertrider 119, Apr 26, 2011.

  1. Desertrider 119

    Desertrider 119 New Member

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    I'm about to do a ride with a 5 mile 5% to 7% climb. That's tough for me at 64. I've been told that I can replace my Shimano 11-28 cassette with a Sram 11-34. All that is required is to back the "B" screw out to allow the derailluer to clear the 34. Sounds reasonable to me, but I would like to hear from some one who has used this combo.

    The second gear on the Sram is 28, same as my current low gear and I intend to use the 34 as a bail out when my heart rate gets too high. Have any of you personally tired this combo and what do you think?

    The chain rings are 50-34 and I realize that I need to not go from the 50 chain ring to the 34 rear.

    Thanks in Advance
     
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  2. Eichers

    Eichers New Member

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    Hi Desertrider 119, you can refer to this thread for a lot of details ... http://www.cyclingforums.com/forum/thread/477148/an-alternative-to-using-a-compact-crank-set/105#post_3996625 With your 50-34 compact crank using the 34 front to a 28 rear is equivalent to a 39 front 32 rear (approx). So, using a 34 front to a 32 rear is equivalent to a 39 front 36 rear (approx) :) If you have a short cage (SS) DA RD it will not work with an 11-32 cassette. If you have a medium cage (GS) DA RD it will, although this will depend the dérailleur hanger (please read the posts in the above thread). If you use an 11-34T cassette it is best to change the 11T guide pulley/jockey wheel to a 10T campag guide pulley/jockey wheel, so that the guide wheel requires less B screw adjustment to clear the 34T sprocket. Happy reading and please post any questions in the above mentioned thread :)
     
  3. Desertrider 119

    Desertrider 119 New Member

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    Thanks KLabs... How do I tell the difference between a (SS) DA RD and a (GS) DA RD? The bike is a 2011 Specialized Roubaix SL3 Pro DA
     
  4. Desertrider 119

    Desertrider 119 New Member

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    KLabs... I just looked it up on the Shimano site it is a 7900 SS.
     
  5. Eichers

    Eichers New Member

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    Hi Desertrider 119, unfortunately a 7900 SS will not work with an 11-32T cassette :) The 7900 DA SS RDs total capacity is 33T. If the Front is 50-34 = 16T and Rear is 11-32 = 21T, this requires a total capacity of 37T (16T + 21T). An 11-32T cassette would work with a The 7800 DA GS RD which has a total capacity is 37T :) You can also do what has been suggested in the posted thread ... that is use a Shimano 9spd XT or XTR shadow RD and a Sram or Shimano 11-32T, 11-34T, or even an 11-36T 10spd cassette.
     
  6. Desertrider 119

    Desertrider 119 New Member

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    Thanks again. This is where it gets confusing for non bike specialists like me. I was told that the new 7900 braker/shifter will not work with a 9 speed cassette.

    Additionally the So Cal shop where I have my work done says they have installed the 11-32 on several bikes and the only caution is not to try to go from big (50) to big (34). They insist that the 34/34 is well within the capacity of the Derailluer to take up the slack in the chain. I guess I'll have to either pass or try their setup and see if it works.

    Again, thanks for the info. I guess the ball is in my hands now.
     
  7. Marco Foa

    Marco Foa New Member

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    we are talking here of 9 speed derailleur ( that can work with 10 speed shifters ans 10 speed cassette) not a 9 speed cassette
     
  8. oldbobcat

    oldbobcat Well-Known Member

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    I've done the old flip-the-B-screw kludge to extend the range of a rear derailleur, but only with a gun to my head. I don't recommend it, especially if it comes with the "just don't ever use the big-big combination and you'll be fine" caveat. Someday you'll be motoring into a headwind on the big ring and you'll absent-mindedly flip the lever for one more cog on the back, and it will be the first cog, and the whole drive train will grind to a halt and something expensive will get broken. I'd rather cut the chain longer and just tell the customer to stop using the small ring in combination with the last two or three cogs. That way, if you end up there, you just get a lot of noise from the chain rubbing against itself and slapping the chain stay.

    Pushing the range of the rear derailleur works better on some bikes than others, the key factor being the distance between the axle and the derailleur pivot hole.

    All Shimano 9- and 10-speed road rear derailleurs are cross compatible. All Shimano 9-speed MTB rear derailleurs are compatible with the 9- and 10-speed road derailleurs. Only the fronts are a different story. To me, a Deore or Alivio 9-speed medium or long cage rear derailleur and a 10-speed MTB cassette (either Shimano or SRAM) is a cheap investment to getting the proper reach to the 34t cog and sufficient chain take-up to use most of the cassette with the small ring, without chain-slap and without performing heroics with the B-screw that may or may not waork.
     
    dhk2 likes this.
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