Fine tuning help

Forums Mountain Bike Forum Fine tuning help

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    • #127046

      Installed shimano XT hollow tech II m770 crankset with ext BB also a new m770 cassette and chain. I have replaced cable and housing. Derailleur is a Deore XT original. I ride a Motobecane dual susp 700 and I’ve tuned and tuned but I struggling with my derailleur and chain staying in selected gear while pedaling under load. Lots of chain slip and chain being thrown off either over the highest cog or lowest cog. I’ve check my limits. I installed my ext BB my self I’ve got a 68mm width. I am concerned my spacing is off, or my derailleur hanger or derailleur is in need of replacement. Any thoughts ideas or suggestions? I am ready to stripping it all off and starting over. Help!

    • #127047

      There is a fairly good chance that your derailleur hanger is bent. Are you adjusting every adjuster to perfection or are you tuning it until it’s good? Also check for play in your derailleur where the derailleur meets the hanger. If that screw has a lot of play in it there is not much you can do. You’ll have to replace in that case. But take note a little play is OK it’s only when there’s a lot of play. When the play is in that screw it keeps the derailleur shifting (but pretty badly) but is impossible to adjust. Here’s a picture of that screw.

      https://plus.google.com/u/0/11248794427 … 9781923312

      Cavermatthew

    • #127048

      Although he didn’t specify, it sounds to me like he’s talking about his front derailleur.

      DCL, It sounds to me like your issue could be caused by not adjusting the height of your derailleur properly. If the derailleur cage sits too high above the large chainring, it will allow the chain to fall off either side when shifting to that ring. If you went from larger chainrings to smaller, you will want to pull your derailleur down until the outer part of the cage is a no more than 5 mm from the teeth of the large chainring when setting directly over it.

      Another possibility is an 8 speed chain on 10 speed rings. The wider chain can roll on the narrower teeth.

      Since you mention cassette, crankset and chain being new, we can rule out mismatched chain & teeth.

      A side pic of the front derailleur when over the largest ring would be helpful.

    • #127049

      Schwim- I am referring to my rear but you may be on to something. I’ll post a picture per your request.

      Caveman- I’ve suspected a bent hanger since putting the system together. I’ve also wondered if my spacing with my BB isn’t right. I took it to my LBS and was given the green light but idk how good he is. Meaning I took it to my lbs with this problem and no solution from their mechanic.

      I am considering taking everything off and starting over and seeing what results are yielded.

    • #127050

      Before disassembly, could you take a picture from directly behind the bike with the gear selection at each extreme end? Take a pic with it on the lowest and then another with it on the largest.

      Your chain alignment could not be so far out of whack that it would fall off both ends of the cassette. It would fall off one end and then climb toward the center of the cassette while on the other end.

    • #127051
    • #127052

      The document is set to private. I requested access.

    • #127053

      I got to look at them. I think your issue is that you’ve extended your limits too far on each side. When properly adjusted, your chainline on your derailleur should be slightly inboard of the gear it’s on at both ends. It looks to me like on both ends, you’ve extended your limits slightly past the gear. This will most definitely cause the issue you’re describing.

    • #127054

      so upon adjusting my limits and that does not cure the problem where/what is the next place to start looking?

    • #127055

      We’ll cross that bridge when we come to it. Your limits are without a doubt too far out on both sides.

    • #127056

      Backed my limits back still falling down the cassette with more of a slack coming up the cage

    • #127057

      I don’t understand the last half of that, could you clarify?

    • #127058

      okay so what i should have said it is continuing to ghost shift after i adjusted my limits. after talking to a guy i ride with he gave me the number of a guy who does some bike repair on the side. getting with him and after going down the trouble shooting line we found the problem. Like mentioned in the original post I’ve got a dual suspension. The both front a rear derailleur cables run down the bottom tube and under the crank set and so forth. The cable housing on my rear was cut per a normal length based on what the previous housing length was. I’m 235 so I would put so much flex in my suspension the BB housing was pushing down on the cable causing it to ghost shift. lengthened the cable problem solved.

    • #127059

      That’s fantastic man! Glad you got it sorted!

    • #127060

      I hate when stuff like that happens. But thanks for your post! Things like this help the rest of us out. No telling who else would have had the same issue. Enjoy your new drivetrain set too. By the way, how do you like the Motobecane?

      Take care.
      -GT

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