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Bottom-pull front derailleur difficult to shift

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Bottom-pull front derailleur difficult to shift

Old 10-17-12, 09:38 PM
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Bottom-pull front derailleur difficult to shift

I recently converted my road bike to flat bars (more upright position to help with neck pain).

The bike has a bottom-pull Dura-Ace front derailleur. The new Shimano LX shifter that was installed by the bike shop is very difficult to shift from small ring to large ring - tough on my old thumb.

Going back to the bike shop for more help is out of the question as it is about 500-km away and in another country. My local bike shop doesn't have a clue.

The LX shifter is a 3-position, but the lowest position is locked out.

I could install a top-pull front derailleur, but there are no lugs on the frame to accommodate one.

Is there any high-mechanical-advantage shifters out there which may work, e.g. SRAM Grip Shifter or Twister? Or any way to put new lugs on my aluminum frame bike? Or even an easy-pull front derailleur?

Just a comment: Bottom-pull front D's, with the wire going around the bottom bracket, are a far poorer design ('pull' requirement, dirt pickup, etc) than the top-pull versions on MTBs.
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Old 10-17-12, 11:37 PM
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To start with Shimano Road front derailleurs and MTB shifters are not compatible (but the the rear road derailleur is compatible with a MTB shifter); currently the LX shifter is pulling almost 50% more cable attached to the front derailleur than a road shifter, which would make the shifter lever more difficult to use and almost impossible to index; you are probably pushing the shifter against the outside stop trying to get the shifter to click. Your best option on a front derailleur is to get a Shimano R series front derailleur (ie R440) which is a MTB front derailleur with a road cage for shifting larger chainrings than the MTB front derailleurs.

Also IMHO, the under the BB bottom pull set up is the best mainly because the housing stops at the top of the down tube, so it's all cable running under the bottom bracket so there is no housing contraction problems, and nothing to clog or keep clean except the derailleur itself. MTB's route the front derailleur over the top so the cable will not be damage when the BB shell bottoms out on something, which is very common.

Last edited by onespeedbiker; 10-17-12 at 11:58 PM.
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Old 10-17-12, 11:46 PM
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Plastic cable guide,as a bushing surface should make it smooth enough.

Die Drawn cables are flattened to be smoother on the surface.

isolate the problem in 2 divisions.
un hook the cable see if the FD itself is not binding..
pull the cable to see if there is binding in the housing
while the 2 are separated..

consider a simple friction thumb shifter, it is a common crossover between road and MTB
compatibility,,

Last edited by fietsbob; 10-17-12 at 11:50 PM.
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Old 10-18-12, 07:20 AM
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Originally Posted by onespeedbiker
MTB's route the front derailleur over the top so the cable will not be damage when the BB shell bottoms out on something, which is very common.
How do you manage to bottom out your BB on something?
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Old 10-18-12, 09:28 AM
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Originally Posted by robo
How do you manage to bottom out your BB on something?
I saw MTB used so I figure the rider might hit rocks, logs, tops of steep hills, that sort of thing. When I have seen MTB riders riding, they do some pretty crazy things.
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Old 10-18-12, 10:28 AM
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Originally Posted by onespeedbiker
To start with Shimano Road front derailleurs and MTB shifters are not compatible (but the the rear road derailleur is compatible with a MTB shifter); currently the LX shifter is pulling almost 50% more cable attached to the front derailleur than a road shifter, which would make the shifter lever more difficult to use and almost impossible to index; you are probably pushing the shifter against the outside stop trying to get the shifter to click. Your best option on a front derailleur is to get a Shimano R series front derailleur (ie R440) which is a MTB front derailleur with a road cage for shifting larger chainrings than the MTB front derailleurs.

Also IMHO, the under the BB bottom pull set up is the best mainly because the housing stops at the top of the down tube, so it's all cable running under the bottom bracket so there is no housing contraction problems, and nothing to clog or keep clean except the derailleur itself. MTB's route the front derailleur over the top so the cable will not be damage when the BB shell bottoms out on something, which is very common.
Correct answer int he first response! Well done!

There one other possible factor (although the derailleur and the shifter are not copatible). Shimano front derailleurs often have the cable imporperly attached, and this causes them to have extremely stiff action. THe cable on a front derailleur should usually go over the little tab on the washer under the cable fixing bolt, not under it. If the cable goes under the tab the cable is then pulling on a shorter lever arm than intended and this makes the derailleur very difficult to actuate. But the shifter and derailleur were actually never designed to work together, so even if the cable is routed properly it won't work well.

You may be able to partially fix the problem by using washers or something to bolt the cable further away from the fixing bolt. In theory this could work but I have never tried it or seen it done.
A bottom-pull front derailleur designed to work with mtb shifters (or a flat-bar-road derailleur) is very easy to get, though, and that is the correct way to fix the problem.
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Old 10-18-12, 10:36 AM
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Originally Posted by robo
How do you manage to bottom out your BB on something?
Well were I ride there are rock gardens and roots that like to jump up and slap the bottom of my MTB bike.
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Old 10-18-12, 10:54 AM
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Originally Posted by onespeedbiker
Well were I ride there are rock gardens and roots that like to jump up and slap the bottom of my MTB bike.
My road bike has brazed on 'loops' as under the BB cable guides and I have done a few things with that bike that I was afraid I had squashed them.
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Old 11-05-12, 02:40 AM
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Originally Posted by onespeedbiker
To start with Shimano Road front derailleurs and MTB shifters are not compatible (but the the rear road derailleur is compatible with a MTB shifter); currently the LX shifter is pulling almost 50% more cable attached to the front derailleur than a road shifter, which would make the shifter lever more difficult to use and almost impossible to index; you are probably pushing the shifter against the outside stop trying to get the shifter to click. Your best option on a front derailleur is to get a Shimano R series front derailleur (ie R440) which is a MTB front derailleur with a road cage for shifting larger chainrings than the MTB front derailleurs.

Also IMHO, the under the BB bottom pull set up is the best mainly because the housing stops at the top of the down tube, so it's all cable running under the bottom bracket so there is no housing contraction problems, and nothing to clog or keep clean except the derailleur itself. MTB's route the front derailleur over the top so the cable will not be damage when the BB shell bottoms out on something, which is very common.
Dear all (onespeedbiker, fietsbob, lardasse74), before too much time goes by I need to thank you for the comments. I now understand the problem(s) and the solution(s). I'm off to the USA in December and will purchase the proper front derailleur and shifters. In the meantime I will check the cable on the front derailleur to make sure it's in the right position on the bolt.
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