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Old 09-06-10, 08:49 AM   #1
Greenfieldja
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stumped by front derailleur

So here I am in Rabat Morocco and I am one of the very few english speakers with any knowledge of bike repair.

One of my colleagues brought me his kid's mountain bike asking me to true the wheels, adjust the brakes, and tune the derailleurs.

The bike is a Jamis Trail X 1.0 with Shimano Tourney 7spd rear derailleur, shimano undesignated top pull front derailleur, triple crank, and shimano shifter/brake combos that only say 7spd v-brake on them.

The problem is that to get the front derailleur to shift properly the cable needs to be extremely slack. If the slack in the cable is pulled out just by hand so that it is barely taught the derailleur will shift directly from the small ring to the big ring even though the front shifter has only moved one click and is displaying "2". With the cable ridiculously slack (no tension at all) it will shift all 3 clicks and stop properly on the middle ring....but the cable should not be so slack.

I have pulled the cable off the drailleur and adjusted the derailleur height and ensured that it is parallel to the chainrings.

I have pulled the cranks and made sure the bottom bracket (cartridge type) was installed properly. Crank arms were then reinstalled.

For the life of me I cannot get this to work properly.

Resources are scarce here.

Anyone have any ideas?

-j
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Old 09-06-10, 09:04 AM   #2
reptilezs
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sounds fine to me with the cable slack and indexing in all 3 positions. hard to say without seeing it. what shifter is it? the cheap integrated acera ones withe the brake and shifter in one? how much slack are we talking about here
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Old 09-06-10, 09:53 AM   #3
Greenfieldja
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The shifter is the integrated kind...it is unmarked.

I am talking about a rediculous amount of slack...so much so that with no effort you can lift the cable away from the frame about an inch and just flops against the top tube.

the cable is not pulled tight at all when the shifter is indicating "1" that is the only way i can seem to get this to shift through all three chain rings.

-j
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Old 09-06-10, 10:20 AM   #4
waldowales
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If it works, it's fixed!
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Old 09-06-10, 11:56 AM   #5
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Maybe an issue with the FD spring lacking sufficient tension? From your description, it sounds like the FD is not "resisting" the pull of the cable enough, and that spring's what should pull the FD in the direction opposite the cable. If you haven't seen it, this link might help: http://www.parktool.com/repair/readhowto.asp?id=75
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Old 09-07-10, 04:12 PM   #6
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Is the cable attached to the FD in the right spot? If you pass the cable on the wrong side of the pinch bolt for instance, it can substantially change how much the FD moves for a given amount of cable pull. There's usually a notch or slot to indicate where the cable is supposed to sit, but you may have to look close.
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Old 09-07-10, 05:17 PM   #7
Greenfieldja
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Thanks DLM.

There is a small tab that sticks out above and next to the anchor bolt head I thought the cable routed under the tab but routing it over the tab has helped quite a bit.

I think another problem is the section of housing between the top tube and the braze-on on the back of the seat tube is too short as the ends do not seat properly in the braze-ons. I will be back in the states next week for a few day so I will pick them up some housing and new cables. Hopefully this will aide in resolving the problem.

-j
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