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Front Derailleur Problem
I recently bought a new frame for my girlfriend which meant the front derailleur from her old bike didnt fit on the new frame. I got another FD from a friend that fitted the frame. It is a shimano deore (dual pull). I have connected the cable from the top of the FD and adjusted it, but it is INCREDABLY hard to shift from the smaller to a bigger chain ring. The shifters are SRAM X7 and when they were on her previous frame with a Sram X7 FD they worked fine.
Does anyone have any suggestions on how to solve my problem?
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If so have a look at this and make sure everything is set up correctly - http://www.parktool.com/repair/readhowto.asp?id=75
Yes the old one was a dual pull. Except when coming from the top it had 'barrel' kinda thing that the cable had to loop around before going to the pinch bolt. Where as the new one doesn't and the cable goes straight to the pinch bolt. To me this would make a difference because the cable has nothing to pivot around. Like there is no mechanical advantage when the cable pulls.
Is this the case?
Everthing is set up correctly. I actually used that very site to guide me thru the set up. I also had a bike shop check it out and they said it was correct too.
It seems like there is too much tension on the cable, but any less tension and the FD wont shift.
I would say you are correct re mechanical advantage. isn't it the case every time you loop around a pulley you double the distance you need to pull but halve the force?
Edit: Looks like I was wrong
The resistance may be due to the chain not "wanting" to move to the larger cog. This could be one or more of the following:
1. moving from a small cog to *significantly* larger cog, would be made worse by a chain that is either too short or a rear derailleur with a cage that is too short to accomodate the cog/cassette combo
2. the FD is not high enough on the seat tube - check that the FD can clear the top of the large cog according to installation instructions
3. the cogs being too far apart - i.e. the FD cant reach far enough to the large cog - check for uneccesary spacers in b/w or a missing middle cog
4. FD still cant reach far enough for large cog - check FD high/low limits and adjust
5. FD still cant reach far enough for large cog - check BB installation & compatibility with FD / frame chainline. frames with different size seat tubes will require different combinations of spacers for your BB in order to achieve the correct chainline settings on standard FDs. You may be having too many spacers on the drive side of your BB, thereby putting your cogs too far away from the FD to reach.
6. I got nothin'
Take some pictures - post 'em up
Could FD cage size affect things? Is it the same as the previous one?
the fd cage size is different to the old one. The reason i couldnt use the old one was because i couldnt get the cage in the correct position due to the clamp hitting the rear suspension linkage. The new FD has a much longer (taller) cage so it can reach the chainrings when its is clamped much higher up on the seat tube. The cage isnt hitting any chainrings and the set up is a standard 3x9 with standard gearing. The frame size is pretty much identical to the old one.
@funkychicken - I will play around with the spacers on the BB and see if that makes a difference. But the problem isnt the chain or FD not reaching the larger chainrings, its that the shifter is really really hard to push. once pushed it changes smoothly.
Some pictures might help, i'll try and get some soon.
Does the shift cable move freely when not connected to the derailleur?
When holding the end of the cable and putting light tension on it can you "shift" through the gears on the shifter without problem and without excess load?
Again without the cable connected can you move the derailleur, simulating shifting movement? Does this move with normal tension? Or does it need cleaning/oiling?
Couple of things to try
I would test it first without the chain. If it is hard then its the derailleur, cable or shifter then do what loki said.
Doesn't Sram and Shimano have different leverage ratios. Like Shimano is 2:1 and Sram 1:1 , or visa versa. I don't know which is which exactly, but you get the idea. Possibly the ratio is wrong for that particular shifter? Or is it only the rear mechs that have a different ratio?
Only the rear derailleur.
Ah, ok.
Thanks for the suggestions guys, will try those few different things and report back.
Cheers.