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Old 04-23-14, 05:44 PM   #1
will2build
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Front Derailleur Problem - Spring has a mind of it's own!

First time poster, having learned a lot from the forums over the years. I’m posting with a problem with the function of a Shimano Deore XT front derailleur. This is the original on an ’83 Specialized Stumpjumper (triple chainrings, friction shifting). Regardless of the shifter position, the spring on the derailleur wants to pull the chain inward (towards the seat tube) and onto the smallest (granny) gear. Thumb shifter seems to work well –I can shift up to a higher gear/larger chainring but have to hold it in place in order to stay in said gear. If I let go, the spring on the derailleur pulls it back onto the little chaining. I can ride the bike, but I just have to hold the shifter in place, which makes for a very sore thumb!

Any suggestions? How does a derailleur resist the force of its spring? Could the derailleur be worn out or broken? It looks to be in good condition but I don’t understand the spring mechanism enough to know if there’s a problem. I can post more pictures if that helps.

Thanks in advance!
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Old 04-23-14, 06:38 PM   #2
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Don't blame the spring, it's just being a spring.

The spring's pull is constant, you pull the cable to shift and let it go and the spring shifts back. It's a latching mechanism in the lever that holds the cable against the spring. So look to the lever for the solution. It could be dead, or (if you're lucky) gummed up with dried grease or dirt, so the latching mechanism doesn't engage right. Sometimes the levers respond to being blasted with WD-40 or the like to flush out any gunk, then dried, and oiled with a light oil.

You have nothing to lose except the cost of the solvent, so give it a shot. Otherwise start shopping for a replacement lever.
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Old 04-23-14, 07:02 PM   #3
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Look for a little "D" ring on top of the shifter to increase tension.
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Old 04-23-14, 07:06 PM   #4
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Quote:
Originally Posted by Bill Kapaun View Post
Look for a little "D" ring on top of the shifter to increase tension.
The OP didn't say, and I'm far from a Shimano expert, but wouldn't a Deore XT system be index?
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Old 04-23-14, 07:16 PM   #5
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Quote:
Originally Posted by FBinNY View Post
The OP didn't say, and I'm far from a Shimano expert, but wouldn't a Deore XT system be index?
Probably not the front in 1983.

Could be a 'D' ring or plain old screw that needs tightening.
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Old 04-23-14, 08:31 PM   #6
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Originally Posted by FBinNY View Post
The OP didn't say, and I'm far from a Shimano expert, but wouldn't a Deore XT system be index?
OP specified friction.
My 86 Rockhopper was still friction. 87 not.

http://en.wikipedia.org/wiki/Shimano_Deore_XT

I expect it's like this?
https://www.flickr.com/photos/kristina_nash/7065523767/

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Old 04-23-14, 09:25 PM   #7
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So that's what those D-rings are for!
Ya'll were spot on - the whole assembly was loose to the touch. I unscrewed the D-ring, noted a little corrosion, moved the lever - nice ratcheting sound - wiped off any crud, lubed, and oiled everything up. Same for other side. Works like a dream.
Thanks for your help everyone! And yes, deerhead friction thumbies as referenced, Bill. Here's a pic:
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