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When it is warm outside my front derailleur works just fine. But when it gets colder (40F) the lever on the handle bar does not catch and I can move it without any resistance the whole way without the derailleur shifting.

Update: The wire is not moving and the shifter is a Shimano Deore.

Any idea what can cause that and how to fix it?

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    Are you sure its 40F? Water in your cables freezing up does something similar, so I'd try new cables. – Batman Dec 30 '14 at 15:35
  • It is definitely above freezing. – martin Dec 30 '14 at 16:02
  • Do you feel anything in the cable when you try to shift it at 40F? 40F sounds too warm for the shifters to have lubricant gunking up (which is sometimes solvable by flushing the shifter with WD-40). – Batman Dec 30 '14 at 16:39
  • I can see some vague hypothetical situation where the shifter is worn enough that some plastic parts in the shifter itself no longer align when it's cold, but it's a very long shot to there. Sometimes cold can exasperate wear problems since different materials expand and contract at different temperatures. – Deleted User Dec 30 '14 at 17:00
  • They are ten years old. So that could be a possibility. I'll check if the cable is moving on my lunch break. – martin Dec 30 '14 at 17:27
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I had bike with RX100 components where the grease in the brifters dried up and they would not catch as you have described. Its possible the grease in yous is soft enough at warmer temperatures for them to work, but once it cools down, it thickens. There is an earlier post here on how to address it.

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  • I ended up opening the brifter. There is a disk inside with three grooves (one for each gear) and a little spring loaded hitch that catches it. This part was greased up and did not catch the grooves. After cleaning it and putting new grease on it worked like a charm. – martin Jan 2 '15 at 0:35
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I've rebuilt my Campy Ergo Power brifters and understand how they work internally, but you don't say what kind of shifters you have so I can only speculate. There's probably some kind of mechanical coupling between the lever that you push on with your finger and the piece that the cable is actually threaded through. This coupling is probably worn out or (hopefully) needs to be tightened. Due to different rates of thermal expansion, this coupling isn't engaging when things get cold. This is assuming you're riding a bike with trigger style shifters or brifters, some kind of shifter where the lever you push returns to the neutral position after each shift. If you tell me you have downtube shifters it would make no sense unless you're riding a 162 cm Aluminum frame.

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I've had this problem before (recently), and it was solved with a thorough cleaning and then re-oiling of the derailleur.

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    That doesn't make any sense. Indexed shifting happens at the shifter. If the derailleur is the problem, the shifter shouldn't move freely. – Deleted User Dec 30 '14 at 21:58
  • The derailleur was stuck in the furthest "out" position which resulted in a slack cable. The shifter then moved freely. It only seems to click index if there's tension on the cable. – Brian Knoblauch Jan 2 '15 at 12:04

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