Rear dérailleur not working [PHOTO]

[RyanMaloney]

Hi guys,

So I've recently noticed that my rear dérailleur has almost completely lost its ability to shift the chain between sprockets (on a good day, it can move between two of the seven rear sprockets).

I think I've found the source of the problem in the shift mechanism:

[attachment=5372]

In the photo, you can see the dérailleur cable enter a white plastic part (just below the "2"). You can also see some big metal wires emerging from the housing and meeting this white plastic part (just below the "1").

When the dérailleur shift lever tries to pull the cable to the right in the photo, those big metal wires coming out of the housing bash up against the white plastic part and stop the cable from going any further.

My trouble is that I don't even know what those big metal wires are or why they are there. There is no sign of them when the cable emerges at the other end: at the actual rear dérailleur. Does anyone know what they are? What would you advise to fix?

Ryan.

[cny-man]

Those are broken strands of your shift cable. A cable by definition is made of separate wires twisted together. The function of the cable is to move the derailleur, so if the cable is damaged it can't do its job. It may also be corroded or kinked inside the housing. The cable and very probably the housing need to be replaced. You need to make sure you get index compatible shift housing.

[RyanMaloney]

Thank you for your reply cny-man, but I don't think they're broken strands of the shift cable. I've been able to pull the housing back, and the big metal wires go back with it:

[attachment=5373]

If they were strands of the shift cable, I doubt that circa 12 of them could all break cleanly in the same spot (although I can totally imagine why they seemed like strands of the cable from my first photo).

I now think that they are part of the housing that surrounds the actual shift cable. I think that this is intact and is seen inside the white plastic part. Backing this up, a shift cable of the exact circumference of the cable inside the white plastic part emerges at the actual rear dérailleur:

[attachment=5374]

[cny-man]

My error - could not see clearly before. They are indeed the wires of the housing, which have escaped the ferrule, and will indeed ruin the shifting. Need to replace ferrule and possibly cut housing end slightly.