Rear Derailleur.. I have no idea what I'm doing

[jjc5]

Hey guys, I'm a total novice when it comes to working on bicycles and I read through a lot of posts and I watched some youtube videos but I am really confused on how to get my derailleur back on.  I was trying to get my back tire off to change the tube and some how the derailleur inadvertently "fell off".  Also, a small metal piece fell off with(I did not see any screws land anywhere), which I have no idea where it goes or what it is for.

I don't know hardly any of the biking terminology so it has made it even more difficult for me to understand what I need to do to get it back on properly.  I'm really hoping someone here can help me out!  

I've attached some pictures of what I am dealing with.  It's a mongoose mountain bike, I'm unsure of what model.

If you need more information or pictures please let me know.

[elmore leonard]

that item in your hand is what the derailleur bolts to. it slides up first, into the same dropout the wheel axel slides into. it fits into the drop out with the narrow side facing the deraileur bolt and the curved side facing rear. your missing the bolt? Maybe one of the pros here can explain it better.

[cradom]

Second pic: Axle spacer, to keep the axle slightly forward to keep the derailler aligned properly. Should be a screw, probably isn't one.
First pic: The hole where your thumb is should go under the axle nut between the nut and the dropout (part with the slot that the wheel fits into).

[Selenium]

Did you end up figuring this out?

Literally just joined this forum to ask the same question. Removed the derailleur without paying attention as to how it was secured to begin with and mine has the same sorta hook as yours does. None of the guides online seem to have that kind.

[elmore leonard]

(04-13-2015, 03:03 AM)Selenium Wrote:  Did you end up figuring this out?

Literally just joined this forum to ask the same question. Removed the derailleur without paying attention as to how it was secured to begin with and mine has the same sorta hook as yours does. None of the guides online seem to have that kind.

The axel spacer, the piece the original poster is holding in his hand should have a small screw/bolt that you screw into it to hold the two pieces together so you can slide them up into the wheel drop out. Curved sides facing rear. Then tighten.This will set the position of your rear wheel axel when you slide your rear wheel back into the wheel drop out..