Can you take apart rear derailleurs, and how do you put them back together again? I recently took apart my rear derailleur as it was on a 10 year old bike and really old and stiff.

So I thought I would unscrew both jockey wheels and clean them, they had a silver bit either side, but then when I tightened them back up in the derailleur two things happened.

Either


I completely tightened the bolts on the jockey wheels and derailleur and then the jockey wheels wouldn't turn freely.
Or I didn't completely tighten the bolts on both jockey wheels, and they would turn, so the chain would move.


I ended up going with the second option, Until after a few days of riding the derailleur jockey wheel screw came loose while riding and I lost the silver part on the inside of the jockey wheel. After not being able to replace the silver part on the wheel I bought a new derailleur .

Can derailleur be taken apart and cleaned if really stiff and dirty?

HOW DO YOU PUT THEM BACK TOGETHER AGAIN PROPERLY SO THEY DON'T FALL APART


Some mechanics say don't take them apart. But I say... super stiff and its an allen key bolt designed to be undone. Otherwise why don't they rivet it together?
Others say you can, but use Lock-Tite. I shouldn't need that I don't think or I will end up in scenario (1) again, jockey wheels not moving inside derailleur and chain getting caught.
In my experience the metal caps are mated to the wheels, and while the jockey wheels look the same they are not. Every time I have found the wheels not spinning it has been a simple case of having the wheels in the wrong position or being mated with the wrong bearing cover plates. If you have both wheels not spinning then I think you probably have bearing plates swapped; if one turns and one does not then you might have the plates on correctly but the wheels swapped causing the thicker wheel to be clamped tight while the thinner wheel is barely touching the cage.

I have never used loctite when reassembling bike parts, just care in assembly and a checkup tensioning after a couple of rides. In fact I often dab a little grease on threads to avoid rust binding.

It is probably worth buying jockey wheel replacements if you are servicing a 10-year-old derailleur. If it's a Shimano or something else relatively common chances are you can buy original replacements or even fancy anodised aftermarket parts.