Understanding derailleur hangers and types

[tomjasz]

I have what I think are upgrade derailleurs over those KHS has downgraded to. But I'm confused. The hanger bolts are positioned differently and there are some body size differences.

First, are these slightly used derailleurs an improvement?

Second are they compatible?

I took dome photos and hope they are sufficient. The black frame is an earlier version KHS Smoothies and the derailleur seems ok. The cam parison shots are on a 2016 version and every component is a downgrade from previous years.

I'm learning but need a better understanding.

 

[tomjasz]

The alvio derailleur does not have the section shown in this photo by the red arrows.

 

[Chalo]

First, are these slightly used derailleurs an improvement?

Yes, as long as they're not bent or damaged.

Second are they compatible?

Yes. They'll work with the same shifters and sprocket spacing.

If you're using a front derailleur, then there are further variations you have to take into account. The front derailleur must have a clamp diameter equal to or larger than your frame's seat tube diameter, and it must correspond at least approximately to the chainring sizes you have.