jstewse

So I'm reletively new at in-depth bicycle mechanics so I appologize, but this is my first time really fussing with deraillurs. When re-installing my Suntour Vx rear derailleur, I notice that there is this threaded bushing on the inside of the derailluer that makes it difficult to tighten against hanger on the dropout.




Either the bushing tightens up against the body of the derailleur or it tightens up against the dropout, not allowing it to move freely like I thought other derailleurs did.
I can tighten it up so it isn't loose up and down, but it's either rotated down, butting a screw against the dropout, or rotated up.
Neither of these positions create an ideal chain situation as illustrated in the pcitures below. If it makes a difference the front is on the lowest gear and the rear is on the highest



Any help is much appreciated! Thanks

Torchy McFlux

The bushing should rotate freely in that upper knuckle, even when the mount bolt is tightened down. It should not be binding. The spring tension of the lower knuckle puts tension on the chain.
Firstly, I would shorten the chain because it looks like it's too long. It only needs to be able to safely wrap around the big ring and big cog with a link to spare.
Secondly, I'd check the derailleur hanger alignment to make sure it's not out of whack.

jstewse

So the derailleur should be positioned as it is in the last picture, jsut my chain is too long? Thanks for the help.

mcgreivey

The Suntour design is a little different from the Shimano version. Shimano uses a spring on that pivot. Suntour doesn't, and the main pivot spring should hold the b-adjuster screw against the hanger tab when the chain is mounted.

The chain does look too long. Consult Sheldon on the proper length:
https://sheldonbrown.com/derailer-adjustment.html#chain

jstewse

Got the RD mounted up and the b-screw adjusted correctly, and I took out a few links of my chain and everything is in beautiful wokring order!. Thanks for the help guys.

Chris Chicago

this is an old thread but I had the same issue last night. Solved it by taking the bushing and the mounting bolt out, cleaning them both and greasing them up good. mine was a suntour vgx rd