Is this deraileur bent or I am just being paranoid?
I decided to give my bike first elaborate cleaning. Long story short, i removed the wheels and bike tripped on the side of the derailleur. Now i feel(hear) there is some chain rubbing in the rear derailleur cage. When i look from behind i see that the jockey pulley is slightly bent in respect to the casette cogs. I also feel the entire cage is a little bit twisted. Am I just imagining it, take a look at the attachment pic.(IMG_5154)
Another issue is with how the chain lays around the crank. I have read how important it is to replace the chain as soon as it is stretched, but this chain has barely 300 miles on it. Still, it seems like there is a small gap between chain and wheel. Does it look ok to you? (IMG_5156)
too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
It could be the camera angle, but there does appear to be some degree of twist. You can check for yourself by laying a straightedge against the inner cage plate, and comparing to the plane of the wheel. It's easier of you install the wheel backward so the cassette isn't in the way. Rotate the cage so you can check the alignment both vertically and horizontally. If it is bent, odds favor the issue being the hanger and not the derailleur itself.
BTW- if it's shifting crisply and the chain runs smoothly with good trim and no clatter, skip the exercise, since it's a no harm, no foul situation.
As for the chain, the only way to know is to measure, though at 300 miles I'd be shocked if you had a wear issue.
Again no special tools or skill is needed. Get a 12" ruler, and measure 12" of chain. Pull the RD pully back a bit to tension the lower loop and line up the mark with the pins center of edge. Brand new the 0" pin and 12" pin will both line up identically with their respective markings. As the chain wears the links move a bit farther apart (stretch) so the 12" pin will be beyond the 12" mark. Up to 1/16" is OK, beyond 1/16" replace the chain.
BTW- you your chain shows anything beyond trace stretch at 300 miles, you need to either change your lube or apply it more often. Normally you should expect to ride 2,000-5,000 miles before reaching 1/16"/12" stretch.