I fitted a new chain and afterwards noticed that the rear mech seems to be angles back more than it was (see pics). I can't think why this has happened and the mech doesn't seem to want to move in that way at all. I am going to remove it tomorow and see if I can find what is wrong but wondered if any one has any idea?

thanks

before and after pics

Your new chain is longer than the old one.

+1. Did you install the new chain full length as it came in the box? If so, it's longer than the old one and longer than it should be.

Look here and scroll down to the paragraph titled "Chain Length".

https://www.sheldonbrown.com/derailer-adjustment.html

I think it's because the chain is not on the same cog in the two pictures.

Al

in the second picture looks like the chain it is between cogs.

Solved it today (I think).

The problem was that the body of the mech was angled back. Shortening the chain just pulled the cage forward.

After looking at it again today I decided to take the whole mech off the frame. However, when trying to undo the allen key it instead rotated the mech. It was obvious that the body of the mech was corroded on to the bolt. I did manage to get it undone although it took a lot of force. I then dismantled the mech pivot/bolt. To get the botl out I had to use a hammer. There is a steel sleeve running through the mech body and this had rusted. If it had got much worse I wouldn't have been able to undo it and probably would have had to take the bike to a shop and have them cut the derallieur off.

Having cleaned the rust out and lubed it it seems to be working ok now. Just one of the wonderful things you can discover on a 2nd hand bike.