jonnyapps

Hi,
I'm trying to index a new (to me) bike, and having some problems. Got it indexed at the back then when I moved the front to the small cog I noticed the chain was 'skipping' on the rear jockey - it's not always aligning with the teeth and sometimes catches on a chain link edge.

I don't have a tool to check hanger alignment, but will look to acquire one, but wanted to check if it's likely to be that?

It's Shimano Ultegra

Here's a video

ThermionicScott 

I like to check for alignment from above, rather than behind. A lot easier to see if the pulleys are in the same plane as the selected cog or not. If the hanger is bent, you'll see more of an angle in some gear combinations than others.

jonnyapps

Thanks for taking the time to reply.
Here's a photo from above.

and another

ThermionicScott 

^ Perfect, that's exactly what I had in mind. The outer end of the pulley cage looks like it's bent outward to me. Switching to the other chainring and going through the gears will help determine whether that's in the hanger or the derailleur itself.

I also find that turning the cranks helps to focus on the path the chain takes.

Iride01 

How old is the bike, or better yet, how many total miles do you think is on it. Though everything else in your pics looks nice, clean and almost new, the pulley wheels in your video looked a little worn... maybe, to hard to really tell. So if they are worn, then that might be the reason for the skip.

Or if that is the old chain on the bike, then it may be worn and stretched (so to speak) and that might be why it is skipping on the pulley wheel.

It's pretty easy to measure a chain to see if it's worn. Put a metal scale next to it and see if the 12 inch mark falls on the same part of the pin as the 0 mark is. If that part of the pin is a 1/16th beyond, then the chain is at or near replacement time depending on your preferences for replacing chains and whether you want to limit how often the cassette and rings need to be replaced.

smd4

That derailleur cage looks really tweaked to me. Doesn't even look like the pulley wheels line up.

jonnyapps

Thanks for the reply. The chain is very new according to the seller, and looks it. Measures up fine as well. Seems to be more about the angle the chain enters the cage than anything. I took the rear derailleur apart and cleaned a lot of crap out, but it's not helped. The jockey cogs seem to have a fair bit of life left in them.

Yes, I think this might be the cause. Could you explain how switching chainrings and going through the gears will help determine whether it's the mech or the hanger? I'm afraid I haven't dealt with this kind of issue before.
Thanks again for the help.

ThermionicScott 

Other people could do a way better job of explaining it, but when you shift chainrings, the rear derailleur cage needs to pivot forward or backward to take up the chain slack. And if the derailleur itself is straight, but the hanger is bent, then the whole derailleur will move at an angle in/out rather than straight forward/backward. So without any fancy gauges, I will check my indexing up and down the cassette from above in one chainring, then shift to the other chainring and do the same. If something is bent, I'll see the chain come to the cassette cog from a slight angle, and chances are good it will index better on one chainring than another.