Hey everyone, thought I'ld post up a concern about my chain and see what you all have to say about it (thanks in advance!)
I ride a 9-speed Ultegra grouppo that's about 3-4 years old and has around 5,000 miles on it. My chain snapped off on a climb 2 months back and I got it changed to a brand new one.
A few hundred miles on, I'm spinning on a gentle ride when I downshift and inadvertently dump the chain off and it chainsucks between my 39 chainring and chainstay. After disengaging the chainsuck (it was a very harsh one indeed), I found that I was involuntarily shifting up and down my rear cogs whenever I loaded up the pedals. This was fixed summarily by a few tweaks of my quick-adjust on my downtube.
What now concerns me the most is :
As I stare at the chain as I spin the pedals forward slowly, there is one section (around 20 or so links long) where the chain "rocks" left and right. That is, if the plane of the chain is said to be the plane that sits atop the side plates, the plane turns to face into the wheel, then levels, then faces out. I estimate the angle of this movement to be around 30-40 degrees.
I am expecting that the plane of the chain should be perfectly level at all times, and thus this makes me worried. My hypothesis is that the chainsucking event resulted in some twisting permanent deformation of the chain.
Is there anything I should do about this? I'm concerned about drivetrain wear as a consequence. Since the incident, I've done another 500km or so without event.