Okay 50+rs, I need your wise experience.
I have been using my Windsor Leeds road bike as a trainer for two winter seasons, plus using it as a "utility bike" during the rest of the year. About 2,000 outside miles on it. Unknown indoor trainer miles, but I use it regularly. It has been working fine with no problems. It is a Sora (8 speed cassette), triple, circa 2004.
Tuesday am I went to get on my trainer. As I worked through the chain rings and got on the small CR and was shifting back to the middle CR, it sucked chain something terrible. It really jammed in the space between the small chain ring and the middle chain ring, and then jammed in between the chain stay and the chain ring. It was quite difficult to get out.
Okay, I cleaned up everything, removing any gunk on the CR, the chain, the rear der wheels, etc.
Then I tried it again. Happened immediately. Once more a mess to get "unsucked."
Okay, I tried the middle and large and all was ok. But no luck with the small<>middle shift, kept jamming in there.
So, I took it to my friendly LBS mechanic. He checked it out and said it would have to go in the hospital for awhile while he figured out what was to him a somewhat perplexing problem. The small CR was not bent.
OK - he called last night. He has it fixed. He said there was too small a clearance between the small CR and the middle CR (he measured it with a device of some sort), and he put some spacers in and it is working fine. At my request, he also put a new chain in, as it was getting a bit worn (it doesn't take much for me to have a new chain installed). SO, I pick it up today.
I trust this LBS totally, and have done a lot of business with them, and they are excellent. However, when I asked the mechanic (who has worked on all my bikes) he could give no explanation as to why it worked fine Monday and not Tuesday!
To my knowledge, I did nothing unusual except to ride the trainer. He said there were no parts loose nor missing in the CR assembly.
So, I come to my wise friends in the 50+ forum to get their opinions as to what may have caused this seeming anomaly.