Moving from approved and tested treatments to experimental therapies on the Bike that Kills Front Derailleurs, I wondered if the 9-speed SRAM PC 951 chain might fit just loosely enough on the FSA chainring to get sideways and jam there. The ring was technically only for 10-speed systems, which is a bummer if you're one of the poor saps who bought in when 9-speed was state of the art. Would a 10-speed chain work on the cassette?
Yes it would. The 10-speed Connex chain I slapped on for a test shifted perfectly well on the 9-speed cassette. It also jammed on the chain ring at least as badly as the 9-speed chain I removed.
Okay, let's go the other way. Maybe the floppy, sloppy fit of an 8-speed chain would allow it to slide off the chainring without a hitch. But would it fit the 9-speed cassette?
The 8-speed chain shifted and ran almost perfectly on the cassette, but jammed on the chainring as badly as the other candidates. It was only sluggish shifting between one set of cogs on the cassette, requiring just a little extra nudge at the brifter.
Ten-speed cassettes are probably more finicky about chain width. And of course Shimano now has its asymmetrical chains and drive systems supposedly requiring them, in case you want to give them a tighter grasp on your cogs.
I'm sticking with 8-speed chains and friction shifting.