Originally Posted by
70sSanO
...I know 8 speed chain works with 7 speed freewheel/cassette and 9 speed RD. I think you can even run a 9 speed chain with a 7 speed freewheel/cassette.
Yup. On my 2014 Diamondback Podium crabon fibber frame I'm running a mish-mash of stuff I grabbed out of the junk box. Currently (subject to change at whim or whenever I finish overhauling my 10-speed DA stuff):
- Ultegra 6700 crankset/chainrings (nominally 10-speed)
- Older Shimano 600/Ultegra 8-speed front and rear derailleurs
- MicroShift 7-speed brifters
- SunRace 7-speed 11-28 cassette
- Shimano HG53 9-speed chain
Until a week ago I had a KMC Z72 "8-speed" chain on that bike, but most nominally 8-speed chains seem to work with pretty much any 6, 7 or 8 speed setup, and even with some 9 and 10 speeds although tolerances may be less than optimal.
I'd been using that KMC Z72 chain on the bike for about a year and the only issue was occasional chain rub on the FD. Usually I could reduce it with the trimmer clickstops on the left brifter, or just change gears more appropriately. I left the chain a link longer than normal to avoid damaging the rear derailleur in case I got tired and careless on a climb and shifted into the 28T big cog while still in the 53T chainring. And I did that a couple of times. No problems, just a bit of slop in the chainline but nothing that hindered function.
That chain finally seemed a bit worn so I replaced it with a Shimano HG53 9-speed chain, one of two I bought from REI last summer when they were blowing out components cheap. I snagged a couple of HG53 chains for around $5, and three BB-UN55's in various common sizes for around $7 each. No idea why REI was doing that during the peak of the pandemic-related shortage of bike components, but what the heck. I didn't buy 'em all and left a few for other folks.
I should have installed that narrower HG53 chain to begin with last year. It works perfectly, no chain rub. Feels smoother shifting and riding. Less slop on the chainrings, which might prolong the life of the chainrings compared with the wider 6,7,8-speed chains.
I had to adjust the RD barrel adjuster very slightly, maybe 1/8 turn to quiet the clinking. The wider KMC 72 chain had enough slop to make it unnecessary to fine tune the RD so carefully.
And I've had a few more chain drops with the front derailleur, possibly because the MicroShift brifters are set up for 7-speed and I'm pushing that shifter beyond its intended use with this mish-mash Frankenbike.