I have a set of 8 speed bar end shifters (SL-BS64) and several 8 speed cassettes.....11-30, 12-25, 13-26 and similar. The single chain ring is a FSA 9/10 speed 44t.

I also have a 105 rear derailleur (RD-5700) that I'm thinking about installing, Shimano specs show it would work with a 30t cog.

I have a new 9 speed chain, I was wondering if that would work or do I need to get something else.

Thanks!!!

Count "Speeds" , the number of cogs on the back hub , if 9 you need a 9 speed chain..
... pretty straightforward ..

You'll need an 8-speed chain. Everything else should play well together.

You don't "need" an 8-speed chain, just nothing wider. A 9-speed chain will work fine on an 8-speed cassette. However, the 5700 is a 10-speed rear derailleur and may, in fact, have too narrow a cage for an 8-speed chain so a 9-speed, or even 10-speed chain may be required.

+1, a 9s chain works fine for 8s or 7s. It's slightly narrower than necessary, but it won't be an issue.

Just about the only way it could (rarely) become a problem is if you have fairly wide chainring spacing, and the narrower chain hangs between the tips of the inner ring's teeth and the face of the outer. But this is far more common when using a 10s chain for 9s, than a 9s for 8s since most cranksets have the same chainring separation for 8s and 9s.

That's what I was hoping for. I thought that the major difference between 8 and 9 speed cassettes in the spacers (other than the extra cog). My main concern was the 9 chain fitting thru a 10 speed derailleur.

If I need to get a 10sp chain, so be it. I'll just try what I have first to see how it works.

FB---I've got a single speed crankset with a multi crankset gear so hopefully I can run a good 1X8. It's spaced nice, right between the 4th and 5th rear gears. If everyone plays nice together I'll have eight speeds. If either end of the range pitches a fit I'll just limit it out of the game.


Thanks.

A 9s chain will run fine through a 10s derailleur. The difference in width isn't enough to cause rubbing on the cage, except maybe at the tip of the lower cage where the chain comes from the chainring. It's possible (but not likely) that the chain may rub a bit when coming from the extreme angles, (innermost and outermost sprockets). If that's a problem it's easily fixed by filing a bit off the inside of the cage there to make sort of a funnel and clear the chain.

Good deal. It seems as if I'm good to go.

Most Shimano RDs are designed to work with chains 1 size wider. https://www.shimano.com/publish/conte...ty%20Chart.pdf