Bicycle Mechanics - 8spd-9spd Chain Confusion

OK-This shouldn't be this confusing. But, I bought a DA group without chain that is a combination of 8spd & 9spd. 7400 8spd derailer & cassette with 7700 Octalink crank. I go to the LBS for a chain and they say it's either a 6,7,8 spd chain or a 9,10 spd. I say, "No, the previous owner assured me that these things work together". So, what's the difference between the 8spd cassette and the 9spd crank?

IIRC, chains come in 4 speeds: single, 5/6/7/8-speed, 9-speed, and 10-speed. The difference is the width of the chain, which also affects durability and what cassettes, derailleurs, and chain rings it will work with.

IIRC, chains come in 4 speeds: single, 5/6/7/8-speed, 9-speed, and 10-speed. The difference is the width of the chain, which also affects durability and what cassettes, derailleurs, and chain rings it will work with.

Ya, I get that. But is it just a matter of the width or the length? If you go to your local bike shop, the chains are grouped as either 6,7,8 speed or 9,10 speed. I understand that they had to narrow the width of the chain in order to fit more cogs so an 8spd chain is too beefy for a 9,10 spd cassette. But would a narrow chain work on an 8spd cassette?

But would a narrow chain work on an 8spd cassette?
I don't think that's a problem. If you do run into a problem, it's the reverse - smaller chain with wider pitch chainrings. I'm told that the smaller chains can dump into the gap between chainrings when downshifting the FD. But in your case, there aren't gaps between cogs in the cassette, so you're OK. You'll just be buying a slightly slimmer, more expensive, arguably less durable chain.

If you are using an 8sp. cassette use an 8sp chain. The front won't be a big problem.

Sorry to nit-pick terminology, but all modern chains have the same "pitch" (1/2"): http://sheldonbrown.com/gloss_p.html#pitch

Match the cassette to the chain and don't worry much about the chainrings. Also, it's best to match the front derailleur to the chain for best shifting and avoiding rubbing.

If you are using an 8sp. cassette use an 8sp chain. The front won't be a big problem.

+1

Shimano recommends that you do not use their 9s chain w/8s components.

Ya, I get that. But is it just a matter of the width or the length?
Width. (Of the outside only - insides are the same.)

Length must be custom-fit to each bike. Do you know how to do that?

+1

Shimano recommends that you do not use their 9s chain w/8s components.

Shimano also likes to sell chains. Just sayin'...

Width. (Of the outside only - insides are the same.)

Length must be custom-fit to each bike. Do you know how to do that?

I actually started another thread asking that question. The first response was that this topic comes up every 2-3 days. I'm not surprised. There seems to be 2 methods. The big ring-big cog +1 link method, or the small ring-small cog through the RD method which seems much more mysterious to me.

Shimano also likes to sell chains. Just sayin'...

yes, but the 8s chains are cheaper. Just sayin' :)

FWIW, I'm running a KMC 9 speed "Z" chain on my Shimano 600 tri-color 7 speed components...and it couldn't be smoother.

-Jeremy

I actually started another thread asking that question. The first response was that this topic comes up every 2-3 days. I'm not surprised. There seems to be 2 methods. The big ring-big cog +1 link method, or the small ring-small cog through the RD method which seems much more mysterious to me.

The small-small/RD method is clearly illustrated in the Shimano installation procedures that recommend it.

Have you checked out this thread (http://www.bikeforums.net/showthread.php?t=338432)?

Just installed an HG-93 (nine speed) chain to replace an HG-70 (eight speed), running with Ultegra SL derailleurs and an HG-90 (eight speed cassette). The shifting actually seems better, almost disconcerting in that shifts often occur with no noise (except for the click of the lever).

Biggest improvement is that the chain no longer rubs on the derailleur guides or jockey wheel housing, meaning that no trimming is required on the front anymore for any reasonable sprocket/chainwheel combination.