Originally Posted by
Camilo
My experience is similar. I've used 9 speed chains with 8,9 and 10 speed cranks and 8 and 9 speed cassettes. 8 speed crank-9 speed chain-9 speed cassette. 10 speed crank-9 speed chain-9 speed cassette. 10 speed crank-9 speed chain-8 speed cassette. And of course 9 speed crank-9 speed chain-9 speed cassette. On my 10 speed cassette, I only use 10 speed chain. But I'd also not hesitate to use a 10 speed chain on any of the above if I needed to (now that I think of it, I might be doing that right now.... I'll have to check.
They all shift fine. I think the rule of thumb is that any "higher" chain will work with any "lower" cassette, but not vice versa. The cassette spacing is set according to the width of the chain and a "lower" chain will be too thick and there won't be enough clearance between the sprockets. The inner spacing on all chains is the same, it's just the plate thickness - and therefore overall thickness - that gets thinner as you go up in "speeds". I don't think the cranks care at all about chains, or at least don't care within a generation (i.e. one up or down). The chainwheels don't care because all they feel is the inner width of the chain. Front shifting isn't as precise as rear shifting and therefore the overall width of the chain isn't as important.
Anyway, that's how I look at it.
Except that 8-speed chains work fine on 9 speed cassettes and chainrings, plus, they are cheaper, and they last longer than narrower chains, and my experience is, they shift at least as well as 9 speed or 10 speed chains do on 9 speed drivetrains. And if your chain is TOO much narrower than the gears it is supporting, it brings up another set of problems. In particular, it becomes especially problematic to shift a narrow chain on a triple - as it can drop between the chainrings rather than on them. This isn't an issue with a 10 speed chain on a 9 speed crank, but it can be on an 8 speed crank, and is DEFINITELY an issue with older cranks having 6-7 speed spacing.