aka: Dr. Cannondale
Join Date: Jul 2009
Bikes: I'd rather not count how many, thank you
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The old chainrings may shift OK, but 9-10 speed ones will be better due to the OD chain dimensions. You may also run into issues with the cage on the 8 speed RD being too wide to neatly manipulate the chain over the cogs.
My general rule of thumb is that Tricolor is awesome up to 8 speeds, but not so much beyond that (I've built about 20 bikes with 6400 series stuff). The crisper shift feel of components designed around 9 speeds and thinner chains is worth the price of entry, if you ask me. Even 5500/5600 105 components, which are dirt cheap these days, will outperform 6400 when you go beyond 8.
Others, of course, may disagree. Popcorn, anyone?
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