I thought the slight pull ratio change took place between 7800/6600/5600 and 7900/6700/5700?? I don't see any reason 9000/6800/5800 wouldn't work with one generation back...but it makes sense that they aren't quite ideally matched with two generations back.
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"The older you do get, the more rules they're gonna try to get you to follow. You just gotta keep livin', man, L-I-V-I-N." - Wooderson
'14 carbon Synapse - '12 CAAD 10 5 - '99 Gary Fisher Big Sur