Originally Posted by pinky
Ran 10s on both my bikes this season. No worse than the 9 stuff, and I was talking to at least one bike designer who was saying they've had better luck with 10 because the narrower chains were shedding mud easier than the 9 stuff. Personal experience was that they survived the mud of New Gloucester and the snow of Gloucester and Nats.
Seems like the difference between 9 and 10 is like vanilla and chocolate. I dont know that there is a definitive answer as to which is better for cross. I ran 9 this past season (Ultegra, Dura Ace) and never had any problems. I think the main complaint with 10 is that the chains are thin -- and therefore more prone to breaking. I cant say that I've heard that 10 is better for shedding mud though -- when its muddy its muddy, and 9 or 10, your drive train is gonna get gunked up no matter what. Honestly I think that both 9 and 10 are somewhat un-necessary for cross. I never use all those gears, which is why I'm considering switching to single rings next year.
Frankly, whether u are using 9 or 10, i think your best protection against drive train malfunctions is having your stuff tuned right, and using a good lube.