Originally Posted by
musterion
So, by inference, the 50t big ring would not have much of a difference, but the middle is more significant. I've got a 9 speed in the back--how does this help or hurt?
There is also a difference in synchronization but I think that is not a big problem. The 9-speed cassette is not an issue, the chain width may be an issue. The 9-speed chain is wider, the 10-speed front derailleur is probably a bit narrower than the 9-speed FD.
Since you already have the 10-speed triple FD, why not try it. If you have problems you could try a new 10-speed chain, I think it would work OK with the old cassette and crankset. But try the old cassette, chain, and crankset first.