Originally Posted by
venturi95
Anyone tried this? I also want to use a 9 speed front derailleur.
You shouldn't have problems re-using those parts. You could re-use the 9s rear derailer as well.
Crank: 10s chain is a little narrower, so 10s chain rings are a little narrower. But 9s is pretty close and 9s chainrings usually work fine with 10s chain.
FD: The 9s FD cage will be a little wider than a 10s one. Shimano STI triple shifting is touchy, but I don't think the 9s FD would make it any worse.
RD: The shift indexing is completely controlled by the shifters, so a 9s RD can do 10s just fine. Shimano uses the same RD shift ratio across 8/9/10/11 speed.
You can re-use the 9s crank, FD, RD, and hub. You must get the 10s shifters, cassette, and chain.