ok...i have a triple road group and want to switch to a double....i have older (2003) tiagra 9 speed triple shifters and am wondering if i can put on a (2006) double truativ rouleu crankset (52/39) without having to buy new double shifters...also, i figured if i do upgrade the crankset ill need an external bearing bb to go with the truativ rouleu double crankset...is this conversion possible?