alig said:
Currently I have a CRX 3 (2008) with a Sora Triple FC-R453 50-39-30T Octalink. It is a 9 speed.
Can I swap the bottom bracket and crankset to a FC-5603 Hollowtech II Triple (even though it is a 10 speed?
If so can I also then change the 50T to a 52T chain ring at a later stage?
AFAIK, 'yes' to both questions ...
If you haven't observed a physical problem with your current Sora crank, then the true benefits from changing cranks will be almost entirely cosmetic -- personally, FWIW, I 'love' Shimano's Octalink BB and have just switched a couple of my bikes BACK to Octalink BBs & cranks ... with the external BB/crank combinations probably destined for some of my odder-and/or-older frames (e.g., an early-70s vintage Raleigh Grand Prix)!
Another option for you would be for you to upgrade the crank, itself, to an Ultegra 6503 crank OR simply a better Shimano OUTER chainring (the Ultegra & Dura Ace chainrings ARE better than the 105-and-below chainrings ... the 105 5600/5603 rings are probably
the same as on your SORA crankset except for the superficial finish) ... the 39t
inner chainrings (used on doubles) of the 105-and-below are functionally equivalent to the DA/Ultegra 39t chainrings ... for the 39t which is used as a middle chainring on a triple, there may be some difference in the ramping, but it probably doesn't matter as much the ramping-and-pinning on the outer (53t/52t/50t) chainring.
BTW. To state the obvious, when you change the outer chainring size, you will need to adjust the height of the front derailleur.
