Since this is a racing bike, for someone 5'-10", I would think at least a 56 - 57 top tube would in order. It was recently published that Peter Sagan (I think he's a racer) At 5- 10' - recently went from racing on a Cannondale with an 58cm extra long top tube, to a Specialized , with a stock 56 top tube. The only way he could make it work for him, was to use a massively long 140 stem.