I am also wondering what kind of a difference I would see by going to a smoother tred tire that can hand a little more air pressure that my current stock tires. Will this make some difference in terms of speed. for what its worth I am riding on 700-40C tires that are somewhat knobby and I see that giant makes a smoother tire that is still the 700-40c size but can also hold 10 PSI more air which I am thinking would cut down some of my rolling resistance.