I drive 75 miles each way to work and 95% is on open highway 65 to 75 mph. I am thinking of either going from 16 tooth sprocket on front to 17 tooth or possibly going from 42 tooth rear to a 40. Any one have experience changing the gear ratios on the 500 or suggestions. I'm at 29,000 miles on my '08 and it wont be too long before I have to change out sprockets, and chain. Any reccomended business to deal with/ or name parts to use?