I ride 48x16 on the almost completely flat roads of Champaign, IL. I rode on the 9th out of 10th gear on my old Raleigh, however, and just chose the gearing that made sense compared to that. It's almost impossible to tell you what gear to choose for your legs, but you should be able to grow into almost any gear with time as you will gain strength with riding. That being said, 48x16 seems to be at the higher end of what most people ride on the street simply due to the difficulty of starting from stoplights and such on steeper gearings.