I just got some new wheels, but I haven't picked out the tires yet because I don't have much knowledge about the recommended size. The fronts are 17X7 and the rears are 17X9. Any suggestions?

depending on the brand, you can ususally get away with 215/50r17s(front) and a 255/55r17 (rear)
different brands offer slightly larger contact patches than others.

Factory is 225/50-16...on 7" wide ....so 225 will fit fine. I run 245/50-16 on 7" wides with NO problem. 9" will handle some Fat boys !!
On 17", use a 45 tire to keep the speedo accurate, and not loose any torque at the bottom end.