currently have 205/45/16 on all 4 rims, but i need to replace 2 rear tires. Friend has a 2 205/55/16 tires to sell me. Was wondering if i would run into any problems mounting them in the rears? like fender rubs, abs braking problems, etc?

 

205/55R16 is the stock tire size so there shouldn't be any fitment issues but your car will look very strange with the 205/45's in the front

 

I have the 2003 si which I think are 15 rims. These are aftermarket rims. A guy said it's possible that the smaller size in the front will cause braking issue since it has abs brakes. I didn't want to replace all 4 because they all have good tread. One tire has a bad side wall and the other has a small tear.

 

I think the guys is right about the ABS issues. If you never panic stop you will not notice a difference. You can also disable you ABS. Of course I think these are all bad ideas and you should just get a match set of four tires.