tire size for 16x8

[mike86ttype]

I have centerlines 16x8 with 4.5inch backspacking. i am currently running 245/50/16 on the front and the tires bottom out and rub on the fender when i hit a hard bump. What a good size smaller tire to go with and also whats the biggest i can go on the back.

 

[Instro84]

i have 225's and 255's on mine.

 

[mike86ttype]

225/?/16 255/?/16 whats the middle number 50
GREAT I PUT THIS IN THE WRONG SECTION CAN MOD PLEASE MOVE. THANKS