whats the perfect offset
 

I have a 99 accord lx sedan and im getting some xxr 521 17x7. I just want to get a good fitment when i lower my car. lmk asap. Im new to this and trying to learn

that depends on what kind of fitment your looking for stanced,flush,hellaflush,poke,euro poke,sunk,staggerd ???. you can start your learning here http://honda-tech.com/showthread.php?t=2077445