it's usually a prefernence thing. The measurements that the last guy posted are probably stock specs from Fender which are just simply the median of tone. Usually you want your treble side closer than the bass side... but you don't want them too close... then the sound breaks up and you get what's called "natural distortion" Some people like that. But you never get a true clean tone. Some special case may also exist... If you have a floyd rose trem guitar you may have to leave them a little lower than you'd like to accomoate for the bottomed out trem placement.... So just turn your guitar volume up how you like it and play around with different heights... find what sounds best to you.