I just got a 1998 Chevy blazer 4x4 well the passager wheel is 3 to 4 inch passed the fender where all the other wheels are flush why would that be? and when i get up to 30 mph the (passage side around the wheel) starts to knocking the faster u get the loud it gets, what would cause this?

 

it sounds like your CV axle is poking out on that side.... 4" is an awful damn lot though....

You can park on a level surface and turn the wheel all the way to the right.
poke your head under there behind the passenger front tire. (take a flash light)
follow the shaft that pokes out of the back of your wheel to the center of vehicle. when you see the black rubber boot, does the area behind it look like there is a lot of grease/oil splashed around? Does it look like the shaft has backed out of the differential housing (where the shaft pokes into the box it looks like it's headed to/inserted into)?