well, I probably should have looked at that before I mounted them....the readings seem to be fine though.......and Paul, sorry about that...I'm a bit lazy with commenting and stuff.....And aren't sonars a lot of money? Do they make cheap ones? And I'm going to end up buying longer ranged sensors to go along with these, probably mounted higher up--and the whole reason I posted on the forum was to make the algorithm better Paul!! 
Any ideas?