Just out of curiosity, can tread wear affect alignment results? I never paid attention to the guys doing my alignments in the past, are the tires on the ground or is it done with the car raised up by the jack points with the suspension hanging? If its done with the tires on the ground it would make sense that tread wear could affect it right? Opinions?

 

we have 2 different alignment racks at school... one is done jacked up while the other is done with the car down on the rack... on fwd's i prefer the rack where the car isnt jacked up... reason being fwd cars usually call for a small amount of negative camber... from what ive seen if the car is aligned with the wheels in the air the camber will be fine but once lowered off the jack the car is going to go slightly more negative due to the weight... if its done directly on the rack you can set the camber with all the weight of the car on the ground... i think rwd's would benefit from being jacked up as they usually call for slighty positive camber... i dont really think treadwear would affect the outcome but i know for a fact that air pressure and any added weight that you may be carrying in your car will affect your readings... those racks will go nuts if you barely nudge the car... hope this helped some

 

Thanks for the input, I just figured that if you have bad negative camber up front (like 3-4deg) and wore the insides out that it would make it worse (4-5 etc) and then if this would affect a new alignment while still using the same tires. I think that it probably depends on how much the person doing the aligment cares about giving you the right alignment. Thanks.