i heard of using washers to get rid of minor butterfly. can someone explain this to me?

 

Only in the rear. If you look at the top of the trailing arm, there's a small arm that attaches to the inner fender with 2 bolts (usually called a dogbone). If you remove the upper bolts, replace them with longer ones and place some washers between the dogbone and body mount, it will push the top of the tire out (add positive camber). It's not an exact science and you'll need to get an alignment to check it and maybe adjust the number of washers. I would also recommend you check and retorque the bolts after the first 100-500 miles or so.

Toe (tires point in or out rather than straight ahead) can also seriously affect tire wear if you've lowered your car and haven't gotten an alignment. Thhis is adjustable from the factory, front and rear.

 

It's like 1-2 washers for every inch you are dropped. Do not use more than 2 on the stock bolts. If you need to use more than 2 then you need longer bolts.