What causes tire wear on the outside edge? Well if the tire worn out on the outside edge this means that the car have alignment problem.
It is unusual for the tire to wear only on the outside, this is obviously a problem on the positive camber alignment problem. Camber adjustment is the adjustment on the tilting of the wheel it can either be a negative camber or a positive camber. Since the tire abnormally worn on the outside edge then the problem is the positive camber alignment, positive camber is the tilting of the wheel away from the car frame. Likewise if the problem is the tire wear on the inside edge the problem is the negative camber alignment.
Possible cause of tire wear on the outside edgePositive camber wheel alignment