the correct term for this is 'nibbling'. It comes from using wider tires and/or negative camber. Reason: as a tire is leaned to one side(camber) it will pull that way. Usually when stock width tires are switched in favor of wider ones it accentuates the neg. camber of the car. hence both tires want to drive toward eachother and depending on the angle of the road beneath each tire, it will try to go that way.