New rims alloy some times compress under the lugnuts after some driving. I've personnaly torqued a new set of wheels on a customers car and had them drive 25-30 miles to heat of the rotor and rim little, and seen the nuts need over a half turn to be to the same torque with the same torque wrench. Sears even has all kinds of disclaimers about alloy rims on thier workorders. Everytime I pull a wheel , alloy, off one of my cars and put it back I drive 25-30 and retorque it.