Hello,
Basically what happened is the wheel and hub corroded together. What you need to do is very carefully take a hammer to the back side of the rim and hit the rim. Just becarefull not to knock the car off of the jack or you can try hit the tire from the front.Once the tire is off of the car take some sand paper or a wire brush and clean the hub. Once you have cleaned it take some grease and put it around the hub where the rim sits.
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Thanks Ryan K
Volvo Master Technician
15 years working on Volvo,Saab,and VW. ASE Master,Volvo Master.Freon recovery certified.