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Lots of possibilities. Failing bearing, uneven tire wear, alignment problems, tire pickup, failed drop link or A-arm bushings, failed strut. You can check your bearing simply grabbing the tire and giving a yank left or right. You should not hear a clunk or feel any play in the wheel. Other suspension components are best checked on a lift where you can get a good look.

Brad Roberts is our local suspension Guru. He probably forgot more about Porsche suspension then I will ever know. Perhaps he will chime in.