Get a suction cup of some sort. Like the kind that is typically attached to the baskets that mount in the shower (or even better, one of those GPS windshield mount suction cups that has a lever). Wet it a little, press firmly on the center cap and pull. Should do the trick. The bigger suction cup the better. The cap diameter is 68mm according to BMW's spec. Also realize there are 2 styles of center caps now, both 68mm diameter. The old cap on the left is P/N 36 13 6 768 640 and came on all the E53 X5's. The new cap on the right (has a chrome outer ring and is convex) is P/N 36 13 6 783 536 and came on all the E70 X5's. Some BMW parts sources classify the old one as being superseded with the new one, but if you prefer the look of the old one you should still be able to pick it up without too much problem.

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