HMB, I suspect the S500 wheels would use a larger diameter lug bolt because it's a heavier automobile than the 380SL. Another important feature is the offset of the wheels. That is indicated in mm by the ET dimension stamped on the back of genuine MB wheels. Recommend calling the Parts Department of your local MB dealer and asking if the S500 wheels are compatible with your 380SL. If the lug bolts are, by chance, the same diameter verify that the S500 lug bolts are also the same length. Shorter lug bolts will lack the necessary thread engagement, whereas longer lug bolts may create interference problems with the emergency brake components inside the rear drums.

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Fred Hoelzle