I can tell you one thing, whatever the nuts are made of it isn't some miracle alloy that allows them to come off easily. All of my studs backed out from the head instead of the nuts coming off.

I tried clamping them in my vice and still no luck. Maybe some heat on the nut will help.

I've also made the decision to reuse the factory studs.

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1982 300SD
1992 190e 2.3 8v
2002 P38 Range Rover