I have no problem with a plugged tire, and repaired a runflat on the Z4 that way.

However, I would not rely on a plug that was applied from the outside. It is a risky repair. The approved method for repairing a runflat (and the safe way to repair a non RFT) is from the inside. The plugs look like a mushroom, and combine a plug with an inside patch.

My tire dealer had the manufacturer's instructions for my specific tire, I think they were Bridgestone. Different rules from each RFT manufacturer, so YMMV.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue