Never use the cheap plugs that get installed from the outside of the tire.

The correct repair uses an inside patch that looks like a mushroom. The stem is attached to the patch, and gets pulled through the tire from the outside.

All of this applies only if the sidewall isn't cut, if the hole is not too close to the sidewall, and if there is no heat-related damage from having driven on the flat tire.

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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