The only concern that I have with the sealant kits is that users may decide that they constitute a repair, and continue to drive on them. Bad plan.

As a belt and braces approach, I understand carrying either a sealant kit or a portable 12 v compressor. A compressor by itself would be an alternative to the sealant, unless it is a very fast leak.

My back up to the runflats is a cell phone. Back before the advent of cell phones, I never carried two spare tires except for extended off road trips.

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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