The Z4 does not have as spare tire. Run flat tires are used.
It is in the Owner's Manual.
I only fond a BMW z4 with a towbar in the Netherlands I saw the car and the towbar. The brand of the towbar is Westfalia. The car is for sell on www.autowalinga. nl
The 2013 BMW Z4 has 16 valves.
The 2006 BMW Z4 has 24 valves.
The 2007 BMW Z4 has 24 valves.
The 2012 BMW Z4 has 16 valves.
The 2005 BMW Z4 has 24 valves.
The 2009 BMW Z4 has 24 valves.
The 2008 BMW Z4 has 24 valves.
The 2011 BMW Z4 has 24 valves.
The 2010 BMW Z4 has 24 valves.