May I ask if a 16" space saver will fit a 2.5Si with M Sport, it is as original. I bought a 17" one whose overall diameter is 18". I want to be able to put the 16" space saver with the tyre deflated in the front passenger footwell of my 2007 N52, in a cover, so I can tour with or without a passenger. The 18" with tyre would only fit at a very awkward angle filling the cabin passenger area! Otherwise I guess I'll have to think again. Mount on boot?!