Subject: How does a nail puncture a tire?

I am at a loss to understand how a nail punctures a tire.  It seems improbable 
that a nail will be standing on end unless by statistical chance (having been 
perturbed by a previously passing automobile).  If lying flat on the surface, 
what are the mechanics that cause the nail to move to a position of pointed-end 
up?  I recently enjoyed two nails in the same tire, and I am sure it was not 
vandalism (one was positioned under the "footprint" of the tire).  The 
statistical likelihood of two nails balanced with pointed end up is small, 
thus, there must be a mechanical movement when the tire first touches the nail 
that results in the puncture.  What is it?

James Selevan, M.D., BS Electrical Engineering and Physics

Re: How does a nail puncture a tire?