Hi Frank,
Thats a good test alright. I suppse it's a given that the contact patch gets smaller at higher pressures but its surprising that you encountered a rounder patch. This happened below sidewall pressure right? Anyway, i was searching for info on contact patch size vs traction and found this:
www.stevemunden.com/friction.html
He is mostly talking about bike tires but also refers to car tires. I think it's conclusive enough evidence for me that traction doesn't decrease with higher pressures/ smaller contact patch. So, getting back to Brucepick's experiment, i'm looking forward to seeing how the real world results correlate to physics theory.
ollie