Very interesting.
"In the Imperial system, the equation is 9 times the square root of the tyre pressure. So, if your tyres are at 25 psi, if you drive into a puddle that is deeper than your tread depth, you will aquaplane at 45 mph (72 km/h), whereas if your tyre pressure was 36psi, you would aquaplane at 54 mph (87 km/h). The advantages are obvious."
Is aquaplaning that direct a calculation? This seems almost unbelievable to me, considering that some tread pattens are much more adept at displacing standing water than other tread patterns. That calculation above ONLY takes into account tread depth, and not tread pattern (or perhaps displacement abilities measured in "mm of H2O per metre")
Also, in that conclusion from the quote above, he (Julian Edgar?) only lists the factors that DON'T affect tyre "grip", and he never answers the question he poses in the first sentance of that conclusion.