quattro Digest, Vol 7, Issue 97

[Larry C Leung]

Tire pressure is inversely proportional to contact patch area.
No difference on tire size/profile. Wider tires just reshape the
contact patch to a wider, but shorter front to back patch. 
So, as pressures rise, contact patch gets smaller, hydroplaning
reduces, because pressure of the remaining patch increases. 

LL - NY


> Date: Thu, 27 May 2004 07:01:49 -0700 (PDT)
> From: Richard Tanimura <rictan302 at yahoo.com>
> Subject: Re: hydroplaning
> To: Mike Arman <armanmik at earthlink.net>, quattro at audifans.com
> Message-ID: <20040527140149.37380.qmail at web21325.mail.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
> 
> 
> --- Mike Arman <armanmik at earthlink.net> wrote:
> 
> > Hydroplane speed is 9 times the square root of the
> > tire pressure.
> 
> That is the darndest relationship. I am trying to
> figure why it would be so. Or rather why a lot of
> other factors like patch size or tire width don't
> factor into it.
> 
> True aquaplaning story: My old Volvo had been rear
> ended. The damage looked to be very slight but
> apparently the rear axel was out of alignment. I ran
> through a big puddle on the highway and my back end
> stepped out on me and I did a 360 before I could stop
> the car. On the way home at much lower speeds, I could
> feel the back end pull every time I hit water. The
> rear wheels were acting like rudders pointing slightly
> in one direction. I will never again take a small rear
> end collision lightly.
> 
> My Quattro has excellent rain manners. There is
> nothing like it in the rain.
> 
> Rich
>