hydroplaning

[Huw Powell]

Dan Masi wrote:
> 
> > > Drive your car over a lift, put gauges on the tires, and
> > > observe the pressure.  Now operate the lift enough that it
> > > takes just some of the car's weight.  What did the pressure
> > > do?  Ok... now take even more of the car's weight on the
> > > lift.  What's the pressure doing?  Ok... now take enough
> > > weight on the lift so that the tires are just brushing the
> > > pavement.  Zero psi???  'course not.
> >
> > dum de dum... that's because some of the weight is being held
> > up by the
> > lift?!
> 
> Oh.  So, at what point does the tire pressure suddenly stop
> being related to contact patch area and load, then? 

Never.  say half the weight is on the lift - the contact patch will be
halved for the same pressure.

when the car is in the air, what is the weight on the tires? 0 lbs. 
what is the contact patch? 0 sq. in.

-- 
Huw Powell

http://www.humanspeakers.com

http://www.humanthoughts.org