Re: Hydroplaning

[Don Hoefer <hoefer@eng.pko.dec.com>]

Dewitt,

> Working this formula in reverse, if I want to travel 100 mph without
> hydroplaning, all I have to do is inflate my tires to (100/9)^2 = 123.5psi. 
:-)
> Seriously, I'm curious why inflation pressure is the primary factor.

Tire pressure determines the downward force that is exerted on the water.
You need this force to accelerate and move the water out of the way.

An analogy:     A water skier has to go a lot faster to ski barefoot than
                is nessecary when using skis.  Skies spread the weight
                (downward force) over a larger area allowing more water
                to support him.

To drive in the rain without hydroplaning you need a small tire contact
patch (high pressure, high force per unit area) and low speed.

Don Hoefer
'82 Coupe

Massachusetts, USA