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Re: Hydroplaning



On Fri, 05 Jun 1998 11:57:29 -0700, Gary Barry wrote:

>There has been some discussion of hydroplaning as related to tires.  The
>following is taken from a letter to the editor of USAA magazine (United
>Services Automobile Association), latest issue:
>
>"Hydroplaning starts when two conditions are met: The speed of the car
>is at least 9 times the square root of the tire pressure and the water
>depth is greater than the tread depth of the tire.  The design of the
>tread or the profile of the tire has little or nothing to do with
>resisting hydroplaning.  And once hydroplaning has started, it can
>persist well below the onset speed."

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.

DeWitt Harrison
Boulder, CO
88 5kcstq