hydroplaning

[Orin Eman]

> How does all this relate to hydroplaning?  If the water is around as
> deep as the tread (probably a factor of roughly 3 or so?????) then
> tread can help channel water out of the way, letting the rubber
> contact the pavement.  Here a more aggressive tread will help, since
> the water is under higher pressure between the knobs and the pavement
> and will thus "get out of the way" faster, and has somewhere to get
> out of the way _to_.  I don't know how deep the FAA's puddle is, but
> if they hydroplane at a speed that depends only on the tire pressure,
> then it is probably quite a bit deeper than the tread depth.

You aren't going to be able to measure the depth of a puddle ahead
of you on a runway or the road so the depth of a test puddle isn't that
interesting as long as hydroplaning occurs at some speed...

You have to assume that puddle ahead of you is deep enough and
adjust your speed accordingly.  The FAA rule of thumb works well
enough - at typical tire pressures and freeway speeds, you can
hydroplane if the puddle is deep enough and that has been my experience.

Orin.