hydroplaning

[Huw Powell]

> I think it's the 'contact patch' thingie where the theory falls
> apart. With an aggressive tread, less of the rubber makes contact at
> the same pressures. Take the snow tire as an example. The contact
> patch is relatively small compared to a touring tire at the same
> pressure.

The "contact patch" is the rubber meeting the road, not the overall area
over which that takes place.  If a tire has 50% "grooves" and 50% 
"tread" it will use up twice the area on the road as a slick, in order 
to have the same "contact patch."

> With an aggressive tread, less rubber actually meets the road at the
> same tire pressures

Incorrect.

> If this is not true, why does every manufacturer have special designs
>  for wet road handling such as the Michelin HydroEdge?

We are talking about severe (unavoidable) hydroplaning here.  Cars can
have traction problems far below that speed, and also when the road is
only "wet."

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/