[Land-speed] Contact patch size

[Skip Higginbotham]

Elon,

Please explain to me how patch size "obviously" varies with surface 
medium. I assume here that you are not talking about mud. We don't 
run on mud, snow or sand.

Also, when most of us talk about pressure and it's effects, we assume 
that the tire is designed for the actual load, high speed (200+) and 
high pressure (75 psi+).

I do know that at Bonneville, lower tire pressures permit flex and 
heat generation and in so doing, use up horsepower. An increase in 
tire pressure reduces heat and HP loss (reduces patch size) and 
usually increases speed. Traction is also usually increased due to 
higher patch pressure (the reason that drag slicks/other wide tires 
are not effective).

Skip



At 01:23 PM 11/17/2008, Elon wrote:
>It can't be as simple as that. I'm not an engineer but it has to do with the
>way load members reacting to a force. My guess tire construction has more to
>do with it. Radial vs. bias ply geometry distributes load differently.
>Nylon, Kevlar, steel fibers, all react to stress in a different way. Then
>you are forgetting surface. Take the identical tire and pressure and place
>it on sand, concrete, and snow. Obviously, the patch size will vary with the
>surface medium. You did say 'patch' and that means the amount of surface in
>contact. So 'function' is not as simple as pressure in my book. -Elon
>
>
>
>From: Jon Wennerberg
>
>That is, the contact patch -- the number of square inches of tire
>
>that's contacting the ground -- would be a function of tire pressure
>
>and the weight that's on those square inches.
>_______________________________________________