list:

essentially, thrust is inversely proportional to the "radius" from center
of axle to tire contact patch. the "flatter" the tire, the greater the
thrust for a given torque applied to the axle:

thrust = torque/"radius".

in other words, for a given engine/transmission, smaller radius tires
provide greater maximum thrust (until the tires slip, of course).

physically, the tire contact patch pushes back on the ground, which by
newton's 3rd law, "action = reaction",  pushes forward on the tire, hence
providing the forward thrust on the vehicle. it is the highway which
pushes the vehicle through the air!

dan

>So if the tire is underinflated the effect is that the last factor in the
>thrust value, the radius arm of the torque applied at the axle is less
>producing a slightly lower overall final drive ratio.  The reverse is true
>for fully inflated tires (larger axle to ground distance).
>