why do tyres get flattened when in contact with the ground?

Question

anonymous · Answer

when the weight fals on the tyres the try to come in contact with the road so they get flattened.....

anonymous · Answer

http://en.wikipedia.org/wiki/Flat_tire

anonymous · Answer

Gravity is applying a force pulling down on the car. As the car is not moving down, there is an equal and opposite force pushing up such that the two forces are in balance. The forces are acting through the tyre from the ground. The tyre deforms which has two consequences. 
1) the deformation of the rubber requires a force. 
2) the volume inside the tyre changes which increases the air pressure within the tyre. 
When the forces required to deform the rubber and increase the air pressure are equal to the gravitational force, the balance of forces is established and the system is in equilibrium. Applying more weight to the car will result in more deformation and increased tyre pressure until a new balance is achieved.

anonymous · Answer

for attaining a state of lowest possible pressure application on them they tend to increase the surface area on which the gravity is being applied. hence for lowering the pressure on the tires the increase there surface are by getting as flat as possible

anonymous · Answer

Thanks all of you for your response!All of 'em helped me equally.