Load share – tyre & air?

There are two wonderful inventions – amongst many others – in the pneumatic tyre and the rolling element bearing. But sticking with the former, what is the load path thru the pneumatic tyre and wheel from the tyre pad to the vehicle? What load share is on the tyre and how much on the pressurised air in that tyre?

So looking at the healthy, inflated Michelin tyre in the top image, & that unhappy deflated tyre in the lower image, the tyre has very little stiffness to carry the vertical load. So the load is virtually all on the air, as the tyre itself cannot carry any useful load.

So in trying to track the load and the load path, from the tyre pad, where the load is easy to measure on a scale, how does the load get up onto the vehicle?

Well, the air pressure is increased by the compression of the load on the tyre. So this pressure increases and transfers the load onto the wheel, then onto the suspension, then onto the spring & vehicle.

But the air inside the tyre is static & the pressure acts equally all around the inner rim of the wheel. So the upward load from the air to the wheel rim is…zero! No, the load is ALL transferred via the tyre from the ground onto the wheel. It uses the air to pre-load the tension in the tyre, and the slight changes in shape of the tyre around the tyre pad lead to the transfer of the load from ground to wheel.