There is no oil pressure at the bearings, the pressure drop or restriction occurs before the load bearing portion of the bearing.

I posted this explination earlier and it seems prevalent so I will post it again:

"Let me start by saying that if you go to a tribology website, there will be no category of bearing wear that has to do with low oil pressure, only lack of lubrication. The oil pressure isn't what supports the crankshaft. When a cylinder fires, you have maybe 600-900 psi acting on piston with a surface area of 13 sq inches and it's being supported by a main bearing with a supported surface area of maybe 3 sq inches? The force on the piston creates a downward force of 8000-12000 lbs while the upwards force 30 psi of oil pressure in the crank journal might be only 90 lbs (it's actually 0 because the oil pressure acts on all sides of the crank, therefore, cancelling itself out). The oil pressure generated by the pump has no contribution to the bearings ability to carry a load, it only ensures that there is more than sufficient oil supply to the bearing. Instead, think of a car hydroplaning. The way a wheel makes contact with the road forms a sort of a wedge infront of the contact patch. If you push that wheel through water at high speed, water gets packed into that wedge, creating tremendous pressure on the wheel. That pressure can actually lift the car off the road and that is when you have lubrication. Inside of your engine, that same wedge forms between the bottom of the crank journal and the bearing shell. As the crank rotates, friction between the crank and the oil pulls the oil down into the wedge much like water is packed infront of the wheel, pressure is generated, the crank is lifted off of the bearing, and lubrication is achieved."

Remember, I am an engineering student and not an engineer. I have taken no tribology classes. This is how I believe it to work and I might be wrong so do discuss what I say and don't take it for granted.