what is the purpose of multiple types of bearings

so we see all of these different types of bearing out there on the market your basic Oreiley's pieces and then you have your trimetal with the steel backing and the copper center with lead face, but why so much emphasis on material selection like this when everything floats on a film of oil and never contacts (in ideal situations) the bearing to begin with?

Two things come to mind.

First a softer bearing will allow a piece of dirt or metal to embed in it minimizing damage to the crank, whereas a hard bearing will just keep the impurity grinding away between the crank/bearing until something wears down enough to allow it to exit.

Soft bearings usually are not as strong, potentially allowing them to deform under high loads & ultimately failing.

Essentially the material varies from soft at the crank to hard near the block or rod. The soft area will allow some wear & forgiveness if metal to metal contact occurs. The thickness of the soft part varies as to the design. More soft material gives longer wear on a regular motor, but decreases strength. The backing is designed to retain shape & bearing crush for positive retention. Layers in between are to promote adhesion of the dissimilar metals & to also help conduct heat.

This in only a small part of what is involved, but hopefully it helps.

You should also look at the King Alecular Pro Series bearings, since they have high imbedibility. The aluminum alloy lined bearings are also becoming very popular too.

Bret

do you have a site you could direct me to, I have never heard of those bearings before

i never knew bearing were so soft(some of them). i have some clevites in front of me that i can scratch with my fingernail and put a groove in it!