[longassname]

Tri-metal bearings were pretty much industry standard for a long time. They are made through a plating process where a very thin surface of babbit material (lead alloy) is plated onto copper which is on a steel backing. The main "bad" thing about them is that the layer of babbit material is extremely thin so any contamination can quickly tear through it. The other bad thing is that if something goes wrong and things get hot they have a lower melting point of about 400F.

The high silicon aluminum bearings have been replacing the tri-metal bearings. That's part of why you see 200,000 and 300,000 mile warranties now as the oem's have switched to them. They have a very thick high silicon aluminum surface which doesn't imbed contamination and can't be torn through, they pretty much don't wear, and they have a 1100F melting point so if something goes wrong and you have an oil film breakdown they aren't nearly as quick to get toasted.