Here is what I was told about coker...

Coker uses old tire molds to make their tires that are outdated. For example: Their tire may be based on a BF Goodrich Radial TA but it is an old out dated mold that they purchased.

Diamond back uses new molds and pays a per tire fee to do so.

This is based on what I heard nothing more. My uncle buys a lot of tires from Coker and he is very happy with them for his big white walls that he buys.