Tire Issues - Why?

[Racer Boy]

Those tires aren't "chunking", they are just worn out. Chunking normally occurs when there is thick tread, the tire overheats, and literally, chunks of rubber separate from the tire. That is one reason why most track tires have very little tread, or people get their tires shaved for track use.

Your tires just wore down through the outer layer of rubber, the base layer is exposed, and then the tread layer quickly starts wearing away exactly like is shown in your pictures. In no time at all you will wear through the base layer, and you'll see the cords showing. Once the tires are at the condition shown in the pictures, they are done-for, and are no longer safe. You can get more life out of your tires if swap them on the rims side-to-side, so that when the outside edge gets worn, you dismount and then remount them on the rim the other way, so that the worn part of the tire will now be on the inside edge.

As others have said, you need more negative camber to keep this from happening. You can also alter your driving style to try and minimize this happening, but there is only so much you can compensate for.