OK, I've fixed the flakes, flattened out the bottom of the tire a little, bumped up the displacement map on the tire, fixed the edge loop in the back, and put a new material on the tire (which makes it look a little newer).

Here's some of the updated pics:

Pic 1
Pic 2
HD Pic 1
HD Pic 2

You can still access the old ones with the links above, so you can compare.

EDIT: Second HD pic is up.