While my car is sitting, I am getting at all the nooks and crannies and cleaning them.
If you scroll back up to the last two pictures, I have a good guess why there.....If you remove the wheelwell plastic lining you will find a lip or a channel. If you don't (when you wash your car) spray full blast above and around the wheelwell, the dirt stays. Rememeber that for all your cars, hose your wheelwells thoroughly!
Anyways, I took some pictures of what I found, so far, BEHIND my plastic liner and you will never believe it. Till then, keep those hard to reach places clean!
Chris