Pardon me, but what does that quote about peeling vs sliding friction have to do with the mud caked around your fenders and tires? I mean, I guess with all that mud stuck to you you're trying to "shear" mud instead of rolling over it, but at that point you probably aren't going very fast anyway because you've completely lost control.

When you say street tires you mean slick treads right? Seems like a bad decision for mud - you'll cut right to the bottom of it start sliding around all over the place. Put some knobby tires on, the fatter the better, and try that muddy section again.