the "break away" point at the top of these graphs is not a sudden loss of traction. The graphs I have seen are curves. Tires have an optimum slip angle (turning) and slip percentage (straightline). This angle or percentage is the top point on the graph. If you go beyond this point, it is not sudden death, it's just slower.
Think about accelerating from the starting line. You want some wheel spin, but not too much. If you try not to spin the tires at all (0% slip), you accelerate slowly. If you spin them too much, you go just as slow.(Same with braking - between lock-up and under-braking)
When turning in LFS, if you don't hear tire scrub, the tires are not at their optimum slip angle. If you are turning too hard or too fast, the tires will start screeching. They are not at their optimum slip angle and you will go slower.
Tires only have so much traction, and the when you exceed their maximum traction, they have less grip (not zero grip).
Wow, I wrote more than I wanted to. oh well. This is very complicated, especially when you factor in accelerating or braking while conering.
oh, one more thing, since we're talking about books, one book i recommend for everyone who likes driving and racing is "Going Faster! Mastering the Art of Race Driving". It's very informative and helpful. I've written too much already, so i'm not going to write a book review here, too. look it up on google. (This page lists all the chapters, etc.:
http://www.themotorbookstore.com/gofamaartofr.html)