So far, we've mostly talked about torsion classes for Dynkin quivers, which give the Tamari lattice and other Cambrian lattices. This week, we will talk about torsion classes for preprojective algebras, which give the weak order on Coxeter groups of types A, D, and E. As usual, we will do many examples using the symmetric group, where the stability fan turns out to be the braid arrangement.