A strap forming assembly for a strapping machine includes a first forming wheel having a circumferential groove formed in a rim thereof and a second forming wheel cooperating with the first forming wheel and having a mating a circumferential crown extending therefrom. The first and second forming wheels cooperate to define a forming wheel nip therebetween. The forming wheel nip is non-planar. Strapping material fed into the forming wheel nip is permanently, longitudinally deformed.