Are really types in this subculure, bikers, rockers, ... so much predominately SP? What is your experience?

I have friends in this subculture but we are more at the edge of it and not really mainstream bikers (i have more than 2 jackets ), and i think types are predominately Ns, and SPs. Well, mostly 7s. But my INFJ 9 friend is biker (she) so i really dont see so much stereotype as they portray this groups as only SP.