A spring for creating adjustable torsional resistance between two members which are pivotal relative to each other. The spring comprises a stack of axially aligned elastomer torsion rings (30). A locking ring (34) is secured to and separates adjacent torsion rings, one locking ring being associated with each torsion ring. The assembled stack is firmly attached to one of the pivotal members (14). There is connecting sleeve (46) engageable selectively with each locking ring and with the other relatively pivotal member. The number of torsion rings exposed to pivotal motion between the members to vary the torsional resistance of the spring is determined by engagement between the connecting sleeve and selected locking rings.