Suspension system with dual rate torsion bar

1. A dual rate torsion bar, comprising:

a first rate torsion bar section having a proximal end with a first external spline and a distal end with a cylindrical pin-shaped engagement cam extending through and protruding from an aperture in the distal end of the first rate torsion bar section;

a second rate torsion bar section extending from the distal end of the first rate torsion bar section and having a distal end with a second external spline;

a first bracket having an interior spline engaging the second external spline of the second rate torsion bar section, the first bracket configured to be mounted to a vehicle structure;

a second bracket having a cam bushing receiving the engagement cam, the second bracket configured to be mounted to the vehicle structure, wherein the engagement cam is rotatable within the cam bushing and the cam bushing includes a stop surface for preventing rotatable movement of the engagement cam beyond a predetermined position; and

a control arm mounted to the first external spline of the first rate torsion bar section.

2. The dual rate torsion bar according to claim 1 , wherein the second torsion bar bracket includes a pair of bushings on opposite sides of the cam bushing.

3. The dual rate torsion bar according to claim 1 , wherein the first rate torsion bar section has a different spring rate than the second rate torsion bar section.

4. The dual rate torsion bar according to claim 1 , wherein the first rate torsion bar section is longer than the second rate torsion bar section.

5. A nested torsion bar, comprising:

a first rate torsion bar having a proximal end with a first outer spline and a distal end with a second outer spline;

a second rate torsion bar having a distal end with an inner spline connected to the second outer spline of the first rate torsion bar and including a proximal end with a third outer spline;

a first torsion bar bracket having a splined aperture for receiving the third outer spline of the second rate torsion bar, the first torsion bar bracket configured to be mounted to a vehicle structure;

a second torsion bar bracket configured to be mounted to the vehicle structure and receiving the distal end of the second rate torsion bar; and

a control arm mounted to the first outer spline of the first rate torsion bar;

wherein the distal end of the second rate torsion bar includes an engagement cam and the second torsion bar bracket includes a cam bushing receiving the engagement cam of the second rate torsion bar; and

wherein the engagement cam is rotatable within the cam bushing and the cam bushing includes a stop surface for preventing rotatable movement of the engagement cam beyond a predetermined position.

6. The nested torsion bar according to claim 5 , wherein the first rate torsion bar has a different spring rate than the second rate torsion bar.

7. The nested torsion bar according to claim 5 , wherein the first rate torsion bar includes a rubber bushing mounted thereto and disposed within the first torsion bar bracket.

8. The nested torsion bar according to claim 7 , wherein the rubber bushing is adjacent to the proximal end of the second rate torsion bar.

9. The nested torsion bar according to claim 5 , wherein the second rate torsion bar is hollow and receives the first rate torsion bar therein.