Snowmobile suspension

1. A suspension assembly for a tracked vehicle having a chassis and an endless drive track, the suspension assembly having a longitudinal direction and a lateral direction, the suspension assembly comprising:

a pair of rails adapted for engagement with the endless drive track, the rails extending in the longitudinal direction;

a first suspension arm having an upper end and a lower end, the upper end of the first suspension arm being adapted for pivotally connecting to the chassis about a first lateral axis, the lower end of the first suspension arm being pivotally connected to the rails about a second lateral axis, the first suspension arm extending forwardly and upwardly from the rails;

a second suspension arm disposed rearwardly of the first suspension arm, the second suspension arm having an upper end and a lower end, the upper end of the second suspension arm being adapted for pivotally connecting to the chassis about a third lateral axis;

a rocker arm having an upper end and a lower end, the lower end of the rocker arm being pivotally connected to the rails about a fourth lateral axis, the upper end of the rocker arm being pivotally connected to the lower end of the second suspension arm about a fifth lateral axis, the second suspension arm extending forwardly and upwardly from the rocker arm;

at least one shock absorber connected between the chassis and the rails for biasing the rails away from the chassis,

at least a portion the second suspension arm being pivotally connected to the rails about a longitudinally extending axis relative to the rails, the longitudinally extending axis being laterally centered between the rails; and

a ball joint pivotally connecting the lower end of the second suspension arm to the upper end of the rocker arm about the fifth lateral axis and the longitudinally extending axis.

2. The suspension assembly of claim 1 , wherein the second suspension arm is pivotable about the longitudinally extending axis by a roll angle, and the roll angle is between 0 and 10 degrees with respect to vertical.

3. The suspension assembly of claim 2 , wherein the roll angle is between 0 and 3 degrees with respect to vertical.

4. The suspension assembly of claim 1 , further comprising another ball joint pivotally connecting the lower end of first suspension arm to the rails about the second lateral axis and the longitudinally extending axis.

5. A tracked vehicle comprising:

a chassis including a tunnel;

an engine connected to the chassis;

an endless drive track disposed below the tunnel and operatively connected to the engine for propulsion of the tracked vehicle;

a suspension assembly supporting and tensioning the endless drive track, the suspension assembly having a longitudinal direction and a lateral direction, the suspension assembly including:

a pair of rails engaging the endless drive track, the rails extending in the longitudinal direction;

a suspension arm having an upper end and a lower end, the upper end of the suspension arm being pivotally connected to the chassis about a first lateral axis;

a rocker arm having an upper end and a lower end, the lower end of the rocker arm being pivotally connected to the rails about a second lateral axis, the upper end of the rocker arm being pivotally connected to the lower end of the suspension arm about a third lateral axis;

at least one shock absorber connected between the chassis and the rails for biasing the rails away from the chassis,

the chassis being pivotally connected to the rails via the suspension assembly about a longitudinally extending axis, the longitudinally extending axis being laterally centered between the rails; and

a ball joint pivotally connecting the lower end of the suspension to the upper end of the rocker arm about the third lateral axis and the longitudinally extending axis.

6. The tracked vehicle of claim 5 , wherein the lower end of the suspension arm is pivotable about the longitudinally extending axis by a roll angle, and the roll angle is between 0 and 10 degrees with respect to vertical.

7. The tracked vehicle of claim 6 , wherein the roll angle is between 0 and 3 degrees with respect to vertical.

8. The tracked vehicle of claim 5 , wherein the tracked vehicle is a snowmobile, the suspension assembly is a rear suspension assembly; and

further comprising at least one ski operatively connected to the chassis by a front suspension.

9. A snowmobile comprising:

a chassis including a tunnel, the tunnel having a longitudinal direction;

an engine connected to the chassis;

at least one ski connected to the chassis by a front suspension;

an endless drive track disposed below the tunnel and operatively connected to the engine for propulsion of the snowmobile; and

the rear suspension assembly of claim 1 supporting and tensioning the endless drive track.

10. A suspension assembly for a tracked vehicle having a chassis and an endless drive track, the suspension assembly having a longitudinal direction and a lateral direction, the suspension assembly comprising:

a pair of rails adapted for engagement with the endless drive track, the rails extending in the longitudinal direction;

a first suspension arm having an upper end and a lower end, the upper end of the first suspension arm being adapted for pivotally connecting to the chassis about a first lateral axis, the lower end of the first suspension arm being pivotally connected to the rails about a second lateral axis, the first suspension arm extending forwardly and upwardly from the rails;

a second suspension arm disposed rearwardly of the first suspension arm, the second suspension arm having an upper end and a lower end, the upper end of the second suspension arm being adapted for pivotally connecting to the chassis about a third lateral axis;

a rocker arm having an upper end and a lower end, the lower end of the rocker arm being pivotally connected to the rails about a fourth lateral axis, the upper end of the rocker arm being pivotally connected to the lower end of the second suspension arm about a fifth lateral axis, the second suspension arm extending forwardly and upwardly from the rocker arm;

at least one damper connected to at least one of the chassis and the rails;

at least one spring connected to at least one of the chassis, the rails, and the at least one damper,

at least a portion the second suspension arm being pivotally connected to the rails about a longitudinally extending axis relative to the rails, the longitudinally extending axis being laterally centered between the rails; and

a ball joint pivotally connecting the lower end of the second suspension arm to the upper end of the rocker arm about the fifth lateral axis and the longitudinally extending axis.

11. The suspension assembly of claim 10 , wherein the second suspension arm is pivotable about the longitudinally extending axis by a roll angle, and the roll angle is between 0 and 10 degrees with respect to vertical.

12. The suspension assembly of claim 11 , wherein the roll angle is between 0 and 3 degrees with respect to vertical.

13. The suspension assembly of claim 10 , further comprising another ball joint pivotally connecting the lower end of first suspension arm to the rails about the second lateral axis and the longitudinally extending axis.

14. A rear assembly for a suspension assembly for a tracked vehicle having a chassis and an endless drive track, the rear assembly comprising:

a pair of rails adapted for engagement with the endless drive track;

a suspension arm having an upper end and a lower end, the upper end being adapted for pivotally connecting to the chassis about a first lateral axis; and

a rocker arm pivotally connected to the pair of rails about a second lateral axis, the rocker arm being pivotally connected to the lower end of the suspension arm about a longitudinally extending axis,

the suspension arm having at least one first position relative to the rocker arm where the first lateral axis is parallel to the second lateral axis, and

the suspension arm having at least one second position relative to the rocker arm where the first lateral axis is angled relative to the second lateral axis.

15. The rear assembly of claim 14 , wherein the rocker arm has an upper end and a lower end, the lower end of the rocker arm being pivotally connected to the pair of rails about the second lateral axis, the upper end of the rocker arm being pivotally connected to the lower end of the suspension arm about the longitudinally extending axis.

16. The rear assembly of claim 15 , further comprising a ball joint pivotally connecting the lower end of the suspension arm to the upper end of the rocker arm.

17. The rear assembly of claim 16 , wherein the suspension arm is a rear suspension arm; and

the rear assembly further comprising a front suspension arm having an upper end and a lower end, the upper end of the front suspension arm being adapted for pivotally connecting to the chassis about a third lateral axis.

18. The rear assembly of claim 17 , wherein the ball joint is a first ball joint; and

the rear assembly further comprising a second ball joint connected to the lower end of the front suspension arm, the second ball joint being adapted for pivotally connecting the front suspension arm to the pair of rails of the suspension assembly.

19. The rear assembly of claim 18 , further comprising a shock absorber having an upper end connected to the rear suspension arm.

20. The rear assembly of claim 14 , further comprising at least one cross bar disposed between and connected to the pair of rails, the at least one cross bar fixedly connecting the pair of rails to each other.

21. The rear assembly of claim 14 , further comprising wheels rotationally connected to the pair of rails;

wherein the wheels are disposed between the pair of rails and rearward of the rocker arm.