Methods and apparatus for suspending vehicles

1. A shock absorber for a vehicle comprising:

a gas spring having first and second gas chambers, wherein the first gas chamber is utilized during a first travel portion of a piston and the first and second gas chambers are both utilized during a second travel portion of the piston;

a bulkhead separating the first and second gas chamber, the bulkhead having a valve with a valve shaft biased into sealing engagement with a valve seat in the bulkhead, the valve shaft at least partially extending into the first gas chamber, wherein the piston is constructed and arranged to contact the valve shaft at a predetermined position of the first travel portion, thereby opening the valve and utilizing both the first and second gas chamber; and

a travel adjustment assembly configured to selectively communicate the first gas chamber with a negative gas chamber, the travel adjustment assembly including an inner tube at least partially disposed within an outer tube, the piston movable relative to the outer tube and the inner tube movable relative to the outer tube, the inner and outer tubes each having at least one aperture in a wall thereof forming a communication path between the first gas chamber and the negative gas chamber at predetermined positions of the piston in a compression stroke of shock absorber.

2. The shock absorber of claim 1 , wherein the shock absorber is disposed in a leg of a fork.

3. The shock absorber of claim 2 , wherein a second leg of the fork comprises a fluid damper.

4. The shock absorber of claim 1 , wherein utilization of the second gas chamber is brought about by a predetermined pressure developed in the first gas chamber.

5. The shock absorber of claim 1 wherein, at an end of the first travel portion, gas pressure is substantially the same in the first and second gas chambers.

6. The shock absorber of claim 1 wherein, at a beginning of the first travel portion, gas pressure is substantially the same in the first and second gas chambers.

7. The shock absorber of claim 1 , wherein the valve shaft extends non-coaxially into the first gas chamber.

8. The shock absorber of claim 7 , wherein an initial position of the valve shaft relative to the piston is user adjustable.

9. The shock absorber of claim 1 , wherein the piston is constructed and arranged to contact the valve shaft in the compression stroke of the shock absorber.

10. The shock absorber of claim 1 , wherein a length of the first travel portion is adjustable.

11. The shock absorber of claim 10 , wherein the length of the first travel portion is adjusted by changing a length of the valve shaft.

12. The shock absorber of claim 1 , wherein, the first gas chamber is located on a first side of the piston and the negative gas chamber is located on a second side of the piston.

13. The shock absorber of claim 1 , wherein, in the compression stroke of the shock absorber, the first and second gas chambers are located above the piston and the negative gas chamber is below the piston.

14. The shock absorber of claim 1 , wherein the outer tube and the inner tube are concentric tubular members.

15. The shock absorber of claim 1 , wherein the piston is constructed and arranged to move the valve shaft into the second gas chamber.

16. The shock absorber of claim 1 , wherein a longitudinal axis of the valve shaft is parallel relative to the inner and outer tubes.

17. The shock absorber of claim 1 , further including a seal ring for sealing an annulus between the inner and outer tube.

18. The shock absorber of claim 17 , wherein communication between the first gas chamber and the negative gas chamber is blocked by the seal ring when the piston reaches a predetermined position on the outer tube.