Wheelchair suspension

1. A wheelchair suspension comprising:

a frame;

a drive assembly pivotally mounted to the frame at a first pivot axis;

at least one caster pivot arm pivotally mounted to the frame and coupled to the drive assembly;

a variable length motion transfer member coupled to the drive assembly and the at least one caster pivot arm such that motion of the drive assembly is transferred to the at least one caster pivot arm by the variable length motion transfer member; a front caster coupled to the at least one caster pivot arm;

wherein torque applied by the drive assembly extends the variable length motion transfer member to a maximum length.

2. The wheelchair suspension of claim 1 wherein the at least one caster pivot arm is pivotally mounted to the frame at a second pivot axis and the first pivot axis is in front of the second pivot axis on the frame.

3. The wheelchair suspension of claim 1 wherein variable length motion transfer member is a shock absorber.

4. The wheelchair suspension of claim 1 wherein the variable length motion transfer member comprises a spring.

5. The wheelchair suspension of claim 1 wherein the drive assembly is mounted to a drive assembly pivot arm that is pivotally mounted to the frame at a first pivot axis and at least one caster pivot arm is pivotally mounted to the frame at a second pivot axis and the first pivot axis is in front of the second pivot axis on the frame.

6. The wheelchair suspension of claim 1 wherein the drive assembly pivot arm is pivotally connected to the frame at a first pivot axis and the at least one front caster pivot arm comprises first a first caster pivot arm pivotally coupled to the frame at a second pivot axis and second front caster pivot arm pivotally coupled to the frame at a third pivot axis.