Harry Houghton shows how to skin a spring in Maya so that it still looks like it is a rigid element.
Springs are tricky to rig. You need to set up compression and stretching so that it will act as a spring during animation. Sounds simple enough, but a simple deformer will also squash and stretch the spring itself, and not just the spaces between the coils. Lead Rigging TD at Axis Animation Harry Houghton put together a short video that shows us how to rig and skin a spring so that it looks correct.
The key is to create an intermediate skinning mesh for the spring. Houghton creates a thin version of the spring based off of the original geometry to work as the medium. A great way to learn how to rig a spring is to compare and contrast methods. One time Paul Atkinson did just that in a previous post he compared two techniques for rigging a spring system for accuracy in Maya – Check that out here.