Although I like recumbents as much or more than others here, I think you're on the right track that the shim/adjustment is related to the back issues. I'm going to guess (strictly as a layman) that you should see a sports therapist. You rode without the shims for years with no issues. You may have a 'frozen' muscle, i.e. one may be atrophied because you've never used it before; but now you are and it's being grossly over-worked. You may need to get it analyzed and some PT prescribed. Seeing an ortho is a great FIRST step; but the ortho's problem is that when you're holding a hammer, all the problems you see will look like nails. A GOOD ortho will send you to PT before trying anything invasive; but if he doesn't suggest it first, make sure you ask. Massage, acupuncture, or exercises might all help in your case. A good phys therapist may be better than the ortho at determining what's going on.
Last edited by BlazingPedals; 12-07-12 at 01:02 PM.