If you suffer a violent shimmy on a descent with your hands on the
bars, how could the back wheel not be involved? I have had shimmys
where the rear wheel feels like it is skipping around, but was too
engaged in staying upright to take the time to look behind. I'm
convinced that the sort of shimmy you experienced is different from
that described in the faq. My own feeling is that these events are
closer to what people who study motorcycle dynamics call weave.

LGF