I have been searching for an answer to a problem situation I have encountered a few times now. When descending, often I feel as if my rear-wheel begins to wobble and the stability of my new carbon frame and campy zonda wheels come into question. I have noted this on technically simple descents (straight downhill without a single curve or bump) and real mountain passes (now 'oh-****' as opposed to 'yippie' moments). As one travels downhill, the downward force of the bike increases and leaves one mathematically more stable, yet I feel as I am playing in the cycling equivalent of the Tacoma Narrows bridge. My question is simple, am I hallucinating or is my perception of a real phenomenon for which I should take some corrective action?