Originally Posted by
McBTC
If you're not imagining things -- as everyone seems to suggest -- I'd have to guess the frame design is *****ed and is amplifying a wobbling under certain circumstances that others have not precisely duplicated. It doesn't always take a lot of weight (just where a lot of the weight is at --e.g., over the rear wheel) but it would require a flexible triangle (e.g, a bigger frame can sometimes be more flexible).
I doubt he is imagining it. The problem is that weight distribution is easily changed on a TT/tri bike just by things such as stem length and the aero extensions you choose. These are exactly the things that can contribute to speed wobble. And the overall weight distribution is far forward compared to a road bike.
Have you ruled out mechanical issues? headset and alignment?
Does it wobble regardless of how much weight is on the front end?
What if you plant yourself more solidly in the seat or pedals rather than the forearm pads?
What if you're riding the base bars?
Are you putting your knee on the top tube to dampen the vibrations?
Have you tried playing with any of the stem/bars to fix it? This may mean being a bit from your ideal fit.