Yet another speed wobble query

Speed wobble is resonance - a particular bike and rider has a particular resonant frequency. Almost any change in the resonating mass or damping can cause or cure speed flutter. Knee to the top tube adds damping, so it's a good way to kill it when it happens. In theory going faster can also cure it, and then it'll come back as you slow down (unless you're braking hard, obviously). In practice it's a brave rider who speeds up!

You can never be sure it isn't a possibility until you've ridden a fair bit at whatever speed you're worried about, and then don't change your setup. Even then minor variables like tyre wear mean you can't be quite certain it won't happen.

The most important thing is not to panic if it does happen. Despite feeling unstable, the bike will keep going just fine. Don't panic, ride the bike lightly and let it move under you.

I've found a very effective measure to prevent speed wobble is not going very fast.

Another measure, if you have a big enough load is a trailer like the Yak Bob- hardly any effect on handling while moving.

I had a touring load on once that caused a nearly constant speed wobble. I nearly went straight back home. After a few minutes of practice, I found that I could stay light on the bars and stop it from happening. It was a little stressful, though. Luckily it was only an overnight trip, 40 miles each way.

It would be a bit harder to ride with my knees clamped on the top tube, though.