/ Speed wobble....
Take a look at that. Same thing happened to me a few months ago and I asked on here.
It has started to happen a couple of times since at about 45 mph ish, but I have managed to stop it by sticking a knee on the cross bar to change the resonant frequency.
To stop it happening the advice on that thread was basically.
Reach for breaks in an even way - ie not place all the weight on one side while reaching for the break with the other side.
Stick a knee on the cross bar or grab the bar with both knees.
Lower your centre of mass by standing out the pedals rather than sitting on the seat.
may not be the same thing that the OP is referring to. speed or 'death' wobble is very scary if you are not aware that it exists. The thing is that the tighter you grip the handlebars and try to stop it, the worse it can become. Solution is to get out of the saddle and/or squeeze the top tube with your knees/inner thighs. Its happened to me when I was shivering and in a cross wind. something to do with harmonics..?
As far as I know it only happens at pretty high speeds
Sometimes racers may get it because they would loosen the cones on the hubs for less friction but would cause the speed wobble. You said your bike has been recently serviced, unless you asked for the cones to be loosened the mechanics shouldnt. I've never had it happen to me just explained to me by a mechanic.
I am certain though honking cars are a main source....even at slower speeds.
A customer did complain to me that his bike was the reason (bull) and that if he was to swap it for a more expensive at a discounted rate that would stop the wobble (also bull) never the less the manager caved. he got his bike and he never complained of it again.
Loose cones feel horrible and I've never heard of anybody loosening them on purpose - they usually loosen themselves over time, after which they should be tightened.
Speed wobble is almost always a result of overly tense bike handling. It's natural to tighten up when you're going fast due to the fear. The trick is to stay loose, keep your weight back, and if you do start to wobble, lightly pull the back brake to anchor the bike and slow down. Thor Hushovd clocked 119km/h on one descent in the 2011 Tour, and I didn't see him wobble once!
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