it happened once to me.... just after i had recovered from a clavicle fracture, scared me to hell.
bike has always been the same on 100's of rides down that hill. That day (i think) was high bottom2top cross wind and i was holding the bar too tight and my butt was planted too hard on the seat.
here is what i have told myself in case i need it...
- (made practice) pedal even if at low cadence, except on/close turns
- (made practice) knee or thigh in a position to dampen along the top tube
- butt raise/shift slightly back to change pivot point -- i know this can be scary, but, fingers crossed i dont have to do it
- dont over grip the handle bar --- now, this is where i think i made it worse on that ride, i gripped it harder... thinking it was the front wheel.
luckily on that ride, i was able to slow down.. first shaking bike,.. then shaky rider!