Having troubles with my BB7 avid brakes. This time the outer knob fell off after I adjusted it a few days before. I did not notice it was gone till I had to make an adjustment on the road.

By the time I got home I had no braking power left. Turns out the pads were wore down almost too far. So after I got it all changed and back together the knob is still loose. It clicks on and stays on, but there is no friction holding the setting in place.

Is there a part missing? I looked all over where I found the red knob and saw nothing. (see the space between the knob and the body)

The knob does turn the pad adjustment.