I would like to know when pulling a pistol in self defense is allowable? After the crash or before?
We had close calls in KY this weekend with cars squeezing in between the bikes trying to pass.
As a general rule any "deadly force" would have to be justified in a self defense situation. In that the perpetrator had the means and ability to cause serious bodily harm to you or others. And in some states the victim had no other recourse than to use deadly force to stop the aggression.
So you couldn't shoot someone for being stupid or careless.(If so the roads would be littered with them.) You would have to convince a judge or jury you had no choice to defend yourself and that the suspect couldn't be stopped any other way.
So to help answer your above question, before the crash if it can be proven that the driver saw you and deliberately was aiming for you or another with the intent to cause harm. A car is deadly force.....You still have to consider what would happen with that car if the driver was shot, would it run into other bikes or cars and hurt an innocent?
After a crash you probably wouldn't be justified in your use of deadly force unless the driver was aiming for someone else or returning to finish you off. A court would look at it as "does the suspect still pose an imminent danger to someone or is the threat over with?"