Originally Posted by
tomato coupe
How did you not see someone sitting on your wheel if you glanced over your shoulder?
Not all of us have your rubber neck. Also sometimes drafters drift to one side or the other.
The rider drafting unannounced was asking for anything an unsuspecting rider might do. This wasn't on you, OP. If he wanted otherwise, all he had to do was speak up. (That's curtesy also. Drafting puts the rider ahead at additional risk. Granted not a lot, but it's there. He/she should be informed.)