I went through this with my old motor cop partner. He was pushing 80 and very unstable on two wheels.
He actually listened and quit . . . until some of his riding buddies talked him into a trike. No stability issues, but he was still a threat with diminished cognitive skills.
I sweated that out for a couple years until he passed from lung cancer. Miss ya, Norm!
Now we got another retired LEO in our Blue Knights, younger than I whose riding is really shaley and sux!
Folks complain to me how dangerous he is to ride either in front of or in back of. i have spoken nicely with him, but he is totally unaware of, and denies there is anything wrong with his riding. He is a real nice guy and a great member to our club. Why must I be the "bad guy"???
