John_V 

I have tried both eyeglass and helmet mounted mirrors and both of them worked great. My preference was a helmet mounted mirror. As my mileage increased and I was doing longer and longer rides, I added clamp on aerobars on my road bike to help relieve some of the shoulder stiffness I was getting. As soon as I would get on the aerobars, those mirrors became useless. They're great if you always ride upright or in a fixed position as the adjustment doesn't vary much. Once I went aero, all I could see with my helmet mirror was tree tops and sky. To see what was behind me, I had to get back to the hoods.

At 73, my neck doesn't turn around like it used to so looking over my shoulder isn't an option. After trying several types of mirrors, the one I finally settled on was the CycleAware bar end mirror. It's adjusted so that I can easily see behind me while riding on the hoods or a quick look over my arm, while on the aerobars. However, for my last birthday, last October, the wife got me a Garmin Varia rear radar, just prior to my cross state ride. I now use it whenever I'm on any street and use my mirror primarily to see which lane a vehicle is in when on a multi-lane road. As nice as mirrors are, there's not a mirror on the market that notifies you of a vehicle(s) approaching 153 yards away. It's paired with my Wahoo Bolt and the LEDs on the computer help with visual notifications along with the audio notification you get when a vehicle is detected. My radar is like my American Express card; I don't leave home without it.