You wouldn’t ride with a blindfold on. Nor would you ride with blinders to obscure your peripheral vision (like horses wear). Yet, many riders keep their right and left mirrors adjusted in a way that provides the narrowest view (including an excellent view of their elbows).
Next time you hop aboard your bike, and before you pull away, take a careful look into each mirror. What do you see? Is the view in the left mirror virtually the same as the view in the right mirror? How much of the scene behind you can you see in both mirrors? If the scene is largely duplicated by each, try angling both mirrors outward to expand the width of your overall view. The ideal adjustment allows you to see a vehicle directly behind in either mirror but with minimal overlap of that image. You should have a distinctly different view to the outside of the mirror now as well. The left mirror should reveal more of the space adjacent to your bike on the left (where cars pass), and the right mirror should expand the view of the space to the right of your bike (where merging vehicles appear from), significantly expanding your total rearward view.
While we’re talking mirrors, it’s a good time to consider what other drivers see. Car drivers have a rearview mirror mounted on the windshield that provides exactly what the name suggests: a rear view. Cars also have two side-view mirrors mounted to the outside of the vehicle on the right and left side. Unfortunately, despite the name, those mirrors are typically adjusted inward to take in the same rearward view as the inside mirror. That means that vehicles—including our motorcycles—are easily obscured from the driver’s view. Be aware as you ride alongside other vehicles; if you can’t see their reflection in the mirror, they can’t see you!