The difference between a mountain bike helmet and a road bike helmet is not just the visor. A mountain bike helmet is a completely different helmet than a road bike helmet. And vice versa. A mountain bike helmet features a beefy, protective design that stays securely on your head through all the ups and downs and in-the-air moments on your ride. A road bike helmet features a lightweight, aerodynamic design to reduce drag.
Each is built to support that rider’s specific needs. For example, a mountain bike helmet’s visor is not only designed to shade your eyes, but it also acts as a shield for your face so you can duck into turns through brush and branches. Does a road bike helmet need a visor? No. You just wear sunglasses.
So, can you use a mountain bike helmet for road biking? Sure. But if you’ve got a good road bike helmet that’s built to be light and aerodynamic for longer rides that is the smarter choice.