I'll add in that a friction drive is a great piece of kit for lightweight road bikes. And, no, they don't eat tires anymore, lol. I have the OneMotor, but there are others like the Add-E, E-go, and Rubbee or you can do it yourself with instructions from the great folks at Endless Sphere.
I love mine, it's adds less than 5 lbs to my bike, and flies up hills.