From what I recall, the road is pretty dreary until you get to Needles, then starts climbing on the other side. There's a bit of the old route 66, then you climb some more to Flagstaff. It's even higher to get to the South Rim so you would want some warmer gear handy.
You see some neat stuff coming in from the South Entrance, but you would need to park your bike and ride the shuttles to get the true measure of the canyon. If you've never seen it, you owe it to yourself to do it up right and see all you can.