Panning isn't something I've tried before so I experimented with a few different shutter speeds. It's not perfect but this at 1/60 sec seemed to work best.
Very nice first effort. Depending on the cars speed you can go slower or faster on the shutter speed. As the shutter speed drops so do the number of keepers I get. I usually shoot 4 or 5 frames as I pan. That usually insures 1 or 2 good frames.
It takes time to get to the point where you can capture what you see. I can do it on occasion, but not on a regular basis. With post process you can have any number of looks.
I really like your hill climb pictures, I'm more of a car guy than a bike guy Rob. Here's a bike for you.