Hey Stephen, Yeah, there are places that can become rocky, but that is where front suspension comes in. I have hiked it myself and it is a great trail. The mountain bike, to me brings in interesting moments like when you come across a FS road and you would like to know where to go. More chance to explore if you are on limited time. But for the rocky portions, that is why some portons are closed off. Those parts are just too much. But here you can take FS roads and fire roads to get around.
Something I found interesting is if you want to explore the parkway and are staying at Talihina State Park, you can take the FS roads or trails to the Ridges and back to camp, if you are staying at the park. Explore on bike and save the gas.