Not gravel. Very rocky in long steep sections as of mid-May 2021, and since it's unmaintained it will only get worse. Challenging ascent and brutal descent on a drop-bar full suspension gravel bike with 40mm tires. ( Niner MCR ). Almost certainly better on a suspension MTB or fat bike, cuz unlike Pacheco Canyon Rd, there's no paved and/or smooth option for the descent. Also, if there's still man-made snow on the ski runs, you might not make it to the peak. But the views from the upper traverse are awesome anyway.