Thanks for the photos and the article. Brings back many memories of my youth while growing up in the Contra Costa County area. I enjoyed hiking up Mt Diablo and around its foothills several times in the ‘80s while in junior high school. In the ‘90s I made several rides on my motorcycle from Livermore on Mines Road out to Mount Hamilton and the observatory there close to where you hiked. Incredible scenery and fond memories.
Mines Road is incredible...all high plateau ranch land. When my son was learning how to drive, his first mountain driving experience with me was going up Mt. Hamilton Road to the observatory, then taking Mines Road over to Livermore. That must have been a real blast on your bike!
Another good ride is Corral Hollow Road from Tracey to Livermore (where it changes to Tesla Road).