Mt Umunhum Rd starts at the top of Hicks Rd. Unfortunately you cannot go all the way to the top of Mt Umunhum due to a privately owned section of the road.
But the climb is still great: there are a number of section with a grade around 15% and you can enjoy great views over the South Bay, to the mountains South and across to Mt Hamilton.
After 2/3 thirds you get to a gate, you can easily pass it on the left side. The end of public road is clearly marked with road signs and big white strip across the pavement saying "No Bikes!" in red paint.
Mt Umunhum with the abandoned Air Force station
Loma Prieta to the South
View East from the turnaround point - Mt Hamilton in the background
The peak of Mt Hamilton above the clouds (or smog)
The last steep section - looking South-East
A few meters lower - looking East
Views over the San Jose and the South Bay
Two more of the steeper sections