“All fire road, but great views and almost impossible to avoid when riding the north side of Mt. Tam.
— Jackson Ratcliffe
Eldridge Grade is one of the key access trails to the top of Mt. Tam from the North. Unfortunately, it is basically all fire road, so from a pure riding perspective, it's not the greatest trail in World. But what it lacks in flow, it more than makes up for with scenery as it does give you access to some of the best views in Marin.
Starting from the bottom, Eldridge starts off with a nice section that, although an old road, has narrowed and can almost be classified as singletrack. The middle section is gentle fire road with a few slightly steep sections, but nothing vicious. The top section has some spectacular views but is very rocky and not an easy ride going up, but ok going down.
Unfortunately, the Marin Municipal Water District (MMWD) has a strict no bike policy on anything other than fire roads. So as you ride Eldridge Grade, you'll see many beautiful trails that you are not allowed to ride. So enjoy the views, get some exercise, and hope that the MMWD will someday see the light and let bikes on some of the singletrack trails.