Bad Bass

Bad Bass, run at Lake Chabot Regional Park near Castro Valley, is a beloved Bay Area trail half-marathon that draws a loyal crowd of around 269 finishers each year. First run in 2016, the race has grown steadily, with about 22% of runners returning year after year. The course, a true ‘ultra half,’ clocks in closer to 13.7 miles with roughly 1,500 feet of elevation gain, winding across fire roads and shaded single-track under eucalyptus and oak. Reviewers rave about the stunning lake views and the ‘steep hills’ that give the course its challenge, but the production value—scoring a perfect 5.00 for organization—keeps the day smooth and welcoming.

The atmosphere is pure community-driven: a small, local field from about four states, a whimsical fish-in-a-kilt race theme, and a spacious start/finish area where runners linger to swap stories. With typical race-day temperatures in the upper 50s to low 70s and little chance of rain, conditions are near-ideal for tackling this hilly, scenic loop. Whether you’re a trail newbie or a seasoned ultra runner, Bad Bass delivers a memorable morning on the trails.