Sorry - I can't think of any near BART. There's no BART line to Marin, where I live, regrettably (it would make for such a better commute - and that's where all my bike stores are). Anything in Berkeley near one? I can't think of anything in the city nearby. Best bike shop I know of in the city is City Cycle way down in the Marina. Also Sports Basement, in general, rocks. But they're not near BART either.