I bike all over San Jose and the hazard on our trails are homeless and addicts living by the creeks next to the trails. I created a handle out of 550 lb. paracord that is attached to my 33oz stainless steel Oakley Water Tank that I keep in my bottle cage. Very effective weapon to swing at someone’s head. (If I ever do, I’m ditching the cord because it is “illegal” as a flail).
I have a 5lb Kryptonite lock in the back loop of my messenger back. At night, I carry a surefire tactical flashlight on my strap pad to wreck the night vision of an assailant, plus it has a crenelated “striking bezel” as an impact weapon.
In my front pocket, I have always have one of my three Kershaw knives with speed-safe as well. Luckily, I’ve had no problems even riding in the Tenderloin of San Francisco. I made a wrong turn once by a housing project up there and rode as fast as I could with my knife in my hand. As a general rule, I stay out of Oakland or places with a lot of Trayvons around.
I plan to move back to Arizona or go to Texas in the next couple years. Then I can just carry a handgun when I’m on my bike.
I also used to bike all over the South Bay, but I’m too old and slow to dodge the bums these days. Stationary bike in front of a TV is a lot safer. :)