I've carried a few times (legally), but basically I've given up. It's been proven many times, you can't shoot and ride a bike (or drive a car) at the same time. Best to be aware then get the heck out of the situation on your two wheels. If chased by a car, hang a u-turn and ride the wrong way down the road for a while as an emergency measure only. No car would dare do that.

Plus, I ride my bike to work. No firearms allowed at work.