I thought I was the only B.C. owner with this problem! My dog is obsessed with cars out of fear. However i have yet to find a method wich prevents it, she is now 14 months old! As for the best way to prevent chasing bikes and joggers, as soon as you see one coming call the dog to you if he is off the lead, (a retractable lead might be a good idea) get him to sit and hold a treat on his nose so that he is distracted. Praise him and give him the treat of he doesn't chase them. Alternatively hold his attention with a toy and lots of chatter to keep him focused on you. If he has already learn't to chase i would suggest a master plus remote spray collar. As soon as they start to chase, press the remote control and it emits a harmless spray which startles the dog. These are very expensive at around £160, but you can rent them from trainers or vets.