Many ways to skin a cat, but here's how I do it.
Camera in AI Servo tracking (or your cameras eaquivalent), with shutter priority selected. For 3/4 on shots, I use a shutter speed between 1/200 and 1/320s. I then vary ISO to give me an aperature of around f8 to give sufficient DoF.
Select an AF point that allows you to track on a high contrast area of the bike / car and give you the composition you need. There is no need to slavishly rely on the centre AF point. Ideally you want to track the car / bike for at least a couple of seconds, and keep tracking for a second or two after you've taken the shot.
Many other ways to do it, as I'm sure others will chip in with.
Cheers,
Simon.