I've jacked up the balljoint placing the jack a couple inches left of right of the center of the rotor. Next roll the rotor so it slowly pushes up on the ball joint. By having the jack so far out on the hub it will help keep the axle from popping out. For some reason this works better than slowly jacking from the middle of the rotor. Trust me, i've done 3 tours and this little trick makes things much easier.
