One problem related to brake disc has been reported for the 1999 Jeep Wrangler. The most recently reported issues are listed below.
Warped rotors caused braking and steering difficulties. One rotor needs replacement and the other one needs to be turned. This problem is listed on the technical service bulletin as disc brake rotor pulsation. The steering wheel would shake so badly during braking it was difficult to steer. Dealer states rotors wore out due to wear and tear, but the brakes pads have very little wear on them and do not require replacement. Warrenty on brakes was only good to 12k.