Bad tie-rod ends result in feathered patterns developing in the tires as they wear. With the vehicle suspended on a rack, a service technician is able to move the wheels back and forth when the joints are bad.
Manufacturers install tie rods in pairs, with an inner and outer tie rod for each of the front wheels of the vehicle. They have a threaded end with a nut that allows for adjustment. This adjustment is the toe-in and toe-out used for a front-end alignment.
Tie rods connect the steering wheel to the front tires of the vehicle. They are ball joints that allow the tires to remain on the road despite irregularities in the surface. Worn tie rods require immediate replacement. If the tie rods fail, the driver is no longer in control of the vehicle.
A rubber boot protects the ball joint from moisture and grit while holding the grease for lubrication in place. These boots crack and wear over time. A damaged boot leads to failure of the joint.
During regular maintenance of the vehicle, technicians should check the tie rods. If the joints allow the addition of lubricant, it is important they avoid adding more grease than necessary to prevent damage to the joint.