A Roewe 550 car with a mileage of about 28 thousand km. The car owner said that the left rear wheel of the car would make a different noise from the left rear wheel, which is like the friction between the tire and the chassis. After receiving the car: first test the car to verify the fault phenomenon, the fault is true, the left rear wheel will issue "Chi Chi Chi" sound. After the release of the car brake, the lift is raised with the lift and the left rear wheel is rotated to find that the tire appears to have a hairpin during the operation of the tire (the rotation will stop at a certain point); the right rear wheel is rotated and the right rear wheel runs smoothly. The left rear wheel is removed and the brake disc is rotated. It is found that the brake disc has a partial deep friction with the brake disc during the rotation process. Remove the left rear brake caliper and brake friction disc to clean the dust on the bearing surface, measure the warpage of the bearing surface and find that the bearing surface is warped seriously. After changing the new bearing, it is measured again and the deflection is restored to normal. It is proved that the axle head has no deformation. After the brake disc is cleaned and installed, the deflection of the brake disc is measured in the normal range. The reason for this fault is the plane deformation of the bearing, which leads to the interference between the brake disc and the brake disc in the state of the car without braking. Elimination method: replace the left rear wheel bearing.