Well today my baby developed an annoying rattle in the rear tire are. ir sounds as if something is loose. All the lugs are tight, there no foreign oblect in the rim anywhere. It increases with speed, but up around 40 it quiets down. Sounds like a metal piece jiggling around. I took the center cap (center of lugs) off and noticed that the little cover that goes over the nut that secures the rotar and drums was loose. The cotter pin which is on the outside of this cover and interlocks with it was also loose. I tightened the cotter pin back down. But low and behild it started again after about 2 miles. The pin was loose again. Is there something that needs to be replaced, or do I just need another cotter pin to lock that cover down?