Because they don't fit tight enough to the a-arm or knuckle, when greased it comes out between the bushing and a-arm/knuckle and not the bushing and sleeve. This makes it seize on the sleeve and rotate in the a-arm or knuckle. What ever bushing you use will fit loose so be sure to glue them in...and LET THE GLUE DRY before pumping grease in..wait a day. There is a seal ring on the RzR bushings and a seal lip built into the end of the CFM bushings that holds grease in and helps keep water out. These also require some pressure to force grease past them...pressure that will push that grease around to the outside of the bushing if not glued & sealed solid. ALL mine required gluing. I have some videos on this in the how toos. Once done...with the RzR bushings, you will have no more problems.