My bike (trek remedy 66) has a problem with the bolt that holds the rear swing arm to the frame. It seems ever moderatly long ride it comes loose and i have to tighten it all the time. some times it gets so loose i can feel the whole rear end swinging left and right. it never used to have this problem. i have now had it for 1 year. it it because there is dirt in it so it cant be fully tightend?