I'm mechanically challenged. While washing the Wing I noticed the bolt in question was loose. I didn't have a wrench that size so tried to turn it with a pair of pliars but it didn't seem to want to tighten up. While riding, I could hear a vibration - the bolt had backed off. That bolt seems to be holding down a bracket but I haven't a clue what it's for. I bought an 8mm wrench to tighter it up but I can't get it tight. Did I stop turning it too soon or is there another reason it doen't tighten down? Actually, is it supposed to be tight?