so most of the bikes i own have fenders, especially my cruisers. now i am ocd for those little noises that my bike makes that it don't need to make. one of my pet peeves, besides the word pet peeve, are road noises transfered thru the fenders sometimes or just general fender rattles.
i had a rattle from the rivit holding the mounting brackets to my rear fender of one of my cruisers and it bugged me. so i took a piece of scrap innertube rubber, cut it really small, folded it over once and slide it between the mount bracket arms and under the fender out of sight. i did this to the front as well and then to my other cruiser with demountable brackets, made a rubber template between the bracket and where it bolted to the under side of the fenders. a bit time comsuming with the cutting and sizing, and putting the fenders back together, but for both bikes, it made a big difference. both bikes had noroad noise transfered from the wheels and into the fenders and were noticably quieter while feeling more solid at the same idea. and since everything fitted out of view under the fenders and between the brackets, you can't even tell i did anything at all.
just one of those little ideas i'd share with you cuz it killed the road noise transfer coming thru the fenders and eliminated any metal to metal rattles and contact. and i know there are rattling fenders out there.