About 3 years back I bought a set of Kuryakyn Iso Floorboard Covers. After installing them I noticed "more" floorboard vibration.
I was somewhat disappointed to say the least...and decided to experiment a little with some clear silicone rubber caulking and flat washers.
Here is what I did:
1. I created a series of 1/4" diameter round beads of silicone caulking about 1 1/2" apart on the under side of the Kuryakyn floorboard covers.
2. I filled the deep sockets under the stock floorboards with silicone caulking and carefully placed flat washers flush onto the wet silicone "careful" not to allow the washers to touch the floorboard metal...choose washers that give you 1/16" + clearance all around. Let the silicone cure on both the covers and stock boards for 1 or 2 days.
3. Once cured...drill through the cured silicone filled sockets from the top side of the stock boards to ensure the drilling is centered...
4. Place the Kuryakyn Covers over the boards and carefully screw them down from underneath just enough to compress the silicone beads a little.
*MAKE SURE THERE IS NO METAL TO METAL CONTACT BETWEEN BOARDS AND COVERS*
*BE SURE TO USE BLUE THREAD LOCK TO PREVENT SCREWS FROM COMING LOOSE*
Happy Riding with less Floorboard Vibes!!