Originally Posted by
Justin Zazzi
I didn't see clues for a specific material or product. The link you have for absorbing materials is a great start. If you want to try it, aim for one that is hydrophobic (won't absorb water) and then you'll need a plan to shape it and make it hold the shape. That article mentions significant fabrication and custom work to turn the material into custom shapes and so on.
The article also mentions if the tire noise is masked by wind or engine noise then the sound treatments don't do much. Are your tires really super noisy?
Kinda related: from day one I had tons of road noise coming into my car from the floor and I assume the wheel wells so I removed the seats and carpet and made a bathtub shape out of MLV to act as a sound barrier. It was a ton of work but it works great and I don't have to worry about the weather-proof reliability of putting something in the wheel wells.