Those of us running bigger tires know how tight of a squeeze it can be back there. Lately, I've been hearing a pop/clunk/rattle in the back that was getting annoying. While trying to find the noise, I hit my spare and was able to reproduce it. Crawling under, I saw where the tire was hitting the heatsheild whenever I stopped or accelerated. It was made worse by the fact the the shield was loose and then rattling against the body. Here's how I fixed it.
TOOLS:
Brake quiet
BFH
Scrivet puller/needlenose
POM riveter (Harbor freight)
6.3x25.2 POM rivet (Harbor freight)
Step 1: Lower spare.
Step 2: Hammer any spots where witness marks from tires appear
Step 3: Remove plastic rivet
Step 4: Liberally apply brake quiet between heatshield and body
Step 5: Resecure shield with POM rivet. (This holds much tighter than the original)
Step 6: Re-install spare
Before: (You can see a small black mark from the tire to the right of the rivet)
After: (The whole backside is covered in brake quiet)