After installing the Smittybilt SCR Classic Rear Bumper with Spare Tire Carrier, I conducted a trail test and heard some metal-on-metal rattle (my 33X12.5" spare weighs 82 pounds). I discovered it was coming from the latch assembly where the bolt engages the strike plate (square hole into which the bolt engages). The quick ten cent fix was to insert a rectangular piece of rubber (you can cut a tire tube into a 1" X 4" rectangle) and insert it into the hole, then close the spare tire carrier and engage the bolt into the rubber insert. The bolt is now nested in rubber which provides a cushion between the bolt and strike plate. The rattle is now gone.
Here's a link to a video of a post-fix ride.
Jeep YJ Mud Bath - YouTube