Clunking sound while slowing down...

[lt1transam]

We just bought a 2001 Tahoe about a month ago. The other night I noticed a "new" sound while we were slowing down. It almost is like an unbalenced tire sound when barely applying the brakes. I'm not totally sure if the brakes are what's causing it, but that's really ony when we can hear it. The only thing I have altered is I put new wheels with 285/50-20 Yokohoma Geolanders. They seem to be a nice quiet tire compared to the Good year GT II's that were on there. Anyone have any idea as to what this sound maybe? Oh yeah the truck has 40,000 miles and appears to be in perfect condition.