Report "I bought a use Precor EFX 556. It's beautiful and appears barely used. It had some squeaking and the tech came and replaced the belt and that is gone. However, there is a clunking sound that comes from the right wheel as I reach the top of my stride. Other people get the same noise as well. I tried pulling it as someone used it to see if it could be influenced by weight. It rocks side-to-side slightly due to the compression of the carpet. I have tried my best to eliminate the weight distribution from the equation, but I'm still looking for answers. I may have to return it when it is otherwise a great machine. Anyone got an answer? Thanks"