Lose the knobs (at least the back one) if you're going to use your MTB with a trainer. I recently bought a CycleOps Fluid3 trainer and put my MTB on it to see how it would go -- couldn't turn the TV up loud enough to mask the howl of the rear tire against the roller! Get a slick for the back tire and you'll be much happier with the setup. Changing tires is good practice anyway...