I'm still a newbie at operating my SV200. When I'm running on hard snow (common in southern Minnesota), it seems the tracks vibrate or rattle. In deep (for us), soft snow it's pretty quiet. Is this normal, or do I need to: 1. Tighten the tracks more, or 2. Worry about the guides rubbing against the rubber tires? In general, it seems to happen when it's not pulling hard (including coasting down a slope).