OT (sort of) - coil-overs can rattle over bumps. I was surprised and disappointed when I discovered this the first time I drove my car after they were installed. Of course, mine are not the MM coil-overs, but if I know it would be like this, I would not have bought them. I'd research it a little to see if people who have MM coil-overs have a problem with them rattling when they go over bumps.