@jeffsu Alan Yates, the creator of the lighthouse tracking system: "About 50 micron, yes they are post-assembly calibrated. Dismantling invalidates the calibration, so you should not remove the front covers unless you really need to. There is a small chance you can get it back together close enough you won't notice for the HMD and controllers, but the base station is more sensitive. If you unscrew the motors from the frame or touch the lenses it will need cleaning and recalibration to track properly." Parent link: https://www.reddit.com/r/Vive/comments/4...
I may have exaggerated a little, but the multitude of Reddit tracking wobble threads and experience with my own Vive indicate the lighthouse system may be more fragile than it looks. The motors' own vibration produces tracking wobble, I wouldn't recommend touching the motors and possibly adding to it. In practice it's not very noticeable, but look at your screen vibrate when you put the headset down.
It might be important to note that removing the face plates or even touching the motors breaks the factory calibration and will produce tracking errors in the future. Currently there is no way for the consumer to re-calibrate the sensors.