I am running RFT's and I think we are talking about the same thing, below is right from the book. I have plastic caps with O rings and I have had a tire failure, the warning system functioned properly.

Flat Tire Monitor FTM (2006 ALL 3 Series OEM Tire Configuration)

The concept

The Flat Tire Monitor monitors tire pressures while the car is being driven. The system reports any significant loss of pressure in one tire in relation to another. If a tire loses pressure, its rolling radius changes, and this in turn alters the speed of rotation. This change is detected and is reported as a flat tire. Functional requirement in order to assure the reliable reporting of a flat tire, the system must be initialized for the correct tire inflation pressure. The system must be reinitialized each time a tire inflation pressure has been corrected or a wheel or tire has been changed.

System limitations

The Flat Tire Monitor is unable to warn the driver of sudden, severe tire damage caused by external factors, nor can it identify the gradual loss of pressure that will inevitably occur in all four tires over a lengthy period of time.

• Valve stem caps question on E92 wheels (pic) - mgruber 2008-03-21 01:59:17 (162 views)
  • Re: Valve stem caps question on E92 wheels - 74u2 2008-03-22 19:12:28 (96 views)
    • Re: Valve stem caps question on E92 wheels - mgruber 2008-03-22 19:24:23 (96 views)
      • Re: Valve stem caps question on E92 wheels - 74u2 2008-03-22 20:01:02 (98 views)