From my previous post - #50, you will note that I purchased a TM510RV system. As it is not recommended to install the valve cap sensors on the rubber valve stems that come with the Sprinter, I went to a local tire shop for advise and a quote. Their advise: the current rubber valve stems are rated for maximum of 50 psi which is less that the recommended tire pressure. i.e. they should be changed out even if you are not installing a tire pressure monitoring system. Cost: they are charging $12 per wheel, which seems reasonable considering that they have to remove the wheel, break the tire away from the rim, install the new valve stem, reset the tire, balance the wheel and install back on the unit.