From TST's FAQ:
Do I need special valve stems?
No, you do not need special valve stems, but you do need commonly available metal valve stems.
The added weight of the sensor on a rubber valve stem could cause problems that will be avoided by using metal valve stems.
Most motorhomes and commercial transport vehicles come equipped with metal valve stems. If you do need metal valve stems, they are not expensive; a recent customer had 6 valve stems replaced on a 30’ gooseneck racing trailer for $36. They are available and can be quickly installed by any tire dealer.
Everyone should read their manual(s) before installing any safety item on their vehicles. Understanding how and why they work as they do will keep you safer in the long run.
That said, thanks for the heads up for those that still choose not to read the manuals and/or choose not to follow their recommendations....Dennis