General info:
What is the torque value required for the nut?
Typical torque values for the base nuts on a TPMS valve stem range from as low as 35 in.-lbs. of torque to as much as 80 in.-lbs. of torque. That’s quite a range. This doesn’t mean that any torque value within this range is acceptable. It means that the torque specifications for the base nut on one vehicle might re*@#$quire 44 in.-lbs., another might re*@#$quire exactly 62 in.-lbs., yet another might specify exactly 71 in.-lbs., and so on. Don’t guess. Look up the torque specifications for the vehicle you’re servicing to make sure you use the correct torque.
Why should the nut be replaced every time a sensor is serviced?
The nut is made of a softer metal than the stem, so it will be damaged – not the sensor – if it’s overtightened. The material of choice is typically aluminum. If the nut is over-tightened, it will develop hairline cracks.