Quote:
Originally Posted by fe7565
Also, I believe that the TPM measures "relative" pressure and not primarily a pre-set pressure. That means that if your last pressure reset was at 33psi then it will look for a -4psi change (just an example number) and it will warn below 29 psi. But if you reset it last time when the tires had 35psi, then it will warn you below 31psi and not below 29psi.
That's why in moderate climates I need to add air when winter comes, and take out air when spring gets here. In your case in Canada: add air in early September and take air out in late June  |
Every time you perform a TPMS reset, the reference pressure for each tire is based on the pressure in each tire at the time of resetting. TPMS warning pressures are also redefined at this time. I believe it takes a while for the system to fully reset because it’s tracking the revs per mile as a backup to the TPMS pressure sensor. It takes a long time to reset if you’re driving 10-30 mph whereas the reset is completed fast when moving at 40-60 mph. If it was just pulling a reference pressure, the reset would be quick and its duration would be fixed, not influenced by how fast or slow you’re driving.