Just stopped at the dealer service center asked to fill tire to 42 front 40 rear they said no due to the TPMS light going off they said they would go 5 above spec based on the inside door. I'm pretty sure they are BSing but I wanted to confirm on Prius chat.
around once a month, they hold pretty well. i got a screw a few weeks ago and sensor came on. first time in 9 years.
The dealer's answer is ridiculous. The TPMS will trigger if a tire drops below the preset psi number. You can reset that number (see owner's manual for the procedure). But even if you don't, having a higher pressure in the tires doesn't do anything- you would simply have to have more loss of air in any tire before the alert would be triggered. For example, say the system is set to warn you when any tire goes below 28 psi. If you start at 33, it goes off when you lose 5 psi. If you have 40 psi, it won't warn you until you have lost 12 psi, which you ought to notice just by driving. I prefer to run 42/40 and have reset the TPMS accordingly.
Right, I wasn't clear in my previous post, but it is triggered if a tire drops 5 psi below the preset desired psi number in the system. It doesn't compensate without you putting in a higher number if you raise your pressures to 42/40 as a lot of us have done. OTOH, more sophisticated systems track the pressure in each tire, and in the case of Cadillac, warn you of over inflation as well as under, again based on where you have the pressures when you initialize the TPMS. Maybe the dealer person mentioned didn't understand that raising the pressure would not have the same effect as lowering the pressure by 5 psi, thereby triggering an alert.
