I like to keep up with my tire pressure. So I hit the "Vehicle" button frequently to bring up the display of normal and actual pressures.


I've noticed that the specified "Normal" pressures for my 20 inch tires changes a bit. Its not always the same number from day-to-day...close but not exactly the same.


Has anyone else noticed this?

 

Pressure is a function of ambient temperature. Therefore, your pressures will vary during different periods during the day and night. These pressures can vary as much as four pounds in a 20 inch tire.

 

I am familiar with the Gay-Lussac's law defining the temperature and pressure relationship.


But now I realize my post was not clear.


The display shows a "specified" pressure for 3 different driving speeds, including "normal", and the "current" pressure. As you pointed out the current pressure will increase as the tyres warm up. However I have noticed that the specified pressure also jumps around a bit. That's what I do not understand.


Is it possible that the car is so smart that the "specified" pressure climbs a bit after driving a while in recognition that the tyres have warmed up and the "current" pressure has increased?


Next time you take your car out open the Vehicle display and see what the initial specified pressure is for normal driving speeds and see if it changes over time a few degrees like mine does.

 

Sadly, I have disarmed my TPMS as I found it unreliable and prone to battery failure in the transmitters. Consequently, I won't be able to answer your question. It does seem plausible that the car is "smart" enough to adjust.

 

 

This topic is covered several times in this forum. Here is an example.