09-17-2023, 07:39 PM
(This post was last modified: 09-17-2023, 07:51 PM by quattro4awd.)
I guess this goes back to the old saying "third time is the charm".
![[Image: AIL4fc8NxmRwLqCi3JdvGvUVa1TQwgr2tFr0xxak...authuser=0]](https://lh3.googleusercontent.com/pw/AIL4fc8NxmRwLqCi3JdvGvUVa1TQwgr2tFr0xxak9PRFZ7-RUw9HzsN_znuFfazFQDXZxVov1Ipyyp3TtNbnoaZ4-ry62MP0nKhSKc90D2fIg6Rlu-Wxo9EPy0YVq1Bqed-BJYMLdLikxIsRFyCwESGQJXsP=w706-h941-s-no?authuser=0)
had some time to think about the issues I was having and a realization hit me... the old rule of thumb = tire pressure can grow up to 7psi (48Kpa) between a "cold" and "hot" tire.
I was riding right on the edge of triggering a TPMS low pressure flag warning but not quite far enough.
What I figured out in order to trigger and reset a TPMS warning flag:
1). the flag trigger threshold (differential pressure between the "tyre pressure" setting line item stored in the ECU and the physical tire pressure being produced by the TPMS sensor)
= 10psi (69Kpa)
2). once a low pressure flag is triggered, in order to clear / reset and turn off the warning flag
= tire pressure reading from the TPMS sensor must be raised to equal or higher than the "tyre pressure" settings stored in the ECU.
as I am not exactly sure what all is affected by the "tyre pressure" line items setting (I.E.= is it strictly for the TPMS system? or do these values actually get utilized by the steering, suspension, ABS, etc. as well?) I didn't want to have a large gap discrepancy between the ECU preset value and the physical cold tire pressure that all the wheels are set to for this reason.
so I did a compromise and the current configuration has:
1). all 4 wheels will be set to a cold tire pressure of 38psi (262Kpa)
2). all 8 "tyre pressure" line items are set to 280Kpa (approx. 40psi), this will give me a TPMS low pressure warning flag at 30psi (207Kpa)
the reasoning behind all this:
after moving to the taller 50 series sidewall tires, having tire pressures set to a cold base temp of 38psi produced the best handling responsiveness in my opinion. when all 4 tires were set to a cold pressure of 34psi (234Kpa) the S60 felt loose and wallowy in its handling. also when a single wheel's tire pressure drops down to 28psi (193Kpa) the S60 will again exhibit a loose wallowy feel.
in order to get a TPMS warning flag to trigger at 34psi where I initially wanted it to trigger, I would have to set the "tyre pressure" line items between 300Kpa (43.5psi) to 310Kpa (45psi). a previous attempt to set the "tyre pressure" line items to 300Kpa several weeks ago resulted in a configuration error being displayed. and if there are other vehicle systems that actually pull and utilize the "tyre pressure" line item set point to adjust other system settings for handling... it is probably best to keep those line item settings as close to what the actual physical tire cold pressure is set to.
had some time to think about the issues I was having and a realization hit me... the old rule of thumb = tire pressure can grow up to 7psi (48Kpa) between a "cold" and "hot" tire.
I was riding right on the edge of triggering a TPMS low pressure flag warning but not quite far enough.
What I figured out in order to trigger and reset a TPMS warning flag:
1). the flag trigger threshold (differential pressure between the "tyre pressure" setting line item stored in the ECU and the physical tire pressure being produced by the TPMS sensor)
= 10psi (69Kpa)
2). once a low pressure flag is triggered, in order to clear / reset and turn off the warning flag
= tire pressure reading from the TPMS sensor must be raised to equal or higher than the "tyre pressure" settings stored in the ECU.
as I am not exactly sure what all is affected by the "tyre pressure" line items setting (I.E.= is it strictly for the TPMS system? or do these values actually get utilized by the steering, suspension, ABS, etc. as well?) I didn't want to have a large gap discrepancy between the ECU preset value and the physical cold tire pressure that all the wheels are set to for this reason.
so I did a compromise and the current configuration has:
1). all 4 wheels will be set to a cold tire pressure of 38psi (262Kpa)
2). all 8 "tyre pressure" line items are set to 280Kpa (approx. 40psi), this will give me a TPMS low pressure warning flag at 30psi (207Kpa)
the reasoning behind all this:
after moving to the taller 50 series sidewall tires, having tire pressures set to a cold base temp of 38psi produced the best handling responsiveness in my opinion. when all 4 tires were set to a cold pressure of 34psi (234Kpa) the S60 felt loose and wallowy in its handling. also when a single wheel's tire pressure drops down to 28psi (193Kpa) the S60 will again exhibit a loose wallowy feel.
in order to get a TPMS warning flag to trigger at 34psi where I initially wanted it to trigger, I would have to set the "tyre pressure" line items between 300Kpa (43.5psi) to 310Kpa (45psi). a previous attempt to set the "tyre pressure" line items to 300Kpa several weeks ago resulted in a configuration error being displayed. and if there are other vehicle systems that actually pull and utilize the "tyre pressure" line item set point to adjust other system settings for handling... it is probably best to keep those line item settings as close to what the actual physical tire cold pressure is set to.