Tpms

[uro1]

A few month ago I "found" a screw with my tire. The TMPS came on and the difference was 0,5bar. I had just changed to summer tires the week before so at first I just corrected the pressure in all tires and went on. The next week the TMPS triggered again and the difference was the same 0,5bar. So I guess that´s the trigger difference for the system.

[gaby]

Originally Posted by nu11eaf

If the pressures rise above or below the calibrated setting yes.

Since I change pressure regularly by 0.3 bar without clibrating, I assume this should raise the alarm.
But it doesn't. Perhaps it doesn't work.
I wonder how iTPMS detects other pressures if all 4 have the same. There are no sensors.
It also implies temperature compensation (as does the "true" dTPMS system of my motorcycle).

[nu11eaf]

Originally Posted by gaby

Since I change pressure regularly by 0.3 bar without clibrating, I assume this should raise the alarm.
But it doesn't. Perhaps it doesn't work.
I wonder how iTPMS detects other pressures if all 4 have the same. There are no sensors.
It also implies temperature compensation (as does the "true" dTPMS system of my motorcycle).

It has to have some leeway up and down to stop natural/normal pressure differences due to tyres warming up and cooling down. But I would think 4.3psi would activate a warning but it may require a little more. 5psi might be the trigger point, I really don't know.

[gaby]

Originally Posted by uro1

A few month ago I "found" a screw with my tire. The TMPS came on and the difference was 0,5bar. I had just changed to summer tires the week before so at first I just corrected the pressure in all tires and went on. The next week the TMPS triggered again and the difference was the same 0,5bar. So I guess that´s the trigger difference for the system.

You didn't mention the MY of your car.

[cassell]

It's definitely heat related, on a very hot Saturday in June (yes we did have one!) I went to a local vintage truck show and my car was parked on grass for several hours. When I came to leave the TPMS warning illuminated and all four tyres showed amber.

I drove home, the car cooled down, and the next day the message was gone.

[Fursty Ferret]

Originally Posted by gaby

I wonder how iTPMS detects other pressures if all 4 have the same. There are no sensors.

If you do a spectrum analysis of all four wheel sensor frequencies then simultaneous under inflation can be spotted fairly easily.

[gaby]

The alarm went of in case of higher pressure(s) also.
The fact remains that the TPMS in our XC90 doesn't raise an alarm after swapping
wheels/tyres and/or pressures by 0.3 bar/4.35 psi.
I wish the car had dTPMS, perhaps offered as an option/accessory.I find iTPMS a serious downgrade.

[Clan]

Originally Posted by gaby

The alarm went of in case of higher pressure(s) also.
The fact remains that the TPMS in our XC90 doesn't raise an alarm after swapping
wheels/tyres and/or pressures by 0.3 bar/4.35 psi.
I wish the car had dTPMS, perhaps offered as an option/accessory.I find iTPMS a serious downgrade.

Its cost ,It is very simple and it saves you and the manufacturer money . It costs the factory nothing at all as the components used have been on every volvo for the last 30 years or so and uses the screen which is there anyway, ..

[uro1]

Originally Posted by gaby

The alarm went of in case of higher pressure(s) also.
The fact remains that the TPMS in our XC90 doesn't raise an alarm after swapping
wheels/tyres and/or pressures by 0.3 bar/4.35 psi.
I wish the car had dTPMS, perhaps offered as an option/accessory.I find iTPMS a serious downgrade.

It will raise alarm if it changes 0,5bar.

[gaby]

Originally Posted by uro1

It will raise alarm if it changes 0,5bar.

Possibly, but by then you may have a problem.
What I expect from a decent TPMS system is to inform me before a problem is actually there,
giving me more time to anticipate and prevent from having to stop the car at that moment.