There are no TPMS on volvos since 2016, they using rotation speed to determine under inflation

 

So it is a "type" of TPMS. Is the sensor external to the wheel then? In such a way, I mean, as to have no impact on changing a wheel out, for example.

 

Yes.

This is a new type of TPMS system which relies on monitoring the rolling diameter to determine adequate inflation.

it's called "Indirect TPMS". You can read about it here.

It has both advantages and disadvantages compared to direct TPMS.

Drawbacks:
Unlike direct TPMS it cannot give you the tire pressure in measured units.
System needs to be "calibrated" when wheels are changed. You fill the tires to the proper spec, press the calibration button in the vehicle screen, and it uses the next several miles of driving to calibrate the rolling diameter.

Benefits:
Less unsprung weight in the wheels.
Easier to balance wheels with new tires
Less cost.
Never have to worry about TPMS communication issues again.

Some like one, others like the other. I am mostly indifferent these days.

 

I have had issues with the indirect TPMS on my 2017 V60. When heading out on a long interstate road trip, the tires will naturally heat up and the pressure will go up by several psi (natural gas law and all that). Because the car does not carry the same weight front and rear and because power is going to the fronts only, the fronts will heat and expand more than the rears, causing a difference in tire rpm front-to-rear. So, 200 miles into the trip -BING!- the light comes on.

The choice is to either equalize tire pressures or re-calibrate the system to the new pressures.

By the way, I ran across a page in my 2020 V90 owner's manual that specifically states that you should reset the system whenever you change tire pressures, and that would certainly apply when you change tires. It's a menu choice in the My Car folder, I believe. Check your manual.

 

you should probably take your car to a dealer to get the indirect TPMS checked out or something else - either your driveline or even alignment. Both direct and indirect TPMS only throw an alarm when the perceived pressure difference exceeds a certain threshold (for indirect this is proxied by rotational speed differences) - typically a real or indirect pressure difference in the 20% - 25% range. If your car front/rear Tire temp differences are wide enough to throw an alarm, either there is something wrong with the system, or something wrong that is causing your fronts to heat up so dramatically different than your rears to throw an alarm.

 

And this is why I check this forum daily. You all are a wealth of information and I thank you heartily.

Tack.

 

And this is why I check this forum daily. You all are a wealth of information and I thank you heartily.

Tack.

Same here. Wow. I assumed it had normal sensors and wondered why the screen just had green and didn't tell me the exact PSI like my 10 year old Honda. Now I know why.

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Yes, you should always recalibrate when you replace your tires. Also, it helps to check all tire pressures when you have to inflate one tire so that you can more accurately ensure the differences actually exist between tires.
I have an issue where the same wheel always seems to lose air, even after mounting new tires to that wheel (not a puncture issue). When I check the pressure, it is indeed lower in pressure than the other tires.