F-150 does it with perfection using circumference alone. It does the exact thing you said cannot be done. I have verified it myself.

It also perfectly calculates distance to empty in miles/kilometers.

The F150 uses direct TPMS sensors. It doesn't need to measure wheel speed to determine pressure, because it has pressure sensors inside of the tires.

2021-2023: https://parts.ford.com/shop/en/us/electrical/other-electrica...

2015-2020: https://parts.ford.com/shop/en/us/electrical/other-electrica...

2013-2014: https://parts.ford.com/shop/en/us/electrical/other-electrica...

It's true that it won't know the exact pressures, but it certainly knows which tire is spinning faster than all the others (due to the lower pressure, it has shrunk) so it could definitely tell you to check that one.

In fact, your example looks more like one overinflated (or perhaps overheated) tire --- RR.

You seem to contradict yourself in this post. You say they can tell one is spinning faster than all the others, however this one could also easily be the one inflated to the correct pressure, while the other three are overinflated. If the Volvo tells you to correct it and it is wrong, it could keep telling you to overinflate tires indefinitely. This could be why they don’t, which was OP’s original point.

When you inflate them you press the “set” button so it knows what the base is. If one suddenly starts geting more angular velocity constantly than it’s likely it lost air

Yes, if one decreases relative to the other, it’s easy to figure out that one changed.

You still don’t know for sure that it needs inflated, because:

1. setting tire pressures incorrectly is not uncommon

2. That button is user accessible and might be pressed inadvertently or by someone who didn’t set the tires correctly

3. If all tires change in pressure at the same time, it would be undetectable

This is why these systems generally tell you to “check” your tires, rather than inflate a specific one. If they made that assumption, your car could be telling you to inflate an already overinflated tire.

1. Just check the tires. 2. Read the manual 3. Not sure about every implementation but it still possible to tell by storing wheel rpm associated with engine rpm, gear and steering angle the first few miles after setting it.

There are many cars with tpms in the wheel that still won’t tell you what wheel it is or what’s the pressure, so I still much rather have no sensor to deal with trading the “inconvenience” of checking the tires once the light comes on, which is what you would do anyway.

I think you’re misunderstanding me. I’m not complaining about the functionality. I think it is good functionality, and I personally prefer iTPMS.

I was explaining why the engineering of the system dictates the information that the interface provides.

And I much prefer this system every time I have to change a tire so not to play the gamble of “will my tpms die before the next change?”. And even if you change them, the chances of an aftermarket one dying and having to deal with that.

I don’t care what pressures the tires have as long as they are good. If I stop to inflate one, I check all of them anyway, with a real gauge. But that’s just me, I know.