6 ms·

Also, the info that is exposed to end-users is awful and seems to be getting worse. We have a 2021 Volvo and it has TPMS, but the TPMS info screen on the large

Also, the info that is exposed to end-users is awful and seems to be getting worse. We have a 2021 Volvo and it has TPMS, but the TPMS info screen on the large infotainment display shows /4 orange dots, one on each tire/ when the pressure in ANY is too low. It doesn’t tell you the actual pressures, or what they should be, just that it needs maintenance. My other 2017 Chevy tells me the ~real-time (takes a few seconds to change) pressures of all 4 tires. I know that the Volvo has this info, and a screen more than capable of displaying that info, yet someone chose instead to treat the user like an absolutely helpless idiot and basically suggest that they should stop using the vehicle immediately and have it flatbed trailered to the nearest dealership /because a single tire is a few PSI low/. I understand having idiot lights for idiots, and sure, do that on the dash, but please give end users any way to get some actual info. It’s the “door ajar” when the vehicle knows which door but doesn’t disambiguate to the user. It’s bad design, or malicious design to boost dealer profits.

lern_too_spel 5y ago
The Volvo is using an iTPMS system, which does not have absolute PSI measurements.
- zwily 5y ago
  My Audi does this too. And despite the salesman’s insistence that it’s actually better this way, it still bugs me.
kube-system 5y ago
To elaborate a bit on what someone else said -- some cars with TPMS systems do not have pressure sensors at all. It is possible to add TMPS to a vehicle entirely via software by analyzing other data from existing sensors. For example, it might be looking at sensor data that looks like: Steering angle: 0 degrees LF wheel speed: 305 rpm RF wheel speed: 293 rpm LR wheel speed: 302 rpm RR wheel speed: 285 rpm In this case, it may be possible for the car to determine that you probably have some incorrect pressures, but it may not know exactly which tire(s) is/are wrong. Nor does it know what the pressures are.
- userbinator 5y ago
  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.
  - deleted 5y ago
    [deleted]
  - svnt 5y ago
    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.
    - culopatin 5y ago
      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
      - kube-system 5y ago
        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.
userbinator 5y ago
Incidentally, every aftermarket TPMS does show all 4 pressures too. Some will even monitor the spare as well.
octoberfranklin 5y ago
Unless they are doing some serious wizardry, cars don't know which tire is which. Telling the tires apart was never one of the goals of the TPMS standards. The transponder in each tire just shouts out its serial number and pressure on 315mhz and then sleeps for a random amount of time. The car counts how many times it has heard the various serial numbers, and assumes the top four most frequently heard serial numbers are its own tires (as opposed to those on the car next to it). It is sort of stupidly easy to gather location data from TPMS sensors. If I ran a major criminal gang I'd track the cop cars this way. 315mhz is almost VHF, it goes a long way. One receiver per city block should do it. Covering your turf would be easy.
- chillingeffect 5y ago
  >gather location data from TPMS sensors. That's one of the revelations from Snowden files. Us govt does this!
  - lern_too_spel 5y ago
    Source? I heard of this trick from Schneier, but I have not seen any documents saying the US government is using it. In my experience, 90% of the things people say were in Snowden's documents weren't, so I'm skeptical. https://www.schneier.com/blog/archives/2008/04/tracking_vehicl.html https://www.schneier.com/blog/archives/2008/04/tracking_vehi...
    - chillingeffect 5y ago
      it's been a while but check back in a few days. if i can find it again i'll post it here.
- BenjiWiebe 5y ago
  Ok, first off - a lot of cars do know which tire is which. Most do it by associating certain TPMS IDs with certain tires. This is what the technician is setting when he does a TPMS re-learn (or reset) after rotating your tires. Other vehicles actually know which is which without being told. I'm not sure exactly how this is done, but I'm guessing/vaguely recall hearing they do this by using multiple receivers. As for tracking from a distance - these sensors have very low output power, and a lot of their signal is blocked by the metal wheel. It can somewhat be done but you'll need more than one receiver per block if you want 100% coverage. Sources: worked as a tire shop technician for a while, messed around with SDR, read a lot online. Also: https://web.wpi.edu/Pubs/E-project/Available/E-project-091115-154458/unrestricted/MQP_piscitelli_arnold_2015.pdf https://web.wpi.edu/Pubs/E-project/Available/E-project-09111...
moltke 5y ago
The "check engine" light used to feel like a frustrating but economical decision. Modern cars have multiple full color displays now with computers that have all the information they need to at least display fault codes and still just give you "check engine" style warnings. It's always been this way.
- kube-system 5y ago
  There are lots of vehicles that can display fault codes and other diagnostic information directly through the gauge cluster. Usually they’re hidden in a secret menu. Search “read codes without scanner” on YouTube and you’ll see a ton of examples.
vineyardmike 5y ago
Genuine question: What about if you rotate the tires? (do people still do that?) You would have to reset the data and tell it what tire is where, or it would need 4 antennae for each wheel.

lern_too_spel 5y ago

The Volvo is using an iTPMS system, which does not have absolute PSI measurements.

zwily 5y ago
My Audi does this too. And despite the salesman’s insistence that it’s actually better this way, it still bugs me.

kube-system 5y ago

To elaborate a bit on what someone else said -- some cars with TPMS systems do not have pressure sensors at all. It is possible to add TMPS to a vehicle entirely via software by analyzing other data from existing sensors. For example, it might be looking at sensor data that looks like: Steering angle: 0 degrees LF wheel speed: 305 rpm RF wheel speed: 293 rpm LR wheel speed: 302 rpm RR wheel speed: 285 rpm In this case, it may be possible for the car to determine that you probably have some incorrect pressures, but it may not know exactly which tire(s) is/are wrong. Nor does it know what the pressures are.

userbinator 5y ago
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.
- deleted 5y ago
  [deleted]
- svnt 5y ago
  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.
  - culopatin 5y ago
    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
    - kube-system 5y ago
      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.

userbinator 5y ago

Incidentally, every aftermarket TPMS does show all 4 pressures too. Some will even monitor the spare as well.

octoberfranklin 5y ago

Unless they are doing some serious wizardry, cars don't know which tire is which. Telling the tires apart was never one of the goals of the TPMS standards. The transponder in each tire just shouts out its serial number and pressure on 315mhz and then sleeps for a random amount of time. The car counts how many times it has heard the various serial numbers, and assumes the top four most frequently heard serial numbers are its own tires (as opposed to those on the car next to it). It is sort of stupidly easy to gather location data from TPMS sensors. If I ran a major criminal gang I'd track the cop cars this way. 315mhz is almost VHF, it goes a long way. One receiver per city block should do it. Covering your turf would be easy.

chillingeffect 5y ago
>gather location data from TPMS sensors. That's one of the revelations from Snowden files. Us govt does this!
- lern_too_spel 5y ago
  Source? I heard of this trick from Schneier, but I have not seen any documents saying the US government is using it. In my experience, 90% of the things people say were in Snowden's documents weren't, so I'm skeptical. https://www.schneier.com/blog/archives/2008/04/tracking_vehicl.html https://www.schneier.com/blog/archives/2008/04/tracking_vehi...
  - chillingeffect 5y ago
    it's been a while but check back in a few days. if i can find it again i'll post it here.
BenjiWiebe 5y ago
Ok, first off - a lot of cars do know which tire is which. Most do it by associating certain TPMS IDs with certain tires. This is what the technician is setting when he does a TPMS re-learn (or reset) after rotating your tires. Other vehicles actually know which is which without being told. I'm not sure exactly how this is done, but I'm guessing/vaguely recall hearing they do this by using multiple receivers. As for tracking from a distance - these sensors have very low output power, and a lot of their signal is blocked by the metal wheel. It can somewhat be done but you'll need more than one receiver per block if you want 100% coverage. Sources: worked as a tire shop technician for a while, messed around with SDR, read a lot online. Also: https://web.wpi.edu/Pubs/E-project/Available/E-project-091115-154458/unrestricted/MQP_piscitelli_arnold_2015.pdf https://web.wpi.edu/Pubs/E-project/Available/E-project-09111...

moltke 5y ago

The "check engine" light used to feel like a frustrating but economical decision. Modern cars have multiple full color displays now with computers that have all the information they need to at least display fault codes and still just give you "check engine" style warnings. It's always been this way.

kube-system 5y ago
There are lots of vehicles that can display fault codes and other diagnostic information directly through the gauge cluster. Usually they’re hidden in a secret menu. Search “read codes without scanner” on YouTube and you’ll see a ton of examples.

vineyardmike 5y ago

Genuine question: What about if you rotate the tires? (do people still do that?) You would have to reset the data and tell it what tire is where, or it would need 4 antennae for each wheel.