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Comment by fmntf | Hacker News Reader

TMPS is mandatory on european cara since 2014

TPMS is mandatory unfortunatly no sensor is needed for that. Here is a good german article about that: https://www.adac.de/rund-ums-fahrzeug/ausstattung-technik-zu...

basically the following vendors only use indirect control systems (no sensor): VW-Group (VW, Audi, Seat, Skoda), PSA (Citroën, Peugeot, DS, Opel), Fiat, Mazda or Honda. the problem with sensors is that a new set of tires have additional cost of 120-300€ which is most often not an issue since the vendors who use direct control systems are mostly premium vendor cars.

Yes. But you can monitor the pressure indirectly without a pressure sensor, by comparing the rotation speed of the wheels. Wikipedia says that a flat wheel has a smaller diameter and rotates faster. https://en.m.wikipedia.org/wiki/Tire-pressure_monitoring_sys...

It's cheap and not great but it's a valid TPMS system for Europe.

The US spec requires detection of deflation independently, so indirect isn’t allowed as underinflating all 4 tires can’t be detected by indirect means.

Honda cars sold in the US use an indirect system that works exactly as he described, so it must be allowed or Honda has gotten away for years flagrantly violating the law.

NB: if you have one of these systems be on the lookout when you get your tires changed; a lot of chains will try to charge you for the tpms sensor when you don’t even have one.

Some indirect systems use the first 10km driven after changing tires as a reference. Those systems can detect all four tires deflating at the same time, however, they need to be explicitly told via a special key combo or a diagnostic interface that you changed the tires just now. Maybe that is what they are trying to charge for.

Nope - they've never even seem to have been aware of that system, never activate it, and they charge per tire.

At any rate, at least on the cars I've owned, it's been something along the lines "hold down this button on your dash for 30 seconds", so I'd be pretty irate about being charged for that even if they did it.

Indirect TPMS does not need radio transmitters like this on the wheels.

Under-inflated tire can be detected using the ABS sensors and software.

https://en.wikipedia.org/wiki/Tire-pressure_monitoring_syste...

Afaik, TPMS does not follow a specific standard for communication. I saw a video about tpms and privacy issues. Because each sensor have a unique id, and beacons it out every minute. With four weels, you have an unique is every 15 seconds or so. The industry response was that it was an unreasonable attack since each car brand had their own protocol. Well, the rtlsdr projects now can decode a dusin. But my point was, that since there is no standard on how tpms should communicate, why would there be a regulation dictating it do be done in a specific manner? The end goal is that the cars drive with correct tire pressure.

ABS speed sensors are sensitive enough to determine tire pressure

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