Here’s the latest reader question, along with my reply!
Leo asks: This is not really a question. Just a statement of fact. I have a 2007 GMC Envoy with 240K miles, also a 2013 Tahoe with about a 100K miles. Both have tire pressure sensors. The readings on the sensors never agree with the actual readings (with a gauge) and on the Envoy the sensor says Right Rear but the one that is off is the Left Front. I do not rely on the sensors. Nobody should. I don’t know how the sensors are supposed to work. Do you?
My reply: You’re not alone! Would you believe that many of the brand-new cars I test drive have faulty tire pressure sensors, too?
The systems are much more elaborate – pressure is measured (imputed) as a function of wheel speed – so, there are more potential failure points – than a simple mechanical stick gauge, which measures pressure directly.
But, manually. You have to actually get out of the car and check, yourself.
Many people don’t.
Thanks to the Ford Explorer/Firestone tire fiasco of the ’90s, all new vehicles built have the TPMS – to address the problem of people not checking their tires and driving around on under-inflated tires.
Which, in my opinion, has increased the problem of under-inflated tires because many people no longer bother to check the air pressure in each tire manually to confirm the figure is within spec. Many people – me among them – ignore the TPMS warning light in the dash because we’ve grown used to it being a false alarm.
The problem there, of course, is that sometimes it isn’t.
And now we have a new problem. Created by a complex, failure prone (and expensive to fix) “solution” to a simple problem.
Which, of course, is the sort of thing the government does best.
…
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The wife had a rent car and one tire showed to be down. This was right after her Accutire digital gauge had quit and I hadn’t replaced it. It had a guarantee to be accurate to .05 lbs. She spends money at least a couple times trying to air it enough to get the light off. She got home and told me. I took my Milton truck gauge and it showed about 80 lbs. Before the Accutire quit it and the Milton stick agreed.
If you read reviews of tire gauges you’ll find some that are $330. Probably if you don’t race F 1 it won’t be a big deal to use an plain old Milton. Both my truck Milton gauges agree and used to agree with a different style of Accutire gauge. I have nothing bad to say about Accutire gauges since they lasted well over 10 years and I had a Milton truck tire gauge that gave up after about that same length of time.
The great thing about the Accutire gauges is they had their own case and large read-outs and I paid less than $10 for them. I’m sorta anal about tire pressure since a low tire can be the one to come apart on a truck and is always letting the other tire take almost all the load which causes a shortening of that’s tire life also.
I’ve had Dodge trucks showing low pressure but checking them with a gauge showed them to be fine. I had a flat on one and had it fixed. After being repaired it was showing to be low although I had checked it with my Milton. Those sensors, as everyone in a tire shop can tell you, are simply junk. Like all cheap digital sensors, they lie.
The last company I worked for, the boss didn’t want the drivers to waste time so he’d push on a tire with his foot. It if didn’t push in and obviously be flat he’d tell you to go on, even after I would show my gauge.
This crap went on for a couple months and we’d ruin tires left and right simply because they were low and we could run on an overload permit, the very last person in the trucking bidness to need an overload permit. Of course it’s just a matter of paying money to the state. They won’t even know what sort of truck it is being used on.
One day we had a truck go down at the same time the loader did. He’s busy with the other truck so i take the opportunity to get all 18 tires up to 100 lbs(ok, one was only 80). The next load I kept the engine wide open on a certain stretch that up to that point I had only seen a maximum of 62 mph. It was a fairly strong engine and that didn’t seem right on a level road. When I ran the same load on those properly aired tires it reached 72 mph and went over the next steep hill 3 gears higher than it ever had. After that the truck felt like it had gained a great deal of power(it had, in a way). No telling how much fuel he wasted and still does doing this crap.
The wife had a rent car and one tire showed to be down. This was right after her Accutire digital gauge had quit and I hadn’t replaced it. It had a guarantee to be accurate to .05 lbs. She spends money at least a couple times trying to air it enough to get the light off. She got home and told me. I took my Milton truck gauge and it showed about 80 lbs. Before the Accutire quit it and the Milton stick agreed.
If you read reviews of tire gauges you’ll find some that are $330. Probably if you don’t race F 1 it won’t be a big deal to use an plain old Milton. Both my truck Milton gauges agree and used to agree with a different style of Accutire gauge. I have nothing bad to say about Accutire gauges since they lasted well over 10 years and I had a Milton truck tire gauge that gave up after about that same length of time.
The great thing about the Accutire gauges is they had their own case and large read-outs and I paid less than $10 for them. I’m sorta anal about tire pressure since a low tire can be the one to come apart on a truck and is always letting the other tire take almost all the load which causes a shortening of that’s tire life also.
I’ve had Dodge trucks showing low pressure but checking them with a gauge showed them to be fine. I had a flat on one and had it fixed. After being repaired it was showing to be low although I had checked it with my Milton. Those sensors, as everyone in a tire shop can tell you, are simply junk. Like all cheap digital sensors, they lie.
It’s even more perverse than you’ve explained Eric…some cars have a TPMS implemented in software which uses the wheel speed sensors (usually installed for ABS and/or Traction Control), usually to calculate tire diameter from wheel speed and transmission output speed. But most I have come across use an actual little strain gauge type pressure transducer integrated into the valve stem, with a small transmitter or transponder. The TPMS has a receiver or transponder which either receives periodic pings from the wheel transmitters, or interrogates them periodically, waking them up for a transmission pulse. The computenmachine knows which wheel is which by a code in the signal coming from each one (serial number, MAC address, whatever). That’s what makes replacement of a wheel sensor a pain, recoding the uebercomputenmachine in the kraftwagen to recognize the new tire sensor/transmitter. That, and the inevitable damage that comes from condensed moisture in the tire, damage to the stem, some have a battery that gives out after 5-6 years, etc. etc. All to appease St. Joan of Claybrook and St Ralph Corvair.
I have the wheel RPM sensors, vs. any physical measurement and telemetering of data, in my 14 VW Jetta. I find it to work rather well. The two times it has gone off, I had a nail in my tire. So, now I don’t ignore it. This derived method is much better than a direct measurement.
And now we have a new problem. Created by a complex, failure prone (and expensive to fix) “solution” to a simple problem.
Which, of course, is the sort of thing the government does best.
Gov’t could screw up a wet dream!
Hey Mark,
“Gov’t could screw up a wet dream!”
Government, from their perspective, rarely screws up anything. The concept of “unintended consequences” is popular in libertarian and conservative circles, but I think it is mostly wrong. This concept assumes that the architects of a government program are well meaning, but misguided. This is naive, the “unintended consequences are the desired outcomes of most programs, the stated purpose is a smokescreen. Note that the supposed “failure” of any program always leads to more money and control to going to those who have “failed”.
The purpose of minimum wage laws was to render those less desirable unemployable. The purpose of the welfare state was to create a dependent class, destroy poor, mostly black families and to create conflict between racial and economic classes. The purpose of the drug war was to create a criminal underclass that would perpetually scare the populace and to facilitate covert funding for illegal government operations. The purpose of licensing and regulation is to stifle competition and to advantage the connected political and corporate players. The purpose of safety regulations is control and power. The purpose of all of these programs is to weaken what Nock termed “social power” and enhance State power. Of course, the architects also benefit financially.
The great Robert Higgs describes this here:
https://mises.org/library/myth-failed-policies
Cheers,
Jeremy
Well-said, Jeremy!
It took me several years to come to terms with what I now am certain is a calculated, long-term plan to get most people out of private cars by making it progressively more expensive and unpleasant to drive. I know for a fact that the EPA bureaucrats are aware that vehicle exhaust emissions are a non-problem at this point yet purposely exaggerate them (as well as proposed “reductions”) to maintain a crisis/hysteria paradigm that maintains and perpetuates their power.
Even if the proponents of these failed policies and programs were well intentioned in the beginning, they didn’t REMAIN so. How could one continue to promote policies and programs that are obvious, wretched, miserable FAILURES?! After it became obvious that certain policies and programs failed, why were they not terminated? Why wasn’t something else tried?
Exhibit A is American education. I remember back in the 1970s (more than 40 years ago now) seeing cover stories on the main news magazines about how Johnny couldn’t read. If American education was known to be failure back then; if failed policies continued to be promulgated, pursued, and implemented; then, at the end of the day, one can only conclude that they’re DELIBERATE. If good intentions were really at the core of what those in power do, then they would have CHANGED WHAT THEY WERE DOING when it became obvious that their policies were a FAILURE.
Hi Mark,
Excellent points, at best those who cling to “failed” policies display a preference for their own self interest above that of the supposed beneficiary group. I believe that many, if not most, of such people believe that they are doing good. However, the ability of humans to align their self interest with their perception of the “public good” is nearly limitless. This trait, among those who cannot legally wield coercive power, is likely to produce social benefits, as the only way to gain what you want is to satisfy the desires or needs of others. However, among the coercive class, this trait is toxic.
Years ago, I heard Lloyd Bankfein claim that Goldman Sachs is doing God’s work on earth. It is easy to dismiss this as a self serving lie but, what is more likely, and terrifying, is that he probably believes it. The core principle of “coercive collectivists” is that they know better than us mere mundanes. They genuinely believe that they are forging a better world, and that they are entitled to be rewarded for it. Those who believe in “progress”, social engineering, etc.. value an abstract vision of perfection above all else. Necessarily, individuals create an impediment to their goals and need to be controlled or eliminated.
Even the overt racism of the original minimum wage laws and the drug war were not considered immoral by those advocating them. Minimum wage laws were intended to disadvantage Blacks, Asians and Hispanics because they were seen as sub-humans who, because they were willing to live in “squalor”, could out-compete the better class of people. Such rationales were once openly admitted, but are no longer politically acceptable. Thus, a recasting of the narrative was necessary. The genius of this recasting is that policies born in racism, eugenics and social engineering are now seen as policies in favor of the same groups originally targeted by them. Most believe this new narrative, those in power profit from it. Few, even among the architects of such programs, are capable of understanding the essential immorality of their goals.
Kind Regards,
Jeremy
What ever happened to just walking around and kicking the tires ???
(hard to do in sandals, I reckon …)
One of the first things I did with the Cherokee is compare the TPS to a known-good* gauge. I found mine to be in agreement +/-3 PSI, close enough for the girls I go out with. I find that as I run around the mountains it’s pretty important to keep an eye on tire pressure, since it can change pretty drastically with altitude. Airing down for traction also means putting the computer into conniptions, which can be pretty annoying although it only chimes once per start. The quicky-lube place we used to take the work trucks usually under inflated by 4-5 PSI, which sets off the TPS alerts, which was yet another reason to stop going there and just go to the dealer.
*Actually acquiring an accurate air pressure gauge is pretty difficult. If you want one that has a calibration doc you’re going to pay big bucks. Most of the stick gauges you get from the parts store checkout counter are worthless. I have an older digital gauge in the work truck from Walmart that seems to be pretty close.