Tire Pressure Paranoia?

Do those of you who have full-up tire-pressure monitoring find yourself becoming obsessed? My 2018 OB Touring has the detailed pressure readouts
and it is _way_ too interesting. My old 2008 had the regular warning light for tire pressure and that was it and I checked the tires maybe every 2-4 weeks and got along fine. Now that I know what the pressure is in each tire all the time I seem to be adding air or releasing air weekly as the ambient temperature changes. I even notice when driving that the tires on the "sunny" side of the car rise in pressure more than those in the shade. Probably the only fix now would be the addition of an option for the car to manage its own tire pressure and to leave me out of the loop.
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It's up to you to define the range in variance of pressure from the recommended pressure. Whether something tells you all the time or you keep rechecking yourself using a digital pressure guage, the instruments can't help whether you're obsessed or not.
Checking every 2 to 4 weeks is obsessive unless you know you have a slow leak. If you're losing several PSI every month, maybe it's time to start replacing the tire valves. They're cheap. Tire pressures will vary by about 2% for every change of 10 degrees F. Driving ups the temperature due to the heat produced by the changing flex in the tire for the contact patch. Recommended tire pressure is listed on the decal on the driver's door. Do not use the maximum pressure listed on the sidewall of the tire. However, an underinflated tire will flex more which means it is fail sooner. When measured cold, refill before there is a loss of 5%. 2 PSI doesn't sound like much except a tire has a decent volume of air inside of it (and why those piddly mini-piston air compressors take so damn long to up the pressure in a tire, even for just a couple PSI).
TPMS (Tire Pressure Monitoring System) sensors were required after 2008 due to the TREAD Act (Transportation Recall Enhancement, Accountability, and Documentation act) enacted in 2000. TPMS isn't required to activate an alert icon in the dash until tire pressure is *below* 25% of the manufacturer's recommended tire pressure (so they won't alert when consumers overinflate their tires). To me, that's too much leeway. Since tire pressure, when inflating, is measured with the tire "cold", and because tire pressure increases when the tires are used (driving), a quarter less of pressure seems a bit high. When using the tires, the pressure will go up, so the 75% minimum threshold is farther away.
There are 2 types of TPMS: indirect and direct. Indirect doesn't measure tire pressure. Instead it measures the anti-lock brake system's wheel RPM to detect if one, or more, tires are rotating faster than the others. The underinflated tire has a slightly less circumference making it spin faster to maintain the same RPM as for the other tires. Indirect TPMS has a large margin of error. I did not research which type of TPMS is used in your car.
You said Touring for the model, but not if for the 2.5i or 3.6R engine (and parts might differ). All I did was a search on "tpms" at oreillyauto.com, put in 2018, Subaru, Touring, and selected 3.6R, and later changed to 2.5i. The TPMS they showed there are the next type described: direct.
Direct TPMS actually measure the air pressure, and are accurate to within 1 PSI. A wireless remote gauge is mounted to the inside of the wheel or to the inside of the tire valve. That means there's a battery in the gauge. You can still replace a leaky tire valve stem since that is in the stem outside of the gauge component. The CR2032 coin cell batteries are obvious a chemical device, so they go weak over time. Expected lifespan is 5 to 10 years (that's quite a range difference) or 100K miles.

https://www.youtube.com/watch?v=Znwg8uZBufI

I doubt you'll find shops that will replace the battery, plus they'd be charging for the labor time. They'll just replace the entire wireless remote gauge assembly. The part will cost $65, or more, at the parts shops, and a hell of lot more at the dealerships. You need to replace all of them at the same time, plus there is the labor charge for tire removal, gauge install, tire install, and balancing. TPMS replacement can run from $450 to $2000, and you're doing that every 5-10 years.
Consumers often don't realize there is a maintenance cost to TPMS, just like owners of those hybrid cars don't realize all those gas savings are eaten up by having to replace the LION battery every 5 years adding $1000 to $6000 to the 5-year cost schedule for their oh-so-efficient hybrid car. For Toyota Prius, battery replace costs $2400, and that's before adding in the labor cost. A Subaru XV Crosstrek hybrid battery will cost $4500 (dealer cost), and that's just for the part, no labor. Consumers rarely calculate the TCO (Total Cost of Ownership) over, say, 5 years when choosing a car. Then later they get the nasty surprise. Don't know (well, haven't searched) if anyone has done a survey on the cost of LION car batteries, even with recycling, to see if consumers are actually saving any money and the effect on the environment.
Another problem with direct TPMS is that you can register only one set of TPMS sensors at one time with the car. Some folks run 2 different sets of tires (either swapping the tires, or having them on wheels so the swap is just replacing the tire+wheel instead of going to a shop to put different tires on same wheels and get a rebalance). You might have one set for summer and another with snow treads for winter. When you take off the set with the registered TPMS, the dash light comes on to bug you. Having to install another set of TPMS sensors in all 4 alternate wheels+tires can get pricey, and adds to the cost of those winter set of tires.

https://www.youtube.com/watch?v=Zz_GkSunSZg

That's one way by disabling the TPMS gauge light. His technique is pretty much like putting black tape over the light. There probably is a guide on how to reset the TPMS to register a new set in your winter tires. The following shows how on a Forester:

https://www.youtube.com/watch?v=hTSDgbWoyJY

Here's one showing a guy using a TPMS sensor programmer tool (about $150, or much more):

https://www.youtube.com/watch?v=3-NgKSCousA

He uses the tool not only to program a replacement sensor, but get the ID (from the old one). This guy scanned the old sensors (so their batteries had to be okay), and programmed the new sensors to clone them to look like the old ones. No having to register the new sensors with the car.

https://www.youtube.com/watch?v=bsW1YU4dgo8

You need the tool (the Matco here costs $250) to scan the TPMS sensors and have the car relearn the IDs for the TPMS sensors. After the sensor scan, you use the ODB port to program the ECU to recognize the sensors. You'll have to do this reprogramming every time you switch from your summer to your winter tires, and visa versa. A pain, and you'll need to by a TPMS tool. Maybe there's a way to do it with the buttons in the car, like on the steering wheel, but I didn't bother looking that up.
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On 1/12/2020 8:16 PM, VanguardLH wrote:

I've been telling my wife that the light coming on in her 2008 Forester is probably due to a low battery. We have been monitoring pressures and they are fine. She had one replaced a while back and dealer soaked her for about $200. She won't do that again.
My new Crosstrek has the 4 readouts and I assume exact tire will not be known when they rotate them.
PITA that the government mandated them. Doubt this has done a lick for safety but it has increased repair costs.
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On 2020-01-13 12:17 p.m., Frank wrote:

The government has mandated a few things that make repairs considerably more expensive. And I recently saw a story that there is a push to make LED and/or HID lights illegal. Perhaps even to the point to forcing owners and/or manufacturers to retrofit lights that are not as bright.
OK, I don't like being blinded when someone comes at me with their high beams on, or just badly aimed low beams, but I also really like to be able to see where I'm going on darker roads.
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On 1/13/2020 12:48 PM, Darryl Johnson wrote:

One of my big gripes - government should not legislate science or technology. I read that only 5% of our congressmen have degrees in science or engineering.
The main reason we are prospering today is from getting rid of excessive government regulations.
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Same for judges making decisions on technologies they don't have a clue about. I still remember the judge ruling on Sue, a T Rex fossil, and claiming the fossil remains are considered land (so the gov't could win their case about them managing tribal lands in trust). Guess all those corpses buried at grave sites become the property of the cemetery land owner, too. Uh huh.
Seat belts were also mandated by law. Wearing the seat belts became another mandate by law.

First shoot all the lawyers.
Joke: A group of terrorists burst into the conference room at the Ramada Hotel, where the American Bar Association was holding its Annual Convention. More than a hundred lawyers were taken as hostages. The terrorist leader announced that unless their demands were met, they would release one lawyer every hour. Alternate version: A group of terrorists hijacked a plane full of lawyers. They called down to ground control with their list of demands and added that if their demands weren't met, they would release one lawyer every hour.
Shoot all the lawyers
https://www.youtube.com/watch?v5rErQtJ6uA

Red Heat
https://www.youtube.com/watch?v=h50ZsEHCJ9s
"Shoot them first."
Judges are lawyers, too.
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On 1/13/2020 2:59 PM, VanguardLH wrote:

Actually two of our sons are lawyers. Fortunately neither work on issues where I might agree on this. I have other lawyer friends and relatives and before I retired I had worked with several patent and environmental lawyers. You need good lawyers to protect you from bad lawyers.
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See, lawyers are everywhere. Everywhere! They're like cop families: granddad was a cop, dad was a cop, uncle was a cop, so sons are cops.
"There are more students in law schools than lawyers walking the streets." (Devil's Advocate, movie quote)
Total law school JD (Juris Doctor) enrollment: "Total J.D. enrollment is now at 111,561". (
https://abovethelaw.com/uploads/2018/12/Total-Law-School-Enrollment.png )
Total practicing lawyers: 1,338,678 (http://www.abajournal.com/news/article/lawyer_population_15_higher_than_10_years_ago_new_aba_data_shows )
The script writer for the movie was wrong, except there's more lawyers getting pumped into the system every year (JD takes about 3 years, but there are graduating classes every year). Takes 8 years to become a dentist (4 years for bachelor degree, 4 more for dentistry).
Just seems like they're everywhere. Only contact I've had with them was as a juror and probate court (an jurors are as technically uneducated as are judges). Walk into a law library. You see maybe 1 row of a shelf for state and municipal law. A couple shelves for federal law. The rest of the library is filled with case law (because it's all about citing judicial opinions).
Lawyers fuck up all the time. For example, when they screw up the paperwork for probate, they charge you again to retry, and that might still not be correct, so another stab and another fee. I thought Sales folk pushing software updates and charging for bug-only fix updates (no feature updates) were greedy. No wonder folks in Software Dev & QA distrusted the folks over in the Sales department. They were never in our luncheon crowd. Yes, they are necessary since I like having a salary, but often the picyune fees were unconscionable, especially for OUR software that was defective by OUR fault but obviously not what the customer intended to PAY for in the first place.
Sorry, the shirt we sold you has the wrong-sized buttons. They're too big to fit into the button holes. For an upgrade fee, we'll send you the correct buttons. Sorry, the buttons upgrades we sent were the wrong color (bright pink instead of black). For an upgrade free, we'll send you the correct color. Sorry, the thread used to sew the shirt has been found to degrade after 10 washings, so the shirt will fall apart. For an upgrade fee, we'll send you better thread. Sorry, the shirt sleeves are different lengths. For a fee, we'll send you a set of safety pins to shorten the overly long sleeve as a workaround.
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On 1/13/2020 7:38 PM, VanguardLH wrote:

I see that there are 4 times as many scientists and engineers than lawyers. MD's number 1.1 million. Congress is 75% lawyers.
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The TPMS sensor is a wireless device. Doesn't matter where on your car they are positioned, only that they be within range to get scanned. Rotating the tires is still using the same set of registered TPMS sensors inside the tires.
It is when you replace a TPMS sensor that it has to get registered to the car, or when you want to use a new set of sensors because you swapped between your set of summer tires+wheels to your winter set.
For a 2008, even if bought new, that's too old for the coin cell batteries inside the TPMS sensors. They're rated for a lifespan of 5 to 10 years. Your wife's TPMS sensors are 11 years old (actually older since they were manufacturered and stored before eventually getting installed into the wheel of your choice to put on the car).
I mentioned some costs for getting a dealer to replace the TPMS sensors. Unlikely they will dismantle the TPMS sensors to replace just the battery, and instead will replace the entire TPMS sensor with a new one. That means you pay more by having to buy a whole new TPMS sensor for each wheel. A car shop might just replace the batteries and save you the cost of buying new sensors, but that depends if the TPMS was designed to be dismantled, plus the car shop will very likely charge you a lot less than the dealer for both the hourly labor rate, rebalancing the tires, and can use much cheaper aftermarket TPMS sensors.
If you check the pressures regularly, you don't need the TPMS scheme. It's for the majority of boobs that drive cars and do no maintenance or monitoring of their vehicles, like running the car until the engine oil is filthy, never topping off the fluids, and the only job they do is to refill the gas tank because they have to. There are lots of those drivers. They could never identify the parts for which the fan belt(s) will rotate, assuming they even know how to identify a fan belt.
My cars are old. No TPMS nonsense. I keep a digital pressure gauge in the glove box (a combo tool that also has a seat belt cutter and flashlight). It's up to me to maintain my car, not the car nagging me to do maintenance. I've yet needed to use the low-fuel dummy light since I watch the fuel gauge, just like I watch my speed, and engine temperature, and everything else that I'm responsible for. The TPMS crap doesn't relieve the car owner from maintaining their car, anymore than the Eyesight system relieves the driver of responsibility for actually driving the car.
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On 1/13/2020 12:17 PM, Frank wrote:

I discovered after a few experiences that the TPMS on my 2008 OB was susceptible to outside interference. After having the light coming on several times while driving down the same stretch of interstate in WV and after checking the pressures each time and having them be perfect each time I simply started ignoring alerts in that area. Maybe a coincidence but the big FBI complex is located off to the east of the highway a few miles away. Not having radio frequency analysis equipment readily available I can't say if that is connected but it does seem odd.
As for having to reset the system after rotating tires that seems to be unnecessary on my 2018 OB Touring. I was concerned about that. The explanation given by the technician at the dealer was a bit vague but he said that the new system was smart enough to sense which tire was which by its rolling speed and to reprogram itself to know corner it was in after a tire rotation. I know that mine were not reprogrammed as I watched a tire rotation from start to finish and after a few miles of driving the pressure readings were correct.
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