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.
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
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
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.
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:
Here's one showing a guy using a TPMS sensor programmer tool (about
$150, or much more):
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
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.
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.
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.
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
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.
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.
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
"Shoot them first."
Judges are lawyers, too.
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
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
(Devil's Advocate, movie quote)
Total law school JD (Juris Doctor) enrollment:
"Total J.D. enrollment is now at 111,561".
Total practicing lawyers: 1,338,678
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.
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.
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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