037

So yesterday I was parking and I was scraping over everything while trying to park...figured I just didn't have enough clearence and went to sleep.

Woke up, got into the car, started, and got a TPMS light that pressure was low left front tire @ 25psi. No problem, got my trustee pressure gauge and went to investigate, all other tires were showing 30 or more.

So...front left was at 20 PSI and everything else was in the range of 20-25 PSI.

My car was in service on Thursday at an Acura Dealership which was very insulted when I gave them a bad survey.

Well, I pumped up all tires with a tiny compressor in the middle of PA under rain in my business attire.

Then I proceeded to call my dealer and left a voicemail for my service adviser to set an appointment for Monday.

Then, for better or worse, dealership called me (10 minutes later) for a satisfaction survey on Thursdays service...

Long story short, I told em I'm gonna rip the tech's head off when I get there on Monday as I was drivingn fairly aggressively the day before at 30% below recommended low speed tire pressure.

Rant aside - did anyone ever have all 4 TPMS sensors off by this much?

My little pressure gauge is a little round thing that you push in and that moves arrow to a #.

It was also confirmed by my little compressor so I'm 100% positive that TPMS in the car was wrong and not my little gadgets.

---end of rant.

white05rl

I realize you tried two different devices to check tire pressure, but I still bet TPMS is right. Most tire pressure gauges are notoriously inaccurate. Your best bet is with a digital pressure gauge. Some like the Accutire unit: http://www.amazon.com/Accutire-MS-40.../dp/B00080QHMM have an accuracy rating of 0.5psi.

037

well, I've been using these two highly non technological devices for over 2 years and they have never been off by more than 1 PSI vs TPMS.

I'll update once I take the car to the dealer and see what they say.

HEAVY_RL

iTrader: (1)

Its funny you posted this, the guy that services my car was giving me crap because all of my tires were 5 or so over... I check the TPMS regularly and told him no way.

Sure enough all three gauges he had were 5 off from the TPMS.

037

well, I honestly hope that my devices are off but that still would not explain why TPMS was showing 25 on front left tire 2 days after I got the car back from service.

friesm2000

iTrader: (4)

there is also something called accuracy of the sensors themselves, that one might be going bad

037

well, part of the service was updating the computer on the RL, I am leaning towards that being one of the ways they could have screwed things up. As things stand right now, my front left sensor is 10PSI off. Every single TPMS sensor currently on the car does not allign with the two devices I generally use.

Here's a photo of one of them:

friesm2000

iTrader: (4)

you know those are cheapie gauges... like the one in the photo was what like $2 or something

then the compressor gauge, they never get decent gauges, especially those tiny compressors (assuming the one that you can toss in the trunk, and runs off of 12v/cigarette lighter)




also you say the computer was updated, what one was?

037

yes, the computer was updated due to the cold issue that some members on this forum have experienced.

As far as cheapie gauges, there are simple items that just work regardless of cost, like a compas for ex.

Measuring pressure does not require much technology.

Sort of like using an electric thermometer vs one with mercury in it.

I paid $5 for my little pressure device and as I said before, it's never been wrong or disagreed w/ TPMS until now.

Come to think of it, I might have it for over 5 years...no parts to break, no batteries to die...the final word will come on Monday from the dealer.

friesm2000

iTrader: (4)

not really because the part that actually has to measure the pressure, has to have a specific spring rate to it (a copper like tube, when you open the gauge up), otherwise the gauge will be off; it also has to match the scale on the front too

and if you really think about it temperature can effect those gauges also, where the tpms sensors are not, or affected to a different degree



and this cold issue, not sure what you mean exactly, but figuring it's for the ECU (engine/trans) and not the tpms system

037

yes, the issue is ECU and not TPMS. Now, if I had to guess, all the techie devices use the sample pressure mechanism as my device, tach on an LCD screen and charge 10x more.

Bottom line, we will see which device is right tomorrow.

friesm2000

iTrader: (4)

think that is what you mean...


anyways completely different mechanisms to measuring pressure

techie devices use piezoelectric sensors (needs power btw)
http://en.wikipedia.org/wiki/Piezoelectric_sensor


where your gauges use a bourdon tube (the circular tube that attaches at the 6 o'clock position, goes clockwise, and ends at the 2 o'clock position)(also brass instead of copper for the material)

http://en.wikipedia.org/wiki/Pressure_gauge

037

in this case I'm not off by 0.5 PSI but by 10 PSI. I don't think it matters which device I use as long as it's accurate, and as I said, that will be determined tomorrow.

No sense in trashing a cheap device until proven wrong.

my money is on the el cheapo device.

here's the 2nd device, I think this one uses electro something...maybe

vtr1000sp2

Good luck with the dealer but about your gauges, do you know of a tire shop in your area with a calibration setup? The regional Pirelli bike tire dealer here has a setup he hauls to the track which (when I attend), I bring all my gauges to check threshold. I've only ever been .5 psi off with my cheap gauges, dead on with my accutire digital, and dead on with my longacre 4" dial gauge (damn thing better work for $200)

rtr

yea most gauges are incorrect! they give you a very close number but every time you try a new one it says a different reading. you trust the TPMS because it is in the tire and they are all the same. One thing i love about the CANADA model is that the tpms is measured in KPA whitch is more accurate!! You guys should try finding a guage that is digital in kpa that may help. When my car is off by a few kpa's i can feel it pull.

Have you ever seen 2 thermometers with the same number? it's very hard to find! same shit

037

I personally don't care if a gauge is 1 psi off, we're talking 5-10 here. Anyway, dealer looked at car, said left front tire low, after inspecting it twice they found a hole and pluged it. Said nothing wrong with the sensors.

No mention of the fact that when I dropped the car off the tires were in the 35-40 range according to TPMS.

The only way to see what's up is when I take my el cheapo gauges to the car and compare them against TPMS.

If they match up perfectly then the dealer is essentially covering up their act, if not, I will be buying new tire gauges.

friesm2000

iTrader: (4)

we got tenths of a PSI, to bring it within the same accuracy range (if you can find a gauge that reads it though)

037

got AccuTire digital gauge today and confirmed that TPMS matches. Old gauge trashed.

vtr1000sp2

You're gonna love the gauge, cheap and effective.

friesm2000

iTrader: (4)

, so the very "basic" gauges can go out of spec/range


(and even digital gauges can get out of range though, not as often or as easily as a mechanical gauge though; especially if ever dropped or what not)

037

yes, I guess after 5 years of use at $1 per year it did go out of spec.

friesm2000

iTrader: (4)

can't completely complain about that though



and now next time, you know you could easily be looking at an out-of-spec gauge

037

I had checked with 2 gauges that never showed wrong before for a good number of years plus it occured after an ECU update. I had my doubts.

either way, I got my car out of service w/ a hole in one tire. They kept the car for 3 days, enough time to spot a tire that lost 5psi.

db22

Consistancy is what you need, as long as it reads the same every test you can add more if you want more.
BTW I seem to remember the TPMS sensor calibration in the dianostic menu.