Tire pressure gauges, I bought 2 new ones, reading is way off from my old one

Interesting:

 

Now, this begs me a question. How accurate is the TPMS sensor's pressure measurements? Doe they stay accurate for the life of device, say 7-10 years?

 

Being digital, I wouldn't tink low battery causes inaccuracy, just an error for not receiving signal. But if there are any mechanical parts inside of TPMS pressure sensors, then old age may affect accuracy? Or worse yet, are all the TPMS sensors accurate to begin with?

 

Learned something, regarding the stick-style pressure gauge mechanism. Inside there is a spring, and a rubber piston, both of which could wear/fatigue. It seems like my stick-style have always stayed reliable though. Maybe some complacency on my part.

How Tire Pressure Gauges Work | HowStuffWorks

 

I've got old analog gauges, and this discussion is encouraging me to try Tire Assistant, another app from the people who created Hybrid Assistant. Tire Assistant is supposed to display pressures from TPMS sensors (for Toyotas and Lexii only) through a Bluetooth OBD connection.

 

Everything wears out over time.
I would stop by your local tire shop and ask them to check your tire pressure, see what they say it is, then compare it to what your readings are on your new and old gauges. You can be honest, and just tell them, you're trying to figure out if you tire gauges are accurate.

 

Now I'm wondering: does TPMS measure gauge pressure, or just absolute pressure?

Last winter's ScanGauge update showing TPMS values is always waking up in my car with (-14.5) psi -- negative pressure -- which suggests that it is receiving an absolute value and then subtracting a fixed typical sea level pressure. And I'm seeing a negative number because the car has not yet read any sensors, so is starting with a zero placeholder before applying the subtraction.

Tires want gauge pressure, not absolute pressure. So if this is what is happening, then TPMS values will vary significantly more than +/- 1 psi from gauge readings simply due to external barometric and altitude changes.

 

I have the pencil type stick guage (Milton) that I bought right after getting the car. Then I bought the Accutire digital one. There's always a 4 to 6 psi difference. I don't know which one is more accurate.

I like the stick guage for its simplicity, and it's cheap enough to replace often. The digital guage has a battery, and is kept in the hot car all the time. That's probably not good.

 

My several handheld tire gauges (including cheap mechanical pencil type and digital one, somewhat more expensive mechanical and digital one) and also in-line gauge on a few inflator both portable and at gas station are all over the values (± 5psi), I have no idea which one to trust. So, to monitor more accurate tire pressure on my PRIME, I have been using external TPMS like the pic for a few month now. It works great when they are functioning correctly. Comparing the reading of external TPMS to the internal OEM TPMS reading from OBDII using Tire Assistant app, the differences are ± 1psi.It is far better than OEM TPMS that does not display actual number, or phone app via OBDII that can not be used while car is moving. The problem is that those aftermarket TPMS are cheaply made and not very durable. I had one sensor fail only after a few weeks of use and had to return the entire unit. Got new one, but seems to be having some sensor-display unit communication problem again. Since sensors are pre-programed with the display unit and you can not purchase a single sensor to replace a failed one, if one sensor fails, you have to purchase entire unit at ~$50. I was hoping the unit to last at least a few years, but that seems to be wishful thinking.

 

(Photo from ConsumerReports.org.)

How do you know if the battery is low? Does the screen go black? I get a very different reading using this Accutire gauge.

 

Maybe I'm just lucky, but for a while I had a couple of stick gauges and a cheap digital, and they were all pretty close. The one I'm only using now is a solid, made in the US stick, probably will outlast me. The one issue I've noticed is the rubber gasket that presses against the valve stem starts to dry out, get brittle. It'd be nice to have a source for replacement gaskets.

 

Yes, I have no problem with the Milton stick gauges. I have 2 new ones. $6. Just wonder why the big difference in psi when using the digital one. (I think the ACCUTIRE gauge was recommended by Consumer Reports.)

 

This is from Consumers Report about the Accutire Gauge.

Two digital Accutire gauges topped the Ratings, the MS-4400B ($10.99) and MS-4021B ($9.99). The heavy-duty dial-type Intercomp 360060 ($55.95) was also very good but is limited to 60 psi.


Best Tire Pressure Gauge Buying Guide - Consumer Reports

http://www.amazon.com/Accutire-MS-4400B-Pistol-Digital-Gauge/dp/B000G6M3VC/ref=sr_1_2?ie=UTF8&qid=1539996370&sr=8-2&keywords=MS-4400B

 

Ordered MS-4021. Will see how it works.

Posted via the PriusChat mobile app.

 

I'm pretty sure mines Milton too. I'd check but i ate a big plate of spaghetti, pretty much immobile.

Addendum: Yeah mine's a Milton. As I already said, on page 1. Repeating myself.