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Tire Pressure Monitoring System (TPMS) Accuracy

Tire Pressure Monitoring System (TPMS) Accuracy

I was aware that the MX Tires came with a TPMS warning icon on the dashboard if air pressure was seriously low.

I just became aware,by chance,that we can manually access each individual tire'S PSI level, from the steering wheel left hand scroll wheel.

My question is, have you monitored these readings on a regular basis, and how accurate are they?

I have a small hand held digital PSI gauge, that is fairly old, and differs with the MX readings by 1-2 PSI.

Since improper air pressure can affect range, I'd like to closely monitor my levels for a 1100+ mile trip tomorrow.

Thanks everyone for weighing in.

lilbean | 17 janvier 2017

My handheld digital gauge as well as the gauge on my air compressor read 1-2 psi higher also. I'm going with those readings. They both match each other and the reading on the car is lower every time. I trust my handheld digital gauge.

PedanticOne | 17 janvier 2017

Most gauges are off by a bit unless you spend the money on a good one. I'd expect the car to be potentially off a bit.

Be especially cautious of any small hand-held gauge like the tiny ones you see at the counter in an auto parts store. And the ones on a compressor aren't terribly good either.

All this said, they're usually in the ballpark, and unless you can truly feel 1-2 lbs of pressure difference in your tires, or you're racing, it shouldn't matter too much.

PedanticOne | 17 janvier 2017

Here's the one I bought a while back. It has an accuracy within 2%, which is pretty good, and it's not wildly expensive.

https://www.amazon DOT com/gp/product/B000COS8FI

PedanticOne | 17 janvier 2017

P.S. Spam filter is a ball of EVIL.

Saxman | 17 janvier 2017

Thanks both Lilbean & Pedantic

poloX | 17 janvier 2017

but with 1 or 2 psi, who cares?

lilbean | 17 janvier 2017

I do. Lol!

poloX | 17 janvier 2017

lilbean, serious or sarcastic? :o) ) Saxman, no offence but why bothers but good to know though. :o

Saxman | 17 janvier 2017

I'm certainly no expert, but from what I've read 1-2 PSI over/under can affect mileage and tire wear. And, with the mileage I'm probably going to drive annually, it could make a big difference.

Now, I'd like to hear from some of you brainiacs, who can count electrons or who have split the atom...:)

PedanticOne | 17 janvier 2017

1-2 psi will have negligible effect. Especially since, as I mentioned, most gauges are off by about that. When you start to get to 5psi difference, then you can start to realize the effects in tire wear, handling, softness/hardness, 'fuel' efficiency, etc.

Some of it is often personal preference if you want to affect your ride quality or other aspects. On my motorcycles, the manufacturer specs call for pretty high pressures, but I never run anywhere near that. I favor grip over longevity in that scenario.

Saxman | 17 janvier 2017

Good to know Pedantic, I certainly don't want more things to stress over.

poloX | 17 janvier 2017

@Saxman, also, don't measure tire pressure after a long drive either. Measure it in the morning before you get in the car. I always keep the pressure about 3psi higher than what recommended and refill when it gets to about 2 psi below. In the winter, I might want to do 4psi higher and in the summer, maybe just 1-2 higher.

johndoeeyed | 17 janvier 2017

Tyre pressure varies far more than 1-2 psi due to ambient temperature and driving duration and conditions.
1-2 psi inaccuracy in the gauge is the last of your worries.
http://www.tirerack.com/winter/tech/techpage.jsp?techid=73

Saxman | 17 janvier 2017

@Polox
I usually measure in my garage after several hours after driving. Didn't know about higher PSI than recommended, thanks

Johndoe...also thanks

PedanticOne | 17 janvier 2017

The numbers they give you are almost always cold temperatures. And I personally wouldn't set them higher than recommended.

Saxman | 17 janvier 2017

OK Polox & Pedantic, Duke it out so I know which way to go... recommended or higher PSI :)?

lilbean | 17 janvier 2017

Lol polo!

MhoPower | 17 janvier 2017

I checked this on my MX yesterday using a 10+ year-old digital gauge purchased at Costco. The difference between the displayed TPMS readings and the handheld gauge was within 0.5 psi for each of the tires. The readings from the TPMS (when cold) have remained the same (41 psi) since I picked up the car in late Dec. "Buy air compressor and an accurate pressure gauge" is on my todo list as this "is" important to me (no sarcasm intended ;-))

poloX | 17 janvier 2017

BTW, I just accidentally discover a weird feature. I get even lilbean does not know about it yet. :o) If you press and hold the buttons on the left of the steering wheel that is used to skip or replay a song....guess what it does? It switches from USB to Radio. The strange thing is that it only toggles between these 2. It does not switch to stream, inturn, or phone...only these 2???

lilbean | 17 janvier 2017

Ha! I don't use the USB for music, but if I did, I'm sure I would have known. ;-)

georgehawley.fl.us | 17 janvier 2017

Bernie is right. Pressure in a tire is proportional to absolute temperature. Since Fahrenheit version of absolute zero is -460 degrees, to a first approximation tire pressure will increase about .4 psi for every 5 degrees increase in temperature. The temperature of the air in the tires is elevated by heating due to friction and absorption of infrared heating of the pavement when you drive. If the air temperature inside a tire goes from 50 degrees resting in your garage to 100 degrees after you have been buzzing down an asphalt road in bright sunlight, your tire pressure will increase by about 4 psi.

Leeo | 17 janvier 2017

I have an expensive tire pressure gauge since the MX doesn't read in tenths of a psi i'm going to say it's within +/- .5 psi.

Redmiata98 | 17 janvier 2017

I have found the TPMS to be accurate. The pressure will increase as you warm up the tires and the dash gauge changes as the tires warm up. You should assess the pressure in tires that have sat still for at least 3 or 4 hours to get an accurate reading before you add/subtract air.

MhoPower | 17 janvier 2017

Thanks @mrrjm. You just saved me buying a more expensive gauge as that is exactly what my Costco purchased unit told me.

Saxman | 17 janvier 2017

George, mrrjm, Redmiata & Moh...

Great info. This is what's great about this Forum.

Thanks

EVRider | 16 février 2017

I'm late to this party, but I was wondering about TPMS accuracy also and found this thread. I recently developed a slow leak in one of my tires, so I've been keeping the tire pressures displayed on the dash. The TPMS shows pressures about 2-3 PSI below what my hand-held gauge shows; I believe my gauge is pretty accurate. Since others have reported low readings from the TPMS in this thread, I'll assume my gauge is still correct (more or less).

EVRider | 16 février 2017

Didn't realize this thread was in the MX forum, which I don't monitor. If you reply to me, I won't see it unless you post something in the MS or General forum.