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TPMS vs hand gauge

Retired Bob

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Retired Bob Enthusiast

Retired Bob

Posted
Posted

Up until my 1st oil change, my TPMS readings (in the DIC screen) and my hand held pressure gauge were exactly the same - I really liked that! After my 1st oil change the TPMS showed approx 3lbs lower than my mechanical gauge on all tires so I asked the dealer service tech to 'relearn'/reset the TPMS - requires a TPMS tool since 2011 I believe. The relearn took less than 10 minutes. The DIC screen still shows the TPMS to be about 3lbs less than my gauge. After researching the subject, it seems many people believe the 'computerized' TPMS uses various parameters to "calculate" the tire pressure but a hand help pressure gauge gives an instant real-time reading - thus the differences.

See: http://www.gmtruckclub.com/forum/showthread.php/54631-Tire-Pressure-Monitoring-System

 

Bottom line seems to be, set your tire pressure when tires are cold using a handheld gauge and then rely on the TPMS shown in the DIC window to determine if your tires experience a sudden drop in pressure. So to keep good tire pressure for long tire life and a good ride I am still using my handheld gauge to check my tire pressure.

Spurshot Senior Enthusiast

Spurshot

Posted
Posted

My 08 LTZ TPMS showed the same as my handheld throughout it's 5 years with me.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Resetting the TPMS does nothing to the accuracy of the sensors, only tells the vehicles in what position the tire is located.

fondupot Senior Enthusiast

fondupot

Posted
Posted

My hand gauge have always been more or less within 1 psi compared to the computer.

vetteboy9 Enthusiast

vetteboy9

Posted
Posted

If all four are off by the same 3 pounds, I would test with a different tire gage, just to rule out the possibility of a fault with your gage.

Retired Bob Enthusiast

Retired Bob

Posted
  • Author
Posted

Took measurements at high noon, in the sun, cold tires (i.e., had not driven in over an hour) in the Charleston, SC area - air temp about 87 degrees. All 4 tires showed 35lbs via TPMS. Using a gauge, I read 39lbs LF, 40lbs RF, 38lbs LR and 39lbs RR. So in the morning, when it's cool - about 70 degrees, I'm going to set the pressure to 34lbs on all tires - hopefully will get a better ride. I have the Goodyear Assurance Fuel Max tires and I'm guessing that 'fuel max' means hard rubber which means I feel all the road bumps. After lowering the pressure in all 4 tires, the TPMS should read in the low 30s.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Have you ruled out that your gauge is not bad yet?

Spurshot Senior Enthusiast

Spurshot

Posted
Posted

Boy, you guys must have a lot of time to waste.

A person should make time for the things they enjoy. LOL

thewhitestallion Senior Enthusiast

thewhitestallion

Posted
Posted

Took measurements at high noon, in the sun, cold tires (i.e., had not driven in over an hour) in the Charleston, SC area - air temp about 87 degrees. All 4 tires showed 35lbs via TPMS. Using a gauge, I read 39lbs LF, 40lbs RF, 38lbs LR and 39lbs RR. So in the morning, when it's cool - about 70 degrees, I'm going to set the pressure to 34lbs on all tires - hopefully will get a better ride. I have the Goodyear Assurance Fuel Max tires and I'm guessing that 'fuel max' means hard rubber which means I feel all the road bumps. After lowering the pressure in all 4 tires, the TPMS should read in the low 30s.

 

not sure if that is true or not but I do know that when goodyear came out with that tire what they did is change the compound material to were it allegedly creates the least about of friction and is a lighter tire. I don't think it is really that "hard" of a tire because they seem to wear out pretty fast compared to other high dollar tire choices but that is probably just a goodyear thing. I never bought into their "fuel max" slogan though.

Retired Bob Enthusiast

Retired Bob

Posted
  • Author
Posted

Well, I went out at 6am today and gauge checked all the tires - 35lbs in each tire. Checked TPMS and it showed 32lbs in all tires. I'll stop at the dealer and have a tech check pressure using their digital gauge and then I'll follow him and see what my gauge shows and what the TPMS reads. Knowing the TPMS reads 3 or 4 lbs low is okay as long as I know that.

 

But, hope I don't begin getting 'notices' on-line from OnStar - "Your left rear tire is low"! BTW, how does OnStar know my tire pressure does something transmit a signal to OnStar? If that is so they must get a ton of info each hour for all the GM vehicles with OnStar.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Yes while you are under the free or paid for OnStar program they download the vehicle data and email it to you in a report.

bass mechanic Enthusiast

bass mechanic

Posted
Posted

They are never accurate where I live because tpms are reading absolute pressure and an external tire gauge reads relative. So we have to subtract 3 psi to get the accurate reading here. Tpms always read 3psi less than actual then measured with an external gauge

 

 

Sent from my iPhone using Tapatalk

spectaculous Enthusiast

spectaculous

Posted
Posted

They are never accurate where I live because tpms are reading absolute pressure and an external tire gauge reads relative. So we have to subtract 3 psi to get the accurate reading here. Tpms always read 3psi less than actual then measured with an external gauge

 

 

Sent from my iPhone using Tapatalk

Huh? External pressure gauges read GAUGE pressure which is the amount in addition to atmospheric pressure. That won't be a 3 psi difference from an absolute gauge, it would be 14.7 psi difference.

 

The TPMS is reading gauge pressure just like a manual pressure gauge does. Any difference you are getting is the difference between two separate pressure gauges'readings. And having a difference doesn't necessarily mean either gauge is correct or calibrated...

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