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TPM Accuracy

Boomer AZ

Boomer AZ

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Prescott, AZ
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I’m running on the 19” wheels. Air pressure should be 49psi. Today I used a compressor and digital pressure gauge and set all four tires to 49 psi. I then drove a short distance, until the TPMs registered tire pressure. Readings ranged from 46 to 51 psi. I leaning towards the TPMs being the issue. Comments? Similar experience.
 
Tire pressures do change as you drive them, as warm tires and cold tires will have different pressures (pv = nrt, where p is pressure and t is temperature, so as temperature rises so will pressure)

The manufacturer recommended tire pressures generally assume cold tires, aka “parked for three hours or more, or if the vehicle has been driven less than a mile (1.6 km) at moderate speed.”

Generally “hot” tires will need to be filled to about 4 PSI higher (53, in this case) but you should always recheck them when they’re cold.

It sounds like you’re within range but a little low?
 
All tires were cold, drove maybe 1/4 mile to get reading. Does anyone know the spec accuracy of the TPMs? I’m an engineer, stuff like this drives me crazy.
 
Mine seem to be quite accurate. We have had some large temp fluctuations already so I have had to check a couple times. In addition, swapped wheels and kept existing tpm's and tires and the shop noted they seemed accurate as well. Not definitive but a data point or two.
 
Boomer AZ said:
All tires were cold, drove maybe 1/4 mile to get reading. Does anyone know the spec accuracy of the TPMs? I’m an engineer, stuff like this drives me crazy.
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As an engineer, I completely respect that and have no idea :) now I’m also curious

According to the manual, the TPM sensors are built by Continental Automotive GmbH, model TIS-01, FCCID KR5TIS-01
 
Boomer AZ said:
All tires were cold, drove maybe 1/4 mile to get reading. Does anyone know the spec accuracy of the TPMs? I’m an engineer, stuff like this drives me crazy.
Click to expand...
Many TPMS sensors are specified for +/- 5kPa accuracy or 0.7PSI. Much more accurate than what you are seeing.
 
What a fascinating place this forum is. I had no idea I was intrigued by TPMS until now. But, I’m glad @Boomer AZ is on it and will undoubtedly report back!
 
The TPMS on my car seem to be ok. Our temps have dropped recently and yesterday I used a digital gauge to get all four (19") tires to 49 psi yesterday after the car had been sitting all day in the garage (they were 44-46 psi). After filling them, I drove briefly and verified the car registered them all at 49 psi, and the same this morning. After driving several hours in 70-degree weather today, they all registered 53 psi.
 
Snafu said:
The TPMS on my car seem to be ok. Our temps have dropped recently and yesterday I used a digital gauge to get all four (19") tires to 49 psi yesterday after the car had been sitting all day in the garage (they were 44-46 psi). After filling them, I drove briefly and verified the car registered them all at 49 psi, and the same this morning. After driving several hours in 70-degree weather today, they all registered 53 psi.
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That sounds exactly correct.
 
OK, was an issue between my old compressor, digital gauge and valve stem extender. Old compressor auto shutoff when it got to 49 psi, digital gauge locked on 49 psi. I tried my new Ryobi 18V handheld inflator. It’s digital gauge doesn’t lock in. I’d run the pressure up to 49 psi and take my finger off the trigger, but the pressure dropped back to 46 psi. I was losing 3 psi across the valve stem extender. I than ran the pressure up to 49 psi after I removed my finger from the trigger. Did this to all 4 tires, now the TPMs also read 49 psi for all 4 tires. Mystery solved, TPMs are very accurate, peace and harmony have returned to my garage.
 
Glad you were able to sort it out. I can't get mine to display in the app consistently.
 
Boomer AZ said:
The car has to be going overc20 mph for the TPMs to read pressure
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that makes sense then. I thought you could see the pressures cold as the car was just sitting around.
 
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