Tire pressure accurate?

[RickMachE]

Mine reads 2 psi higher than my gauge, 3 psi higher than Discount/Costco’s auto fill thing
It’s odd that some peoples cars take so long to register. Mine updates like every 2 to 5 minutes.

I believe you are incorrect.

TPMS updates when the tires are revolving. That info is transmitted to the vehicle, which then transmits to the cloud, which then updates FordPass. While steps 2 through 4 might be timed, step 1 is controlled by driving.

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[Mach-Lee]

My tire pressure on sync seems consistently high.
This is after sitting in the garage overnight. I filled the tires with my pump that was set to shut off at 39 psi and my separate tire pressure gauge reads 39 psi.
Anybody else have this experience?

Your tire gauge is off by 2 psi.

If you use an accurate digital tire gauge, then the pressures will match.

Pressures will not update until you drive the car afterwards.

 

[ChasingCoral]

 

[ChasingCoral]

Your tire gauge is off by 2 psi.

If you use an accurate digital tire gauge, then the pressures will match.

Pressures will not update until you drive the car afterwards.

Correct. The sensors will not turn on until you reach a critical speed. That prevents the batteries in them from running out too quickly.

 

[azerik]

I believe you are incorrect.

TPMS updates when the tires are revolving. That info is transmitted to the vehicle, which then transmits to the cloud, which then updates FordPass. While steps 2 through 4 might be timed, step 1 is controlled by driving.

I meant while driving. I can understand them not updating while it's sitting.

I believe you are incorrect.

TPMS updates when the tires are revolving. That info is transmitted to the vehicle, which then transmits to the cloud, which then updates FordPass. While steps 2 through 4 might be timed, step 1 is controlled by driving.

I meant while driving. I can understand them not updating while it's sitting.

The OP and I are in the SW, it's been warming up here but here is a graph of my garage temp for a day and a half. Outside it got up to about 98 yesterday and my insulated garage door faces south.
TPMS of my car is still showing the arrival pressure of 43psi from getting home at 8pm last night until I force refresh the app (pull down on the Home Screen of FP)then it shows 39. If it's not cooling off a bunch the tires will stay at a hire pressure. When it was 97h - 75L my garage would also cool off, as long as I wasn't charging.

 

[DoogleMac]

Thanks y’all
it’s been a month since I filled the tires to 39 with the pump. I’ve driven a couple thousand miles since and checked cold tire pressure several times with an accurate gauge.
from all the comments I think we can conclude that the tire pressure is a couple psi too high.

 

[Woeo]

I believe you are incorrect.

TPMS updates when the tires are revolving. That info is transmitted to the vehicle, which then transmits to the cloud, which then updates FordPass. While steps 2 through 4 might be timed, step 1 is controlled by driving.

Then why did mine warn in the middle of the night that it had deflated a dangerous level?

 

[markboris]

Correct. The sensors will not turn on until you reach a critical speed. That prevents the batteries in them from running out too quickly.

To be a bit more specific, the sensor radio transmissions are sent to the BCM about every 60 seconds as long as the car is traveling more than 20 mph. If the vehicle is stationary more than 30 minutes, the sensors go into sleep mode to conserve battery power.

 

[MoonRiver]

Just found out my 22 select has been inflated with nitrogen. They said the green cap on the tire stem indicates nitrogen inside. She indeed has green caps.
It seems that nitrogen holds pressure better the air. The pressure has not been dropping as quickly as my other cars with plain air.

 

[Mac’ Mach e]

Nitrogen molecules are larger than air molecules and are less able to pass out of rubber tires.

 

[Mach-Lee]

Nitrogen molecules are larger than air molecules and are less able to pass out of rubber tires.

Actually, it’s the other way around. The molar mass of a nitrogen molecule is 28 g/mol, and the average molar mass of air is 29 g/mol (air is 78% nitrogen already). Graham’s Law tells us the rate of effusion would be less than 2% different between the two gases, pure nitrogen leaking slight faster than air.

Nitrogen in car tires is a scam if you know basic chemistry. It does not hold pressure better. Dry air is all you need.

 

[Teslaeata]

Think it’s a scam even if you don’t know chemistry ?

 

[azerik]

$500 nitrogen at the dealership.
That should be publicly shame-able. Tomato throwing and the whole 9 yards.

 

[ChasingCoral]

Nitrogen molecules are larger than air molecules and are less able to pass out of rubber tires.

There is no such thing as an air molecule. Air is a mix of various gases and is ~ 78% Nitrogen, 21% Oxygen, 1% argon and small amounts of the rest.

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