tyre pressure OCD and uneven sensor data

[sergey_ja]

hey all. Somewhat of a childish question, but it bugs me.

The car is new, J1.2, 21" Spyder wheels. One tyre - rear left - is always reading 0,1 bar lower than the rest. I've evened them at the gas station numerous times, using the same gauge. You drive it, you park it, it will become 0.1 bar lower again. You can drive it longer, the tires will heat up and it will even, but by this time the other three will add another 0,1 bar and you are, again, left with one showing lower.

The dealer says it is not a leak, but rather a sensor calibration offset feature, which is within tolerance anyway. Are yours the same?

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[whitex]

Are you using absolute pressures of differential pressure display to compensate?

 

[sergey_ja]

Absolute.

and even when it evens out it gives me different suggested pressures.

 

[whitex]

There should be a way to show differential pressure on the instrument cluster (hit the scroll wheel after selecting the left tube).

 

[SoccerMan94043]

I have the same... the side of the car that gets sun first will heat up first and will show higher. At night things normalize typically.

I think that plus when they rounding up to the next number can put things off (you could be .01 below the other tire and it would show as a full 10th of the point PSI difference).

 

[jadatis]

Absolute pressure is the gauge-pressure plus ambiënt pressure, or do you have other idea about it.

The sensors in tyre send digitalised the pressure in one pressure-kind, in steps of 0.5 psi or 0.05 bar.
Temperature also in one kind ( C or F) and in steps of 1 , read once beginning at - 40 degr C/F ( is the same)

The receving unit then substacts a fixed 1.013 bar/14.7 psi average ambiënt pressure at sealevel, and converses it to the other pressure- and temperature-kind, and gives that on screen.

If now one sensor dont send the last digit for pressure, you get a lower pressure receved .

This could be here.
But also it could be by a little inacuracy, and roundings.

On one picture here, I see also recomended pressure given on screen.

Porsche and BMW let this recomended for the setting flow with temperature change. 20 drgrC/ 68 degrF is index-temperature they calculate from to temperature in tyre.
This makes possible to adjust pressure warm at a tankstation.
And mayby,bif they also use it for cold pressure, lesser those anoing " tolow pressure warning" in colder seasons in the morning.

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