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Tyre Pressure Sensors

Discussion in 'A3/S3/Sportback (8P Chassis)' started by willmac, Feb 24, 2010.

  1. willmac
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    willmac Member

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    [Feb 24, 2010]
    I am just wondering if someone can confirm how the Tyre pressure sensors work ?
    Reason I ask is that I have seen conflicting info, some saying it is from a sensor in the wheel and other information that it reads from the driven hub itself based on radius size of rotation ?
    The reason I ask is that I specced it on new car without really thinking too far ahead, so changing the wheels from standard 18" up to 19" BBS wheels would render the system defunct if it reads from sensor in OE Wheel.

    I did receive one response already to this question as part of another post, so apologies in starting a new thread but am just curious. I suppose I must have thought the system worked by magic !!!
    Note to self to check how things work before ordering the next time :yes:
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  2. waqi
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    waqi Member

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    [Feb 24, 2010]
    Interesting question.. I don't think they use sensors, or we would have seen the sensors in the OE alloys. If it's based on tyre speed, should be easy to retrofit I would imagine.. (This is the part where I wait for a genius to come along) :readit:
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  3. Khufu
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    Khufu Well-Known Member

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    [Feb 24, 2010]
    On the current A3 the ABS measures the distance per revolution of a wheel & if it changes from when you pressed the SET button it will warn you. Changing the size of wheels wont matter as it will 'learn' the values when you set it plus technically the rolling radius should still be the same.
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  4. neil-A3
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    neil-A3 Member

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    [Feb 24, 2010]
    I have it specced on mine, as far as I am aware, if you change your wheel size it would think that you have a puncture in the tyre, you just press the button to reset to new size as you would when you chage the pressure.

    As far as I am aware it is part of the ABS and can be retroffitted easily, the swich does not cost alot and VAGCAM can change to activate it.

    Mind you dont trust it as mine didn't register a puncture in mine till it was too late, drove on the trye a little too long and the puncture couldn't be repaired, not best pleased as only done about 2K miles.
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  5. Khufu
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    Khufu Well-Known Member

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    [Feb 24, 2010]
    It can be retrofitted but some cars may need the ABS controller changed to support it.
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  6. willmac
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    willmac Member

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    [Feb 24, 2010]
    Cheers guys, making me feel a whole lot better with the responses here so far.:icon_thumright:
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  7. aristides
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    aristides Member

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    [Feb 24, 2010]
    I retrofitted TPMS to my car (cheap enough i might add) but nothing impressive. Just a bit of security when driving along.

    The A3 has no sensors, the button just resets the values and then it starts to "learn" while you drive.

    And what Khufu said :)

    Easy to retrofit, took me around 1 hour to lay the 1 cable i needed from the ABS controller through the inside of my car + the button and some wiring
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