how does it work and what does it do???? :confused:

got one and noticed that one of the tyres is slightly flatter than the others yet i have had no notice of this! i would of thought it would of let me know

do you mean TPM?

same thing. kinda

TPM doesn't measure tyre air pressure directly, it measures and compares the rolling radius of the tyres by using pulses from the ABS sensors. How flat a tyre would need to be for it to be detected as flat I don't know. I suspect it would need to be very flat. There is information about the system in the owners handbook supplied with the car even if the car isn't equipped with the option.

TMT

You also need to set it so the car knows what is normal.

Get the tyres all to the correct pressue and then press the set button.

nice one, cheers.

Remember that it is unable to detect low tyre pressures if they are uniform and develop over time. As all tyres leak air, after a sufficient amount of time you'll have four flats without the system alerting you - as mentioned, it uses the ABS sensors to determine the individual rotational speeds of each wheel (wheel radii I expect it couldn't care less about actually). When you get a flat or a quick leak in one tyre, the system will notice that that wheel turns slower and sound the alarm, but if all tyres leak about the same amount, the ratios between their roll speeds will remain unchanged and the system won't react.

At least this is what my dealer told me, right after he said they had added this option without my ordering it (production error, but to my advantage for once). I suspect however that there's more to it, if his explanation holds then I don't see the use for the set button. Guess I have to read the manual to find out

Quick thought:

Is this something that can be 'enabled' if not factory fittted using VAG-COM?