How does the Tyre Pressure Monitor system work?

[Bratty]

Just wondering where does the system fitted to the A4 get its signal from?
If I fit aftermarket non audi wheels do I need to disable the system?

Dunk

[ScottyUK]

In the US they have the system where in the valve stem is a monitor and transmitter for each tyre.

In Europe we have the long in the tooth system. The car has sensors on each wheel so the ECU can see if they're locking up, etc (i.e. the ABS sensors). Effectively these can tell the car how many rpm each wheel is doing. If one of the wheels doesn't match for a continued period (a brief wheel spin etc won't affect it) then it'll will flaf up the TPMS.

Basically it works on the theory that a lower pressured tyre has a smaller diameter therefore it will be going around quicker than the other three.

[Bratty]

Cheers Scotty for that info.

Dunk