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... your brakes stop working altogether and you have to find a nice big tree to run into when you want to stop!<p>You Audi dealer will tell you when it's time for new brake pads. In fact, places like Midas will do a free inspection to determine if you need new brakes. They will even show you your brakes when your car is on the lift so that you can see what a worn brake pad looks like compared to a new one.<p>Brake wear indicators are usually just a very simple piece of metal that hangs off of the pad near the rotor. When the pads wear down to a certain point, this piece of metal comes into contact with the rotor and causes the screetching sound whenever you are moving.<p>I don't think the A4 has any other advanced warning systems about the brakes, unless you consider "brake fade" an advanced warning system.<br>

many brake sensors, and I assume Audi's one but don't know, use an electrical contact to sense brake pad wear... when the pad wears down past a certain point, it wears away the insulator and shorts out [or completes] the circuit, and your brake pad light goes on... Porsche & MB, among others use this.<p>

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Audi does this, but not on the A4s to my knowledge, although I haven't looked at the pads. When the pads are made, they have a wire running through them. Once the pad wears low enough, the wire breaks and causes a short which trips the pad wear sensor. You can see this on many 200/5000/100 (type 44 models).<br>Later!<br>