When you buy the OE pads, it includes the above wear sensor already clipped into place. If for some reason it gets damaged you can buy it separately and just clip it right in.

The design looks exactly like that for a BMW - I used to buy them separately when using non-OEM pads and rotors. I'm pretty sure that what actually happens is that as the pad wears the sensor gets closer and closer to the rotor. When the pad is at the wear limit the sensor contacts the rotor and completes the electrical circuit, setting off the warning light.

https://parts.audiusa.com/p/Audi_201...0698151AF.html



https://cimg0.ibsrv.net/gimg/www.aud...a7b0cc2397.png

That's for the 314x25 mm rotor version. There is another version of pad set for 338x30 mm rotor with Parts# 8W0698151AD which does not include the sensor. The sensor itself cost $80.
https://parts.audiusa.com/a/Audi_201...M/1321380.html

Hard to see which version of rotor is on which car. Even after I gave my VIN to a dealer site to look up parts. They still listed both version of front brake pad sets as applicable to my car which surely not.

Weird - both sizes are listed as applicable for my '17 PP Quattro. As you said, it can't be both. $74 for a wear sensor is crazy. For my old M5, for which prices were always very high, they're $28 OEM)

(if you want to see how they fit, at least for the 314mm rotor, start at 6:38 of

(Hmmm - unlike every other forum I use based on this software, I can't uncheck "Automatically embed media". It also doesn't seem to respect "start at xxx time" in the URL)

)

Thanks for the video! Guess I will have to measure my rotor for the proper pads when the time comes to change them.

The video was great, unfortunately it is for the earlier series cars. The US spec B9 have the 4 piston front calipers so the procedure is probably different.

These are definitely different from the last 4 C-series (S6/A6) cars I owned. On those the wear sensor was molded into the pad and there was one on both the driver and passenger sides. I typically do my own brakes and the older C-series had calipers very similar to the ones in the video. On the A6 you did not have to remove the caliper carriers to remove the disk. That was in the instructions but I found that you could sneak the old one out and the new one on with the caliper carrier in place. Another hint - you don’t need to bang on the braking surface to break the rotor free. The best way is to take a 16 oz hammer and give the disk a couple of hard wacks on the center hat. While this seems counter intuitive because you are pounding the rotor on rather than off the hammer blows break the rust bond and the rotor will come right off. This way you do not damage the rotor in the event you want to have them turned,

There don’t seem to be any You Tube How-To’s on our cars brakes yet. Who wants to make one? Maybe one of the guys who tracks their car and changes pads a lot could do the rest of us a favor and create one. There is no rush, I have at least another year on my pads. ;)

Can you run without the wear sensor?

Yes, they can be bypassed by simply connecting the two wires leading up to the sensor. I think somebody posted it above. The sensor is merely a piece of wire embedded in the pad, that at certain thickness starts to get worn through and eventually interrupts the circuit. Once the circuit is open the warning light on the dash comes on. I have aftermarket pads on my RS5 and the rear pads don't have a sensor, which is very common for aftermarket pads, so I have the rear sensor bypassed at the moment.

Thanks @superswiss !

2018 Audi A4 Quattro Premium Plus
 

New to the whole Audi thing. Can anyone tell me how many brake pad sensors come on my Audi and which wheel(s) they would located? I haven't messed around too much with my whole brake system yet, but I've been hearing this little squeak starting to sound every time I brake, regardless of climate/weather. It may be time for a change.

Thank you!