Replacing your brake pads and discs is one of the easiest jobs to do at home on your driveway. It’s one of the first things I ever did working on my cars, and I’m happy to say working on my 2013 Audi S4 is still pretty simple. This guide is specifically for the S4 as it has slightly upgraded brakes to the standard A4, but since it’s still a standard sliding caliper the information can be easily translated to your setup as the process is the same.
The first thing you’ll need to do is jack up the corner you are working on. Make sure to use the jacking point, in my case it’s a section of exposed side sill. Jack the car up enough to fit a jack stand under, and to get the wheel off the ground. While you are unlikely to be under the car at any point here, it’s still good practice to have a jack stand keeping you safe.
Then take your wheel off. You might need to press the brake pedal or let the car down slightly so the wheel is just touching the ground to get the bolts loose. If you have an impact gun definitely use it!
Once the wheel is off you can remove the metal spring clip supporting the brake. You can squeeze it so the lip in the center moves out of the hole its in, then pull it away. Next is the caliper bolts. There are two on the back, 13mm if I remember correctly, that you need to remove, then you can press on the caliper to push the piston back into the housing, then the caliper lifts off.
The rear pad is physically clipped into the piston so you’ll need to pop that out, and the nearside caliper does have a pad wear indicator you’ll need to disconnect the connector on. The outer pad is friction fit with a little dimple. A tap with your ratchet handle gets it to drop out easily enough.
Next, use a bungee cord to hold the caliper up so it’s not hanging on the brake line. You don’t want to fatigue the line at all so support it well. Then it’s onto the two 21mm bolts holding the caliper bracket in place. You’ll likely need a breaker bar to get these loose, so turn the steering wheel to full lock right so you can get the breaker on. Crack them loose, then remove them and the bracket.
Finally you can remove the screw holding the disc in place. It’s a T30 Torx, and if you have an impact wrench I highly recommend you use it as it makes getting these little buggers out so much easier. Once it’s out the way you can lift the disc off of the hub and it’s onto fitting the new bits.
If you are installing a new disc, make sure to use some brake cleaner and wipe it down. They come coated with a thin film of oil to stop them rusting, but you don’t want oils near your braking surface so give it a wipe. Then the disc goes on the same way it came off, fitting ideally a new retaining screw. Then the caliper bracket goes back on, the torque spec for these is 196nm, or as tight as you can humanely get them.
The caliper itself is next, clip the brake wear sensor into the top of the inboard pad, feed the wire through the top of the caliper, then clip the pad into the piston. Put the second pad in place too, slotting the dimple on the back into the hole in the front side of the caliper, then place the caliper down onto the bracket. You’ll need to put the slide pins on the backside in a little to get it to seat, with the ears of the pads hanging on the rails on the bracket. The manual says you should replace the two bolts you removed from the caliper, fitting new ones to 30nm. In my case I’m using some medium strength threadlocker and getting them tightened down to more like 40nm.
Don’t forget to reinstall the metal spring clip too. It’s a pain, but needed. It’s pretty much the same process to getting it off, line it up and use your hands to compress it, then push the central tab into the hole and tap the edges in. You can then fit your wheel back on making sure to torque your wheel bolts to 120nm in a star pattern.
When it comes to the back, first off make sure your handbrake is off so the caliper isn’t seized on, then remove the two 13mm bolts that hold the caliper in place. Again compress the piston back in so you can lift the caliper up. I found unclipping the brake line from the grommeted clamp makes it easier to move around, then you can again support the caliper with a bungee cord or resting it on something solid. The pads come off with a little persuasion. If you do need to replace the rear disc, much like the front there are two bolts holding the bracket on. According to the manual those are also meant to be replaced, and tightened to 100nm + 90 degrees when being refitted. And again the brake disc has a screw holding it on that you will want to replace.
Finally you can fit the new pads, they slide into place in their guide rails, with the outboard pad needing to have the bottom side go in first then it slides in easily. The caliper might be a tight fit to get it back on, I had to… persuade it.. With a rubber mallet and some pry bars, your mileage may vary. Once its on, again the manual says you should replace the two bolts that hold the caliper on, tightening them to 35nm.
And that’s it. It took me about three hours to do all four corners, and flush my brake lines, and film this so it’s easily a single day job even for a novice.
