How to get Brembo 18z brake calipers (from the Audi Q7, VW Touareg and Porsche Cayenne) onto your Audi A4 (B6/B7)
[ This post is incomplete – installation guide and additional images to follow ]
Most of this information will also be relevant to other VAG (VW/Audi Group) cars so if you want 18z’ees on your Golf then this will probably help you too but might not cover the specifics or unique issues presented by your particular model.
You will need:
- A pair of Brembo 18Z calipers
- Mercedes ML500 v8 discs (with modified centre bore)
- Brembo 17Z brake pads
- Brembo 17z/18z pad fitting kit
- Audi Q5 (8R) front brake pad wear sensors
- Custom 17Z/18Z bolts with sleeves
- Audi RS4 (B7) front brake lines
(All items linked to where they’re cheapest on ebay – you’re welcome!)
Parts in detail
Brembo 18z Calipers
The 18z caliper is a big, modern, and proven caliper designed and manufactured by the braking system Gods themselves, Brembo. It’s an excellent upgrade from most stock brake setups (and the fact they look really cool also helps).
The 18Z caliper for the Q7, Touareg and Cayenne applications all sit forward of the wheel hub. On the A4 they will sit behind and so we need to change some things when sourcing calipers from these vehicles. Each caliper has 6 pistons (“6-pot calipers”), 2 of which are much smaller. This smaller pair of pistons is designed to aid even pad wear and should be the first pair to meet the disc as it turns into the caliper. When mounted forward of the hub this smaller pair are at the top, rearward of the hub they should be at the bottom.
In order for the bleed nipples to remain at the top of the caliper and for the smaller pistons to meet the disc first we need to flip over the caliper link pipes and bleed nipples. This is really straight forward so don’t be scared to do it yourself. If you’re having your calipers refurb’d or powder coated, let them know you want the pipes flipped over before-hand and they’ll do it for you. In all cases I’ve seen the powder coater has coated the calipers with the link pipes in place and you don’t want to damage the finish swapping things afterwards. When tightening bleed screws and link-pipe nuts be careful not to over-tighten, they need only a light nip up (this the professional torque term).
Each calliper is marked “18ZR” and “18ZL” to denote which side it should be mounted. Putting the 18ZR on the left side would technically fit, and the nipples would be at the top but the smaller pistons would be the top pair and the last to meet the disc as it rotates into the caliper, which is wrong. Just be mindful of this and check the markings, pistons and link-pipes for correct orientation before installation.
ML500 345mm x 32mm Discs
After a lot of research I chose to use the Mercedes ML500 V8 discs because they were the perfect width, offset and reasonably affordable. They are not quite as big as the 18z calipers can accommodate (350mm potential) but still comparatively massive against the standard audi discs. The only issue is the Audi hub is 1mm larger than the Mercedes and so an extra 0.5mm is needed to be machined off the disc centre bore, making it a total of 1mm larger.
I ordered my discs from Mtec and they modified the bore for me. I also had them drilled and grooved and added the optional black protective coating. Obviously this coating wears off the actual braking surface but protects everywhere else from rust and other road crud. All-in with the modification and optional additions I was looking at around £120. Given that my B5 RS4 brake discs cost £150 EACH this seemed like a total bargain. For what you get and not having to worry about modifying the centre bore yourself, it is a bargain!
We’re putting 17z pads in our 18z calipers because the ML500 345mm discs are a little smaller diameter that what the 350mm’s 18z’s would usually use. The 17z pads give us a great contact area with the ML500 disc and none of the over-hang we would have got if using 18z pads, plus they’re cheaper too.
17z and 18z pads fit exactly the same so the fitting kit is the same too. I bought a Porsche Cayenne (2002>2010) brake fitting kit specific to Brembo 6-pots.
Pad Wear Sensors
This took a little trial and error to get right. In the end Audi Q5 sensors are what worked. They have the correct male connector, they’re long enough with enough wire connecting the two sensors that they can plug into both pads with no tension on the cable.
Don’t be tricked (like I was) into thinking Touareg 17z wear sensors will work. While they’re long enough and fit the calipers nicely the connector is female so won’t plug into the A4’s loom which is also female. Go for the Q5 (8R chassis) sensors and you’ll be fine.
Audi/VW 17z/18z mounting bolts & locking nuts
The carriers for the standard A4 calipers are threaded themselves and the standard bolts screw into this tread, the 18z calipers do things a bit differently. The Brembos have smooth, unthreaded mounting holes, like the hub itself. This means two things, firstly the new bolts will need to be longer as you’ll be using a locking nut to secure them and secondly, shims are required to reduce the size of the caliper mounting holes and prevent any movement of the caliper on the new bolts. You can buy a bolt kit which includes everything you need for around £35. There were some cheaper kits around but for a good quality set that will last, £35 was reasonable.
I experimented a lot mounting everything up to the hub in various orders and could not get everything together with the bolt heads facing outwards, which would give the most clearance. In my case I found I had to mount everything up with the bolt heads facing inwards on the hub and screwing the 55m bolts in they ended up fouling the disc. I shortened each bolt by about 4mm with the angle grinder and filed it smooth to get the clearance I needed.
Tools required for Brembo 18z installation on B6/B7 Audi A4/S4/RS4
Assuming you’ve read the post “Removing B6/B7 Audi A4/S4 front brakes” and already have your calipers unbolted and hanging up out of the way, congratulations! It’s time to fit your new brakes!
Here’s the tools you need:
- 21mm socket (1/2 inch drive)
- ratchet (1/2 inch drive)
- adjustable spanner
- 11mm open-end spanner
- 14mm open-end spanner (depending on your new brake lines – HEL braided lines required 14mm)
Not essential but highly recommended:
- 11mm brake line spanner
Brembo 18z installation guide
This article has been published early. While the installation procedure is still to come, I thought the specifics on the parts required is useful enough to warrant publishing it ahead of completion.
Got questions? Leave a comment. I only know the details of doing this on an A4/S4/RS4 but I’ll do my best.