D2: Retrofit rear brake pads wear indicator system
 

I'll be retrofitting rear pads indicators next time I'll change brake pads.

I always thought that A8s should have brake pads wear indicators FOR ALL 4 WHEELS, not just the front ones -- these are QUATTRO cars after all ! :)

The idea is that armoured A8 D2s came with rear brake pads with wear indicators. Because the same rear callipers were used in armoured and non-armoured vehicles (discs of different diameter but the same width of the discs and the same callipers), the brake pads will have the same geometry as in normal A8 cars, but will come with wear indicators.

Physics: The heavier the car, the larger diameter discs were installed, so that braking pad grabs the disc with bigger leverage, farther from the disc centre, hence better braking efficiency at the cost of faster wear of the pads of course. This is why armoured cars came with wear indicators.

There is retrofit electrical harness in corrugated conduit part number 4D4 971 261 that is designed to fit without having to solder anything. Plug and play into existing wear indicator harness in engine compartment. Connection point D55 in ELSA. There is existing male <--> female electrical connector at point D55. All you need to do is to disconnect that connector and connect harness 'into' the opening, so it'll look like legacy male <--> new female ------ new male <--> legacy female arrangement. Harness then goes to rear axle area under the car and connects to rear brake pads. Electrically all 4 sensors will be daisy chained and connected to the same "bulb" on instrument cluster.

Costs: TPS quotes -- brake pads 4D0 698 451 E: £206.33 (available, but a bit eye watering), electrical harness 4D4 971 261: £53.20 (backorder from Germany).

Pads are still available from eBay sellers (old dealer stock, etc).

http://www.ebay.de/itm/Audi-S8-A8-4D...item3f2ad6852e
http://www.ebay.de/itm/Audi-A8-4D-Br...item3cd43a1d70
http://www.ebay.de/itm/Satz-Bremsbel...item35c3eaef63

Because no one needs those brake pads they sit on shelves for years. I just purchased 4 (!) genuine sets from eBay for £50-80 each from UK and German sellers after some haggling -- (before publishing this post of course) :) Sellers think no one needs those pads, so they frequently appear at low cost. Just wait and grab them -- all good things come to those who wait.

If there are people here who are seriously thinking of adding this feature let me know and I'll do a write up when I finish.


Connection D55:
http://forum.a8parts.co.uk/attachmen...1&d=1384652052

Retrofit harness in a box:
http://forum.a8parts.co.uk/attachmen...1&d=1384652064

Male and female connection to D55 at the bottom of the picture,
two connections to rear brake pads in the background:
http://forum.a8parts.co.uk/attachmen...1&d=1384652078

Cool.

FYI, D3's have wear indicator on the rear. The electronic handbrake measures the pad wear when it closes, eventually putting the brake pad wear indicator on the dash when the travel exeeds a threshold.

Its about the only useful thing the electronic hand brake does.... ;)

Electronic handbrake is smth I'd like to avoid! :) +++

another cool project +++
interesting about the bigger rear discs and caliper further out producing more breaking force. I'll keep that in mind as I was planning to upgrade fronts with RS4 calipers, but didnt want the hassle of installing RS4 rears. Maybe bigger discs on the rear is enough to match RS4 front brakes.

Hi Goran,

Here is the thread (http://as8.ru/forum/viewtopic.php?f=84&t=18998 -- it's in russian, but use google translate) on installing 310mm rear discs from armoured A8 with some pictures. The guy didn't want the hassle of RS4 install, so went this path with a couple of others. He had to use custom made bolts though, so it's not 100% OEM install.

I personally think normal A8 rear callipers and pads look a bit 'sick' on such a large 310mm disc since not the full surface of the disc is utilised. I think it was Audi's 'makeshift' solution for an armoured vehicle. I DO LOVE thought the brake pad wear sensors part of the story +++.

http://forum.a8parts.co.uk/attachmen...1&d=1384798847

http://s47.radikal.ru/i117/1107/a2/09c0eb587591.jpg

Today I managed to retrofit the rear pads wear indicator harness to my D2. It is relatively easy to do if you have a whole day.

The new retrofit harness is inserted into existing harness without having to cut any cables. All you need to do is to trace wire from the front wear indicator that merges with the ABS sensor wiring in a front wheel arch into a single 4 wire harness and then connects to the main car wiring via a 4 pin connector. All you do is disconnect that connector into parts A and B and then connect part A into part A of the harness and then part B into part B of the harness (see the first picture below with Y type of wiring with two connectors).

The connectors can be found of both sides of the car so you will have a choice to run the wiring via the left or via the right side. I have chosen the right side as I had a spare slot in the clamps which hold the 3 fuel lines which run from the nose to the rear. The unused 4th slot was used for wiring. I also changed metal part of the clamps since they were too rusty on my car. They cost pennies.

Pictures!

The front side of the 'plug-and-play' connector
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

which can of course be looped
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

The full harness, about 5m. Just the right size.
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

Rear wheel 1 connector
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

Rear wheel 2 connector
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

Old fuel lines clamp. Notice a spare slot from the left hand side of the picture
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

Rusty clamps changed and the wiring fitted now (corrugated plastic pipe on the right)
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

Connect the new harness to the rear pads wear indicator connector
http://forum.a8parts.co.uk/attachmen...1&d=1433171106

And hide the connector in the recess of the wheel arch
http://forum.a8parts.co.uk/attachmen...1&d=1433171106