BRAKE FLUID
| CAUTION | Brake fluid is hygroscopic, i.e. it has the capability to absorb water and moisture from the air. |
If water has been absorbed, the boiling point will drop, i.e., during high braking temperatures the brake fluid may develop steam bubbles and result in decreased brake performance.
Scheme 21
Over time, brake fluid will darken in color. This is a normal chemical reaction and does not reflect on their quality.
| WARNING | The rubber components of the brake system (boots, seals) do not tolerate mineral oil, gasoline, and cleaning agents! Small amounts on the protective boot or sealing ring leads to a change in the parts and affects brake function. |
BRAKES, TESTING
The wheels are driven by the test stand.
When checking, vehicles with manual transmission should be in idle and vehicles with automatic transmission should have N engaged.
Always observe the test stand manufacturer instructions.
Note. When the ignition is switched off brake control system does not work.
Allocation PR-No./Brakes
The brake system installed in a vehicle is documented on the vehicle data sticker via the relevant PR number.
The vehicle data label can be found in the spare wheel well as well as in the Maintenance booklet.
The following tables show the break down of the affected PR numbers. They are important for the brake disc/brake caliper/brake drum combinations.
Brakes
| Brake System | |||||
|---|---|---|---|---|---|
| Dual-circuit brake system with diagonal distribution, anti-lock braking system (ABS) with electronic brake distribution (EBD). Depending on equipment and construction, also with electronic differential lock (EDL), anti-slip regulation (ASR), electronic stability program (ESP) |
Front Brakes
| Front Wheel Brakes | ||||||
|---|---|---|---|---|---|---|
| Brake caliper PR number | 1LJ | 1LL | 1LK | 1LM | 1LN | |
| Front brake caliper | FN3 | FN3 | FNR-G-57 | FNR-G-57 | FNR-G-57 | |
| Pistons | Diameter mm | 54 | 54 | 57 | 57 | 57 |
| Brake disc PR number | 1LJ | 1LJ | 1LK | 1LK | 1LK | |
| Front brake disc | Diameter mm | 312 (16") | 312 (16") | 340 (17") | 340 (17") | 340 (17") |
| Brake disc thickness, ventilated | Mm | 25 | 25 | 30 | 30 | 30 |
| Brake pad wear limit | Mm | 21 | 21 | 28 | 28 | 28 |
| Brake pads | ||||||
| Pad thickness, new (not including backing plate) | Mm | 14 | 14 | 14 | 14 | 14 |
| Brake pad wear limit (not including backing plate) | Mm | 2 | 2 | 2 | 2 | 2 |
| TT RS Front Wheel Brakes | |
|---|---|
| Brakes PR number | 1LA |
| Front Brake Caliper | Brembo M4 |
| Pistons | 40 / 44 mm diameter |
| Brake disc PR number | 1LK |
| Front brake disc | 370 mm |
| Brake disc thickness, ventilated | 32 mm |
| Brake pad wear limit | 30 mm |
| Brake pad wear limit (not including backing plate) | 2 mm |
Rear Brakes, FWD
| Rear Wheel Brakes, FWD | |||
|---|---|---|---|
| Brake caliper PR number | 2ED | 1KZ | |
| Rear brake caliper | CII 38HR | CII 38HR | |
| Pistons | Diameter mm | 38 | 38 |
| Brake disc PR number | 2ED, 2EE | 1KZ and 1KJ | |
| Rear brake disc | Diameter mm | 286 (16") | 286 (16") |
| Brake disc thickness, not ventilated | Mm | 12 | 12 |
| Brake disc thickness, ventilated | Mm | ||
| Brake disc wear limit | Mm | 9 | 9 |
| Brake pads | |||
| Pad thickness, new (not including backing plate) | Mm | 12 | 12 |
| Brake pad wear limit (not including backing plate) | Mm | 2 | 2 |
Rear Brakes, AWD
| Rear Wheel Brakes, AWD | ||||||
|---|---|---|---|---|---|---|
| Brake caliper PR number | 1KJ | 2EE | 2EA | 2EF | 2EG | |
| Rear brake caliper | CII 41HR | CII 41HR | CII 41HR | CII 41HR | CII 41HR | |
| Pistons | Diameter mm | 41 | 41 | 41 | 41 | 41 |
| Brake disc PR number | 1KJ, 1KZ | 2EE, 2ED | 2EA | 2EF | 2EG | |
| Rear brake disc | Diameter mm | 286 (16") | 286 (16") | 310 (17") | 310 (17") | 310 (17") |
| Brake disc thickness, not ventilated | Mm | 12 | 12 | |||
| Brake disc thickness, ventilated | Mm | 22 | 22 | 22 | ||
| Brake disc, wear limit | Mm | 9 | 9 | 19 | 19 | 19 |
| Brake pad wear limit (not including backing plate) | Mm | 2 | 2 | 2 | 2 | 2 |
| TT RS Rear Brakes | ||
|---|---|---|
| Rear Brake Caliper | CII 41 HR | |
| Pistons | Diameter mm | 41 |
| Rear brake disc | Diameter mm | 312 |
| Brake disc thickness, ventilated | Mm | 22 |
| Brake disc, wear limit | Mm | 19 |
| Brake pad wear limit (not including backing plate) | Mm | 2 |
BRAKE TESTING, FWD
Brake Testing on a One-Axle Roller Test Stand
The brake test is to be performed on a one-axle roller test stand.
If the rollers have a start-up delay, the brakes may lock up (EDL regulation).
Do not exceed a test speed of 6 km/h.
Test stands approved by Audi meet these requirements.
BRAKE TESTING, AWD WITH HALDEX CLUTCH
Brake Test on a One-Axle Roller Test Stand
During this brake test, the wheels of one axle are driven in opposite directions, to prevent delivering power to the other axle.
If the rollers have a start-up delay, the brakes may lock up (EDL regulation).
Do not exceed a test speed of 6 km/h.
Test stands approved by Audi meet these requirements.
BRAKE TEST ON A CONVENTIONAL BRAKE TEST STAND, AWD WITH HALDEX CLUTCH
To test brakes on a conventional brake test stand, proceed as follows
Drive vehicle forward until front wheels are on rollers.
Turn off the engine and wait 3 seconds.
Perform the braking test.
After front brake test, let engine run approximately 5 seconds until sufficient pressure has built up in the brake booster.
Drive vehicle forward until rear wheels are on rollers.
Turn off the engine and wait 3 seconds.
Perform the braking test for the rear brakes.
| WARNING | During the brake test, the engine must not run and the ignition must be off. Otherwise, the Haldex clutch drives the rear wheels. |