Get 400 ? Front Axle, Anti-Roll Bar, Dampers and Steering -> 400 ? 2.7 Brake discs Guide for Audi R8 2 Door Second Generation (2016-2024)

400 – Front Axle, Anti-Roll Bar, Dampers and Steering

400 – 2.7 Brake discs

It is highly recommended that the brake discs and pads are bedded according to

the instructions issued by Brembo (see below). Bedding should prevent the

creation of cracks in the discs and pads and increase the durability. It cannot be

guaranteed that shorter versions of the bedding procedure will produce the

same level of safety and service life of brake discs and pads.

Bedding (source: Brembo Bedding Procedure V1.6)

In contrast to normal organic materials RB330, 340 & 350 show a different

behaviour during the bedding procedure, characterised by very high initial mu

that decreases to a stable level (a bit lower than the first stops). No

modifications in bedding procedures are needed moving from standard organic

pads to these ones; the bedding is mainly useful for the preparation of the disc

rather than the pad material. For ideal bedding, we suggest a phase with a

progression of constant pressure stops (#35 - 40) at increasing speed avoiding,

as much as possible, rapid deceleration. This procedure helps to build a uniform

and stable transfer layer that will subsequently ensure the correct friction; in

this phase the pad material is not modified but works to create a deposit on the

disc surface. (This is the reason why pre-bedded pads are not as useful as pre-

bedded discs). Then, a few high energy stops (#4, 5), at higher deceleration, are

needed in order to stabilize the transfer layer and to promote a repeatable

friction profile during use.

Step 1

Check the disc before use, in particular, the surface conditions (roughness,

damages, geometry) and be sure that the fixing of the disc corresponds to the

manufacturer’s drawing (out of plane, float, etc.)

If the disc is used, it will probably be covered by a transfer layer from previous

usage, we suggest, if possible, to clean it (sandpaper above FEPA 600, brake

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400 – Front Axle, Anti-Roll Bar, Dampers and Steering

cleaner or similar) in order to avoid contamination during bedding. Normally,

this operation can be avoided because the RB330, 340 & 350 friction material

are initially very abrasive and able to clean up the disc surface automatically,

though time-to-bed will likely increase.

Step 2

The bedding is a very critical determinant of the life of brake components. An

incorrect or hasty procedure could compromise not only the life but also the

performance of components, especially brake discs. The bedding procedure is

needed essentially to prepare the disc for the race, so the processes involved are

the same if it is made on the track (GT, formula, NASCAR, etc.) or on the road

(Rally, where we suggest to bed on tarmac), it changes just the time. In order to

prevent unpredictable heat transfer on disc surface (uneven disc overheating),

and subsequent thermal deformation (cracks, vibrations) the bedding should be

achieved by application of groups of constant pressure stops (for a total of #35-

40 stops or alternatively 35 - 40 km of mileage) with gradually increasing of the

initial speed (and total brake energy). These brakings must be made well below

the tyres’ adhesion limit (50 - 60 % of the max race pedal pressure) in order to

achieve a corresponding gradually increasing of torques and temperature to the

brake system and promote a regular third layer deposit, the brake cooling must

be such to avoid overheating of the system (air ducts can be closed a bit, max 20

%, if disc temperature is too low). The maximum speed should be defined by the

track/road conditions and car features. During this phase the mu starts high

(0,8 – 0,9) and then decreases till the stabilization level, initial discs

temperatures can reach value close to 500 - 550 °C (*) (a bit less for pads, see

graph). Only at the beginning brake dust could be visible as normal consequence

of the initial bedding process. At the first stops, when the mu is still very high

(typical for RB340-RB350) and the disc/pads matching not yet optimized, the

heat transfer on disc could be uneven with small disc areas at high temperature,

despite the low energetic level of the brakings. At the beginning of the bedding

too strong brakings (high deceleration) must then be avoided, that could create

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400 – Front Axle, Anti-Roll Bar, Dampers and Steering

local overheating on the disc and subsequent distortion on it. The heat

transferred into the disc becomes however higher (high gradient of

temperature) toward the end of the bedding because the disc surface is now

completely and uniformly settled up and the friction efficiency optimized, at this

point no risk of uneven heat distribution and distortion should exist.

Step 3

After the constant pressure brakings and the subsequent layer formation (step

2) a series of #4 - 5 high deceleration stops are desirable in order to set up the

layer and guarantee a correct functioning. To ensure that the bedding has been

done properly a homogenous, dark and slightly shiny layer must cover the

rubbing surfaces of the discs (the observation of the external surface is enough).

Darker stains are allowed and close to the fixing of the disc there may be visible

purple colored areas (indicating spike temperatures above 550 °C, see picture).

Narrow grooves (imperceptible to touch) are admitted, they will not affect the

performance in use. If the disc is too bright the bedding is not completely

finished, and a second and shorter procedure must be done. Pad appearance

should not indicate any mutation except a higher polishing of rubbing surfaces,

too rough surfaces (cracks, crumbling, detachment) could be caused by an

erroneous bedding, with too high thermal gradients.

* A simple way to check the correct temperature after bedding is to use thermo-

paints that turn white when the temperature is reached. Brembo offers a kit

including 3 paints: red up to 630 °, orange 550 ° and green 430 °C (p.n.

02.5711.10).

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400 – Front Axle, Anti-Roll Bar, Dampers and Steering

Temperature evolution** (sx) and friction profiles (COF vs. speed) during bedding.

** The time is only related to the brake application, it does not refer to the cooling.

Typical appearance of a correctly bedded set of disc/pads (sx) compared to a new one.

Blanking

Attention

Due to thermally induced mechanical stresses, cracks can develop despite

perfectly bedded brake discs and pads. A critical value for the magnitude of

these stresses is the minimum temperature of the brake discs at the beginning

of braking – especially at the end of a very long straight. Subject to circuit

layout, it is therefore necessary to partially blank the brake cooling air ducts.

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400 – Front Axle, Anti-Roll Bar, Dampers and Steering

Attention

In the majority of racing series’, it is not permitted to use blanking on the

exterior of the bodywork (e.g. using tape on the cooler grille). The blanking

must be made on the inside of the car (see Image 19).

2/3 open

1/3 closed

Image 18: Front Axle Brake Cooling Duct

Without Blanking

Image 19: Front Axle Brake Cooling Duct

With Blanking

IR temperature sensors can provide information about the critical, minimum

temperatures when in operation.

Brake disc temperature paint can provide information about the maximum

temperatures of the brake discs. The Audi part number for a kit (AP Racing),

containing three colours, is V03 862 443 E.

The brake disc temperatures are in the correct operating window when:

Green > 430 °C turns white completely

Orange> 560 °C the majority turns white

Red

> 610 °C slight colour change – at the edge of the brake disc friction

area

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400 – Front Axle, Anti-Roll Bar, Dampers and Steering

Crack on the edge

Critical cracks (deep, long, straight and

continuous, cracks on the edges of the

brake discs)

Uncritical cracks (thin, short and

branched, distributed evenly over the

entire surface, no cracks on the edges

of the brake discs)

Attention

Check the brake discs regularly for cracks and replace if necessary!

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400 ? Front Axle, Anti-Roll Bar, Dampers and Steering -> 400 ? 2.7 Brake discs for Your Audi R8 2 Door Second Generation (2016-2024)

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400 ? Front Axle, Anti-Roll Bar, Dampers and Steering

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