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Discussion Starter #1
At an Audi Club track event this week a discussion started about why many people use more aggressive track pads on the front then in the back for A5/S5/RS5 cars. As an example I use Carbotech XP12 in front and XP10 in back Many people on this forum seem to use a similar approach. Why not use the same level of pads on front and back? That is how the OE pads work - similar pad material front and back.

Every car is designed with a brake bias that is designed to address the weight distribution of the car. It would seem that when you use a more aggressive pad on the front than the back you are shifting more brake bias to the front. This means the front brakes are doing more work than was designed relative to the back and this could mean less brakes power and more heat on the front brakes.

Why not use the same level of track pad front and back to maintain the brake bias that was designed into the car?
 

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I will cease to use 12 up front and 10 in the rear. That is once they weAr out
 

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One could argue that the car is designed for less hard braking than what is common on the race track.
 

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Discussion Starter #4
One could argue that the car is designed for less hard braking than what is common on the race track.
So, this would seem to mean that due to the braking requirements on the track we want to shift some brake bias to the front. Have you seen any information that we could review that would say we should shift brake bias to the front for these cars while on the track?

Any track junkies have any other feedback on this?
 

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I have no info for review I'm just speculating.
 

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I'm afraid we are the minority here Rich. Most of these cars do not reach the track.
 

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Pure speculation on my part (as I've never tracked mine and use OE pads etc) but I would assume that as most of the braking is achieved on the front an excessively grippy pad on the rear would increase the likelihood of the rear locking up and inducing a spin under braking. I believe that this is why brake balance tends to be slightly forward as the rears locking is unpredictable and difficult to catch, whereas the fronts locking is more predictable/easier to catch.

As to why 12/10 were settled on perhaps that was something someone established in the past and has become lore? I guess due to the time and expense involved it's not practical to try it with both setups back to back and see what is what?
 

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Discussion Starter #8
Pure speculation on my part (as I've never tracked mine and use OE pads etc) but I would assume that as most of the braking is achieved on the front an excessively grippy pad on the rear would increase the likelihood of the rear locking up and inducing a spin under braking. I believe that this is why brake balance tends to be slightly forward as the rears locking is unpredictable and difficult to catch, whereas the fronts locking is more predictable/easier to catch.

As to why 12/10 were settled on perhaps that was something someone established in the past and has become lore? I guess due to the time and expense involved it's not practical to try it with both setups back to back and see what is what?
Your speculation sounds like it is right on the money based on the below info. And, yes, trying to see if 12/10 is lore or fact/experience based.

Info from Iracing:

Brake Bias
This is an adjustment of the relative amount of hydraulic pressure applied to the front verses the rear brake calipers and pads. This is needed to optimize the braking power, as a car decelerates, load transfers to the front tires, which generally improves their grip, while decreasing the grip at the rear of the car. In addition, the size of the front and rear brake rotors, pads, and piston area is often different requiring different amounts of pressure for the same braking power. The goal is to adjust the proportion of the braking forces between front and rear (brake bias) in order to maximize overall braking efficiency. If the brakes are still applied as the car turns into the corner, the brake‐bias setting will also have an effect on the car’s turn‐in balance.

Tuning advice:
Maximum braking performance occurs just before brake lockup, as a sliding tire has less grip than a rolling tire, thus tuning brake balance is all about controlling when the brakes lockup. As max performance obviously will occur when all 4 tires (& associated brakes) are doing the maximum work, an ideal brake bias is one that locks the front and rear brakes at the same time. In practice however, locking the rear tires typically result in a rapid spin, and locking all 4 wheels results in a slower spin, especially if the car is trail braking. For this reason, some “extra” front bias is normally used [already built-in from the factory - RR], because when the front brakes lockup the car remains stable (but you lose the ability to steer the car – it just goes straight - UNDERsteer) and this allows the driver time to recognize the brake lockup and reduce brake pressure to regain max braking performance and control. To tune the brake bias, pay particular attention to what happens during the braking phase and corner entry. Sudden spins in this zone often indicate rear brake lockup, while a bad push may indicate front brake lockup. Video replays or data acquisition systems can be useful in identifying this, but remember the inner (unloaded) tire will be the first to lock.

Increasing Front bias: Increasing brake bias to the front will put more braking force into the front tires. This will stabilize the car in braking zones and increase understeer at corner entry. The compromise is that with too much front bias the rear tires are being under‐utilized and overall braking efficiency will suffer. This can also cause rapid front tire wear due to front tire lockup, especially of the inside tire which is the first to lock up.

Reducing Front bias: This puts more braking on the rear tires, which, within limits, improves braking efficiency. Too much rear brake bias, though, hurts performance in two ways. First, it reduces overall braking efficiency. More seriously, too much rear brake bias, particularly if the driver is not braking in a straight line or has weak footwork on downshifts, can cause the rear tires to lock up, which puts the car in a dynamically unstable condition that can easily result in loss of vehicle control. Note that with a moderate amount of rear‐brake bias, the car will have a tendency to rotate (OVERsteer) at corner entry upon brake release.​
 

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I can give you a reason based on my recent experience.....I tried purchasing Front and Rear Pads for Track use (Hawk DTC-70) but they only offer Front Pads

I'm new to tracking my car so I figured that this might just be the way it is


Sent from my iPhone using Tapatalk
 

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From my track experience on 2 wheels, heavy braking from high speeds means that the weight transfer takes 98% of the braking force to the front of the bike and indeed many riders do not use the rear brake at all, or use it just to steady the bike and/or to slide the rear end into a turn. A bike always has 2 massive discs upfront and one small one at the rear.
 
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