Information about braking


Dixcelbrake

EK9.org Member
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Apr 16, 2008
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282
Before I start trading on this forum, I would like to put up some useful information here so everyone can understand the Braking system more before buying any aftermarket Brake disk/pad.


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What is Friction Co-efficiency?
One of the important elements in the evaluation of brake pads is “friction co-efficiency”. Friction co-efficiency represents the degree of friction between two objects, note the smaller the figure is, the smaller the friction between the objects are, i.e. the objects are easier to slip, while the larger the figure is, the bigger the friction is, i.e. more difficult to slip. Simply friction co-efficiency can be explained like this, to move an object of 100kg horizontally, it takes a force of 100kg, while if the object is moved by a force of 50kg, the friction coefficient between the object and the road surface is 0.5. In the case of brakes for vehicles, friction coefficient is calculated using braking torque generated during braking (G deceleration) and fluid pressure (pedal pressure) required for generating the torque, the formula for the calculation is as follows,

Normally, normal pad friction coefficient is around 0.3~0.4 and that of sports pads is 0.4~0.5. If the friction coefficient is high, that means light fluid pressure (i.e. light pedal pressure) can produce a lot of braking force, however if the friction co-efficiency is too high, it causes jerks making it difficult to handle. The most important thing about friction coefficient is how fast the friction co-efficiency of the brake pad builds up to its maximum after the brake is applied. The Pads are deemed inefficient if this process takes a long time, this is generally described as having low initial bite (braking force).

The second most important thing is it does not get affected by temperature. Normally, friction coefficient tends to be low when the brake disc temperature is low or extremely high. If the friction coefficient is low at low temperatures, the brake pad will not generate enough braking force in street driving conditions; if it is low at high temperatures, it will cause problems on racing circuits. Efficiency at high temperatures for so called racing pads and ones with stable braking force from the start line to the goal is regarded as of good quality.

The third important thing is the stability against change of speed. It is deemed too dangerous and thus cannot be put on the market if the friction co-efficiency is unstable at the speed of 180km/h even if it braking is stable at the speed of 60km/h. We, brake pad makers, are doing our best everyday to develop materials which retain a stable and high level of friction coefficient in any circumstance. We always aim to present the best performance compound by combining a variety of materials including well-known elements which are used to enhance or stabilize the friction coefficient such as steel fiber, copper, glass fiber, Kevlar, carbon, ceramic and titan.

What is fade resistance? (Anti-fade stability)
“Fade resistance” (Anti-fade stability) is measured by (1) how high the fading point (temperature) is, (2) the difference (drop) between friction co-efficiency before and after fading. Fading is the phenomenon that friction co-efficiency of brake pads sharply drops when resins used in friction materials discharge gas (vapor) beyond a certain temperature which makes a thin layer between the pad and the rotor and causes them to separate. Normally the fading point (the temperature where fading starts) is set at around 300℃~350℃ at an OEM pads, while that of sports pad is around 400℃~700℃ (Fading points vary depending on each material or the way they are used). For sports pads, fading rate (**) is set as high as possible to keep a stable friction coefficient even after fading starts.
Normal pads’ fading rates are around 40 ~50%, whereas those of sports pads are set around 60~80% to maintain friction coefficient at the same level as that of normal pads before fading. We, sports pad makers, are working hard everyday on research and development of composition and content of resins used for the pads and other fibrous materials.
** It represents difference in friction coefficients before and at fading with friction coefficient at fading presented in % against friction coefficient before fading as 100%,

Abrasion of pads (Pads wear)

It is often said that sports pads wear away faster than normal pads but this is correct and wrong at the same time. That is because the degree of abrasion (wear rate) of brake pads varies much depending on the temperature they are used at. The graph below compares degrees of abrasion (wear rate) of normal pads and two types of sports pads (our material M and material Z) when they are applied with 0.4G braking at 80Km/h a thousand times at different temperatures. As shown in the graph, abrasion of pads increases parabolically against temperature, and the higher the temperature is the higher wear rate is. Abrasion of the normal pad is very small when used at 150℃and under but, at 300℃ and over, it could go up more than twice the abrasion of the sports pad. However, as normal pads start fading at 300℃ and decay to a practically unusable degree, there would be few users who might experience the intense abrasion at such a temperature range for OEM pads. For sports pad, while a high temperature range, 250℃~600℃, which they are often exposed to in winding roads and/ or circuits is paid more attention, the wear rate at lower temperatures is higher than that of normal pads. To conclude, for normal road use only, sports pads wear faster than normal pads do, while they last longer when used for winding roads and circuit and excellent with safe braking ability.

The characteristics of aggression to the brake rotor

Most brake pad makers put the braking performance first and characteristics of attack to rotor second or third. As we have released a numerous rotors and offered support to races in a number of categories, we have a good understanding how much rotors affect not only braking force but also anti-abrasion capacity, anti-fade stability and anti-judder capability. Therefore, at our company, when we are carry out research and development we also take into account rotor attack characteristics. Why, then, are brake pads with strong rotor attack characteristics a problem? If brake pad with a strong rotor attack characteristics is used, it scrapes the rotor significantly and the rotor could be turned into something like a LP record. In such a state, the sliding surface is so rough it causes a dull response of the brake pedal. In addition, as it becomes impossible to keep a normal balance, judder is also caused. Additionally, as the rotor surface is now like a file, it cuts into the pad and removes the friction material thus the pad and rotor attacks each other, which in turn shortens the lifespan of the pad. Due to the thinning friction material and the rotor, the brake system itself becomes heated up easily, and so eventually become prone to fade.

Heat conduction

This may not be unfamiliar to most of you but it is a very important aspect in comparing the efficiency of brake pads. Friction materials consist of a variety of materials and steel fiber is one of them. Steel fiber is suitable for enhancing the pads’ performance and stiffness but too much of it causes not only stronger rotor attack characteristics but also higher heat conductivity which puts the surrounding parts under excessive heat. Some of the typical heat harms are -

●widening of calipers 
●distortion of rotors
●fluid leakage from bleed screw
●cracks 
●jagged surface rotor 
●too much wear of pads
●peeling phenomenon due to curving of the backing plate 
●brake fluid vapor lock

These are all very dangerous phenomenon which could immediately cause crash on circuits. High braking performance is particularly expected from racing pads and so contains a large quantity of steel fiber. However, that causes the pads to be heat conductive and also to heat up easily. We have succeeded in developing a race pad with low heat conductivity by using as little steel fiber as possible.
The name of the pad is R01. Please experience it with your car this excellent performance cannot possibly be shown in data.

The life of the Rotor

If you think you do not need to change the rotors, then you have danger right in front of you. Rotors have a lifespan and in the case of the front rotors, about 1.0mm wear on one side. * i.e. 1.0mm wear on either side of a rotor, inside or outside. In the case of the rear rotors, it’s 0.5~0.75mm wear on one side. The minimum thickness is indicated on each rotor (Please be careful as the minimum thickness is different depending on part number). Use beyond minimum thickness is very dangerous because of the lower heat resistance. In the worst case, rotors could be distorted or cracked easily. We do recommend you to change rotors before such things happen.

What is the Heat treatment process?

At our company, a strict temperature control is being implemented. Detailed information on duration and temperature cannot be made public due to corporate confidentiality; however, we are going to use some imaginary figures for explanation. First, raise temperature by 5℃ every 10 minutes and, when the temperature reaches 300℃, keep heating for 8hours to maintain the same temperature. After that, cool it down lower the temperature by 5℃every 10 minutes. On a graph, it is easy to see the temperature control is ideally done. Heat treatment basically takes 24 hours for the whole process. By taking as long as 24 hours, and by carrying out heat treatment slowly keeps perfect control on the temperature, distortion is avoided, the binding of metal particles is reinforced and precision in heat resistance is improved.
* The cited figures in the temperature changes in the heat treatment are imaginary and so different from the time and temperatures in our actual heat treatment.

What is the heat resistance temperature of disc rotors?

Unlike brake pads, it is very difficult to indicate the exact temperature i.e. “ ~℃”. Original rotors and basic materials for all types, SD type or HD type, are at the same risks of cracks or distortion when temperatures becomes beyond 600℃ or higher, however, cracks or distortion do not always happen if temperature goes over 600℃ depending on each condition of use. The affecting elements depend on as how fast it was cooled down, how often the temperature was repeated over 600℃ or how the state of the brake system including caliper was, are often more important.
 

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rvm

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thanks for sharing this information, sticky!
 





moon*

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Mar 19, 2008
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do any one knows stock ek9 rotor can withstand up to wat temp??
 



moon*

New Member
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ehm.. since the EK9 STOCK rotor is kinda made for tracks, i m guessing it should be alrite to enter tracks right?
 


RagingAngel

本田 Gearing Authority
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Mar 26, 2008
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It's more than fine. Even cheap crap $30.00 rotors will work well for most HPDE and even full blown sprint race use. They're disposable items, I don't see a reason in spending too much on rotors unless it's an endurance event, or you're looking to reduce the rotating mass with a 2pce option.
 


Dixcelbrake

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Apr 16, 2008
Messages
282
A good quality disk can last alot longer than standard or low quality disk. OEM disk and Dixcel normal plain disk both made by Grey cast iron but OEM disk is using grade FC100-150 but our Dixcel normal plain disk is FC200-250, so they are alot stronger than OEM disk and also with some additive, it can keep the disk temperature lower than OEM disk. By having lower temperature around the braking area, it can help the caliper seals, brake oil, caliper, suspension damper...etc last longer and thats mean you will have less chance to have a brake failure or high temperature causing problem with common lower ball joint, melted caliper seals problem.

When you use the car on the road, you might not be able to tell much different between different brand Plain disk, We have tested our race car on track been thought lots of problem with overheated brake system before like having Brake hoses overheated and blew up on track under braking, melted caliper seals causing oil leak, boiling brake oil we finally settle with this Dixcel brake system. We have done alot of testing and we have collected all the data regard the brake disk/pad temperature, brake system surrounding temperature, life of brake disk/pad and We can see a real improvement by using high quality brake disk/pad.
 


Dixcelbrake

EK9.org Member
Joined
Apr 16, 2008
Messages
282
More info added -

In circuit driving, which Rotor is more beneficial: With slots Versus Without Slots or Heat versus non heat treated?

Firstly about slots, rotors with slot perform better than ones without. (According to the data from our tests, performance was improved by 15~20% by using slots. Also the gas discharge effect of the slot can lower the temperature of the whole brake system, which makes stable driving possible.

About running in of rotors
First, here is an instruction for street use only. It depends on combination of pads and conditions of road you drive on, it takes roughly 300km~1,000km of running-in on ordinary roads. During that time, please refrain from fast or abrupt driving or do not drive in a way as to force the temperature up. Running in of rotors will be completed simply via normal driving.

Circuit use

Distortion or cracks in rotors happen easier if optimum driving on a circuit is conducted straight from the beginning this in turn causes judders. When using a new rotor for the first time on a circuit, start with 50% braking for about 5 minutes and then go back to the pit once and take at least a 5 minutes interval. After that, repeat 70~80% braking for about 10 minutes. Pit in again and take an interval of about 10 minutes. After that, gradually increase from 80% to 100% braking and the running in of rotors on circuit is completed.
 


moon*

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what about in terms of cross drilled n slotted??

slotted would be a better choice?
 


RagingAngel

本田 Gearing Authority
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Mar 26, 2008
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Slotted rotors would be better. Dixcelbrake might be able to offer the technical data to support this but briefly put: Cross drilled rotors reduce the contact surface area. On a rotor that is already small, you want the most surface area as possible.

Cross drilled rotors crack for two main reasons. They are drilled into place instead of being cast. Secondly, the rotor gets overheated with the use of aggressive brake pads and repeated high speed stops. Think 300whp Civic with 9inch cross drilled rotors and an aggressive pad driven in a "spirited fashion."

I don't think cross drilled rotors are a good idea till 12inch diameters along with a sizable increase in width as well. Stock EK9 rotors are 22mm thick when new as a reference.

Dixcelbrake: What's your opinion and method on cooling ducts?
 


Dixcelbrake

EK9.org Member
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Apr 16, 2008
Messages
282
Drill disk is just for show use, they are useless on track. It will crack everytime you track it. Slotted disk is much stronger disk and will give you better stopping power as its stop building up air between the pad and disk. Also the slot will create a higher initital bite so you get better 'Feel' with the brake.

For the cooling hose, its not always necessary. You need to know what is the best working temperature with your disk and pad. Some pad gives the best performance at over 350+ degree so its depends what kind of track you are racing on and what brake setup you use.

With our Dixcel brake, we never suggest using cooling dust with our R01 pad or even normal Type Z pad. The R01 pad start working from 200+ degree and give the best performance from 250-800 degree. So unless you are doing some track like Rockingham, Cadwell park or something with loads of heavy braking corners with no long straight to cool down, there no need for braking dust at all.

Is fine to use the dust with our Type Z carbon pad, as this Z pad work from 0 degree to 850, so they will give you exact same performance at any temperature but keeping the pad cooler thats mean the pad won't wear out as quick. As when the Z pad get hotter they will become softer to help to mantain the brake performance.

With other non Carbon based brake pad which is 99% of other aftermarket on the market, its better to run brake cooling dust at all time. As normal pad are Steel based, Steel based pad store heat but Carbon don't store as much. When normal steel pad reach to 800 degree, the Type Z carbon pad will only get to 550 degree, R01 pad will be around 680.

We did a head to head testing with one another very popular brand on a brake dyno. The other brand reach to 1100 degree and our R01 pad only stays at 800 degree max and it won't go up any futher no matter what we done to it but its also mantain the exact same braking performance.

HTH

Dixon
 


rvm

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Nice info guys, thanks for sharing, I use slotted rotors in my car:

attachment.php


I think they're in good shape, right now I don't use the endless brake calipers, I use the oem ones :)
 

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moon*

New Member
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Mar 19, 2008
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247
hey guys. i m planning to change my brake pads.. my mech got a hold on this endless.. but i tried to find the code on the box or the brake pad. i cant seem to locate the model number other den this on the box.

any one got any ideas exactly which model is this n wat temp pad?

thanks.

dsc01365it7.jpg

dsc01364xf7.jpg
 



Michalion

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Jul 4, 2012
Messages
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It's so nice of you for sharing detailed information on the braking system. It's really helpful. Some of the things went off my mind because of complex words. Overall it is educative. Thanks a lot for sharing this info with us.:)
 


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