Many people ask frequently about braking systems, and what is better and exactly what is usable.
Everybody wants to go faster, handle better, braking is usually ignored, mainly do to the cost of major upgrades. After research and some experience most people will discover that, big brake kits, slotted, cross-drilled rotors have not crafted a huge dent in 60- or 70- stopping distances.
In this article we will look at what is important in stopping a vehicle and what factors are involved. Your reader should keep in mind concepts behind braking in this post. These concepts are universal, no matter what vehicle, we talk of, improving stopping distance is a matter of applying applications based on driving habits and driving conditions.
Read on and locate what you need to start stopping faster.
The following are terms you should have and know been supplied by brake system experts.
The clamping force of a caliper in pounds is the brake line pressure multiplied with the total piston area of the caliper in a fixed caliper as well as two times the complete piston area in a floating design. To boost the clamping force it is actually necessary to either increase the line pressure or even the piston area. Increasing the pad area or the coefficient of friction is not going to increase clamping force.
What does this mean? That your particular clamping force of your caliper and brake subsystems has nothing to do with pad design or makeup nor does it have anything concerning the type of disc used.
This next little bit of information is really the basis for stopping the vehicle. Improving this area will get your vehicle stopping faster
Coefficient of friction:
A dimensionless indication of your friction qualities of one material vs. another. A coefficient of 1. would be equivalent to 1g. The higher the coefficient, the higher the friction. Typical passenger car pad coefficients are in the neighborhood of .3 to .4. Racing pads are in the .5 to .6 range. With most pads the coefficient is temperature sensitive so claims that do not specify a temperature range should be viewed with some suspicion. The optimum is to pick a pad having a virtually constant but decreasing coefficient on the expected operating range of temperatures. As a result, the operator does not have to wait for the pad to heat up before it bites, and also the pad fade will not be an issue so that modulation will be easy
Now that we have a foundation we can observe that finding the pad of the right heat and material range affects your braking efficiency. Because you have to heat it up to the approriate heat range before it bites, you don’t want a pad race pad for the street. Not to far of from racing tires where their operating range is higher, so getting them to stick requires more heat.
The main difference is here you choose a pad for your car based on driving habits, much like you would tires.
If you are in the brakes non-generating and quit excessive numbers of heat then you want a rotor and pad combo designed to bite or grip at higher temps.
About the street we want bite straight away thus a pad having a lower operating temp, as well as the trade off is fade at higher temps, (excessive braking or high speed braking) or reduced bite.
Here is a run down of some common types of materials.
A braking system by which both pads and discs are produced from carbon composite material. Utilized in every method of racing where they are not outlawed, carbon/carbon brakes offer significant reduction in rotating mass and inertia as well as much greater thermal capacity and dimensional stability being used. The disadvantages include cost, a certain amount of lag time while heat builds up (especially in the wet) and some difficulty in modulation. In contrast to popular belief, the coefficient of friction is no better than that of cutting edge carbon metallic pads and cast iron discs. An important advantage on super speedways is the decrease in gyroscopic precession on corner entry.
It is a trademark in the Performance Friction Corporation. Pad friction compounds containing large percentages of pure carbon along with various metallic elements. Pioneered by Performance Friction Corporation these compounds offer very constant coefficients of friction vs. temperature characteristics along with increased thermal capacity. , since they both operate at higher temperatures and their temperature rises to operating temperature faster than other compounds, they increase thermal shock to the disc and increase thermal conduction to the caliper brake and pistons fluid,. That is the disadvantage. It is suggested to not use drilled discs with carbon metallic pads, as a result.
Thermal shock or disc being exposed to extreme temps causes a break in the bonds of the metals used in the discs which may cause cracking.
Is normal for brakes which can be exposed to hard braking, it is going to however result in shorter rotor lif, though thermal shock is different from bluing which is because of thermal stress on cast iron rotorse
Now through to Brake System Break in.
Bedding in: There are two types of “”bedding in”” pertaining to brakes:
Bedding of the friction material. All friction materials contain volatile elements used as binders. In the initial thermal cycling of the material these volatiles boil off, forming a gaseous layer between the friction material and the brake. A bedded pad will exhibit a layer of discolored material from 1.5 to 3 mm thick.
Bedding from the disc. Before using a new disk, all machining and preservative oils must be completely removed after the disc manufacturer’s recommendations. Usually it involves washing with soapy water or using among the proprietary “”brake clean”” compounds. The disc should then be checked and mounted for run out. It should be bedded in with numerous moderate stops with lots of cool off time between stops, gradually increasing the severity of the stops until the entire top of the disc is evenly discolored. This will prevent thermal distortion, shock and the formation of “”hot spots”” (regional deposition of pad material which results in a lasting transformation in the cast iron underneath the deposit) and ensure maximum disk life.
To properly burglary your pads and rotors we now know the importance of bedding in the materials.
When new pads are installed to bed them in run them through one complete heat cycle. This can vary in line with the type of pad and its heat range. Before subjecting them to race conditions, after one cycle has been completed allow them to fully cool.
It is advisable to bed new pads on bedded rotors, that are smooth and flat (Re-surfaced on a lathe) without any hot spots or bluing. When using new pads and rotors it needs a more delicate break in process. Heat cycling the pads once means more time for cooling the pad and rotor.
Here is a practical way to bed pads. (Assuming you just installed the new pads)
You should start by finding a safe location, uncrowded area preferably a track. Warm up the motor, and vehicle. Start with a series of low speed light braking manuvers to check brake system intgrity, post pad install. Inside a closed area or safe spot get started with harder stops from lower speeds 25-40 MPH. Slowly increase the speed and stopping power until they reach there specified heat range. This may be tough to tell, a genuine sport pad’s manufacturor will give you a heat range. After a series of 3-6 60-0MPH stops the pads should be cycled, you can always check the pad with a prod type thermometer or thermo pyrometer.
When the higher speed hard stops are applied if fade is evident begine the cool off process. Slow down, avoid using the brakes, and drive until you can park the automobile to allow the pads and rotors to attain atmospheric temperatures, before doing any racing or hard driving.
Following this procedure will maximize pad life, increase the co-efficient of friction bewteen the materials.
Since you now have that down lets reach the pedal effort you were discussing. This is called modulation. The stiffer and tighter the pedal may be the less force is transfered to the clamping system via the booster, and master cyl. The higher the pressure in the brake lines plus more pedal travel you have equals more force.
More pedal travel=Higher system pressure/clamping force harder to modulate
Stiffer pedal/tighter=Less pressure easier to modulate
The word given by this process by which the skilled driver controls the braking torque to maintain maximum retardation without locking wheels. Because the individual modulates most efficiently by force rather than displacement, effective brake modulation requires minimum pedal travel and maximum pedal firmness
The pads and rotors do not change this. They can increase your systems ability to increase hydrolic pressure though.
Mechanical pedal ratio:
The brake pedal is designed to multiply the driver’s effort. The mechanical pedal ratio is the distance from the pedal pivot denote the effective center of the footpad divided by the distance from the pivot point to the master cylinder push rod. Typical ratios range from 4: 1 to 9: 1.The larger the ratio, the greater the force multiplication (and also the longer the pedal travel)
This ratio can be adjusted by the installer.
So you can now see that brake modulation is essential for controlling your braking to maintain teh car stable, and has nothing to do with actual with
braking efficiency or braking tq.
There appears to be a misconception of what a ventilated disc is.
this can be a ventilated disc
This is a cross-drilled, slotted solid non-ventilated rotor.
This is a slotted ventilated disc
Many asked about the cross drilled rotors and how they guide cool the brake system. Well here is the short answer, air cools them, and without ducting running for your brake discs they are hardly more effective than your standard ventilated disc. The slotted rotors are for gassing, when the pads reach their operating temps or higher they start to gas or breakdown along with the slots exist to allow the gas to flee.
So, what cross drilled rotors do is reduce suface area decrease co-efficient of friction and they are more prone to thermal shock, and cracking unless, you have a specialized braking system using, special brake fluid, stainless steel brake lines, venting all the necessary items to aid in convection
One of only three heat transfer mechanisms. Conduction and radiation will be the other two. Convection will be the transfer of heat by fluid flow. Air can be considered to become fluid in a thermal style of a brake system when it is is and moving connection with the heated surfaces in the disc or drum. With regards to a solid disc the air moving over the top of the disc is extremely turbulent and random, but still functions to provide some cooling. In the case of a ventilated disc, by the pressure of a forced air duct or by induced flow that is caused by the centrifugal acceleration in the air already in the vent of a rotating disc, air flows throughout the vents. The atmosphere absorbs thermal energy down the vent path. In this way, the high temperature generated by the braking system of an automobile is transferred to the moving air stream and outside the brake disc.
The advent of carbon metallic friction materials with their increased temperatures and thermal shock characteristics ended the day from the drilled disc in professional racing, so far as cross drilled rotors go. They are still seen (mainly as cosmetic items) on motorbikes and several road going sports cars. Typically in original equipment road car applications these holes are cast then finished machined to provide the ideal conditions through which to resist cracking in use. But they will crack eventually under the circumstances described in another section. Properly designed, drilled discs tend to operate cooler than non-drilled ventilated discs the exact same design due the higher flow rates throughout the vents through the supplemental inlets and increased surface area inside the hole. That’sright and inlets, the flow is in the hole and out with the vent towards the OD from the disc. If discs are to be drilled, the external edges of the holes must be chamfered (or, better still, radiused) and should also be peened.
Thanks to By Stephen Ruiz, Engineering Manager and
Carroll Smith, Consulting Engineer at STOPTECH LLC for technical definitions.
It’s true, there are many pads available, for the tuner, knowing the a person’s driving style will help the average Joe make a educated choice when upgrading brake components.
And on the car, most people will be more interested in doing a kit with big calipers and rotors because of those reasons, “”Big Brake”” kits look great on paper. However, upgrading calipers and rotors does not mean that the car will stop faster. Chances are if the manufacturer has a brake system made with one piston calipers clamping 7″” disks, that probably means other brake system components won’t be taking full advantage of the. A tuner can’t always upgrade one system, if there is a weak link elsewhere. The systems need to be looked at as a complete. Most brake articles online talk about this, treating the brake systems as a whole. OEM makers don’t produce perfectly designed brake systems,. That is what they don’t mention typically. The pad and rotor combos utilized on most cars are to purchase them stopping fast and lasting long. Which brings this article to the main point: throwing on a sport pad is the easiest way to increase your COF, and will increase efficiency. Due to their lower operating temperatures if the tuner drives hard the OEM pads on most cars will gas. Sport pads will be better for individuals who like to stop fast at higher speeds or those who are on the brakes long amounts of time, without the need for big brake upgrades.
Increasing rotor size may also help, but, not without sport calipers. If both were adde the system might require true stainless-steel teflon brakelines, and a possible upgraded booster and master cyl. to accomodate the increased pressure needed to keep clamping force up, in addition to race/syn brake fluid.
People searching for a little more bite for hard braking might find using sport pads and slotted rotors for gasing a real treat. This combo is best realized for hard driving (IE: autox, roadrace). I suggest replacing or bleeding the brake fluid also to help pedal feel after an install of this nature.
In conclusion, I actually have found those who do brake upgrades are disappointed, by the longevity of them. Pads and rotors are a wear and tear item, in most cases performance brake parts last 1/2 as long as OEM solutions. Discovering how to break them in and the way they job is the driver’s key to stopping faster.