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cross drilled rotors

Best Brake Systems 301: Torque Friction Surface Area

By Richard FongBest Brake Systems 301: Torque Friction Surface Area stillen_u_banner_v1 (1)

Best Brake Systems 301: Torque Friction Surface Area Practice and experience lend to improving your driving skills. As you go faster and quicker, you will inevitably uncover more limitations of your vehicle’s hardware setup. In Brake Systems 101 and 201, we explored the basic bolt-on upgrades that help to improve initial bite, heat capacity and feel while retaining the stock calipers and rotor dimensions. However, even aftermarket upgrades have their limitations, especially when it comes to heat capacity, which leads to brake fade. This is where upgrading to a big brake kit could prove an effective solution.

Best Brake Systems 301: Torque Friction Surface Area radi-cal-full-kit-1

Understanding Big Brake Kits

As had been mentioned before, the factory equipment on most vehicles are selected as a compromise of cost versus performance – meaning that the vehicle manufacturer will offer you a safely adequate braking system necessary for your vehicle within their targeted budget. This opens the door to aftermarket improvements, and a big brake kit usually rides high on the list of upgrades. However, contrary to popular belief, upgrading to a big brake kit is not for the sole purpose of shortening stopping distances. Its greater merit is increasing the heat capacity of the braking system. Best Brake Systems 301: Torque Friction Surface Area increases the heat capacity of a braking system by incorporating larger rotors, larger pads and larger calipers. The increased surface area lends to greater heat capacity and an increased friction surface. (NOTE: Before investing in a big brake kit, consider the wheel size you are running, as some kits might require specific wheel sizing and offset to clear the rotor diameter and the larger brake calipers. Contact STILLEN for more information.)

Best Brake Systems 301: Torque Friction Surface Area AP7500

Physics of Braking

Braking is the conversion of kinetic energy (motion) into heat (and stopping power) by way of friction generated between the brake pads and the brake rotor surface. Put simply, the greater the friction produced, the greater the stopping power. However, with more friction comes more heat. While certain pad compounds thrive in specific operating temperature ranges, the collective brake system also has particular temperature requirements. Individual systems begin to fall short once their optimal temperature range has been exceeded. Increasing the temperature capacity by way of fluid upgrades and rotor cooling strategies are logical first steps. To take upgrades a step further, increasing the heat capacity by way of larger rotors and correspondingly larger calipers and pads add to the available rotor surface area and the size of the pads that can be used to generate friction.

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A Big Brake Kit not only benefits from increased friction surface area and greater heat capacity, it also benefits from a greater moment of torque.

Get More Torque From Your Brake System

Increasing the heat capacity and applying more friction are just two of the benefits that a big brake kit offers. Another important benefit comes in the form of increased torque. The application of torque is a matter of leverage. In the same way that increasing the amount of leverage by way of a breaker bar (torque arm) helps to increase the torque applied (moment of torque) to a bolt or nut, the same principle applies when increasing the rotor diameter and caliper size. Increasing the diameter of the rotor increases the torque arm and subsequently increases the moment of torque for braking. This is one of the significant advantages that a big brake kit has over a factory brake system.

Best Brake Systems 301: Torque Friction Surface Area GTR_Vane_CutawayWeb450

Rotor Designs

Most vehicles come equipped with vented rotors up front, which help to facilitate cooling of the rotors in order to mitigate the potential for brake fade. A variety of vent types (radial, pillar and directional) have been developed in the pursuit of efficient rotor cooling.

 

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The Disc Brakes Australia proprietary “Kangaroo Paw” pillar design (left) compared to a typical radial vent design (right).

Best Brake Systems 301: Torque Friction Surface Area DBA

As mentioned in Brake Systems 101, the various brake pad compounds deliver varying levels of endurance, initial bite and resistance to heat. Pads designed for the street require little warm up and offer great initial bite, but sacrifice braking performance (reduction in friction under conditions of excessive braking and heat build up) when subjected to an endurance or heavy use situation. By contrast, an endurance race pad can take a lot of heat while maintaining optimal friction, but they must be heated to racing temperatures before becoming effective, which is unlikely to be achieved during normal street driving. Somewhere in between, there are pads that offer a balance of performance and endurance that suit a wider variety of driving situations.

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Exotic Materials – STILLEN CCM-X Brake Upgrade

Technology and space-age materials have enhanced our world in many ways. When it comes to stopping, STILLEN and AP Racing have worked together to improve on the heavy yet nimble, Nissan R35 GT-R. Their efforts led to the development of the high thermal capacity (HTC) Carbon Ceramic Matrix brake rotor (CCM-X) that offers superior heat capacity compared to its iron counterpart. Once found only in the world’s most exotic sportscars, this is the first CCM rotor offering for a production tuner vehicle. In addition, STILLEN worked with Pagid to formulate its RSX1 pad material to offer easy bedding and greater performance for both street and track applications. During extreme performance testing at Auto Club Speedway, the HTC CCM-X rotors and RSX1 pads proved to run 142F cooler than previous generations of CCM rotors (1,346F vs. 1,488F), which validated the test results recorded on the brake dyno at AP Racing’s facilities in Coventry, England.

Best Brake Systems 301: Torque Friction Surface Area 3R1A9595 Zoomed 2

At the Limit

At this point the question is, how do you know when you’ve reached your brake system’s heat capacity? Since the friction between the pads and the rotor generates heat, this heat transfers into the components of the brake system (rotors, pads, calipers and brake fluid.)  If you’ve upgraded these basic brake system components with aftermarket components (as outlined in Brake Systems 101 and 201) and are still experiencing unresponsive braking and/or a spongy pedal feel after aggressive driving, you’ve likely reached the heat capacity of the brake system. This condition is referred to as brake fade.

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Don’t Get Faded

Brake fade occurs because the heat generated by the friction between the pads and the rotor has built up to the point that the pads are no longer able to create friction with the rotors (unresponsive braking) or pockets of air have formed in the brake lines due to brake fluid boiling (spongy pedal feel.) In both situations, heat is the culprit, which drives home the value of cooling the brake system. While adding brake ducts that direct air to the calipers and rotors certainly helps to facilitate cooling, increasing the amount of surface area available offers greater heat capacity and an increased friction surface area for use with larger brake pads and calipers.

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 More Surface Area

Generally speaking, improving a brake system’s heat capacity typically requires more iron and thus, larger rotors. Larger rotors offer more material to absorb and dissipate heat, as well as a larger friction area for a larger brake pad to be employed. This is also why larger calipers are an integral part of the big brake kit (to be covered in Brake Systems 401). By increasing the amount of friction surface, more heat can be stored before reaching temperatures that cause fade. The increased heat capacity also increases the usable range brake pads have that would not have been practical on a lower heat capacity setup.

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Mechanical Grip Improves Braking

While increasing the size of the brake calipers, pads and rotors inevitably improves the heat capacity and overall brake performance, a brake system is limited by another factor, mechanical grip. Mechanical grip refers to the tires, the only thing between your vehicle and the pavement, ground or terrain. In the case of road vehicles, the brake system’s ability to slow and stop a vehicle depends heavily on the tires. A vehicle with worn or inappropriate tires (i.e. endurance tires being used at a track day, rain tires when its dry, etc.) will not perform optimally compared to one fitted with tires suited to the purpose at hand.

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Continuing on the subject of big brake kits, the next issue of STILLEN University, Brake Systems 401, will go into caliper sizing and selection along with the mechanics of how they work. Do you need a 4-piston or 6-piston caliper? Is bigger always better? Check back with us soon!


Check out some of the available Best Brake Systems 301: Torque Friction Surface Area brake rotor and pad upgrades available at www.stillen.com!

STILLEN Sport Brake Rotors

Disc Brakes Australia

AP Racing By STILLEN

STILLEN Brake Pads

Hawk Performance Brake Pads

Ferodo Brake Pads

Mintex Brake Pads

Pagid Brake Pads


Got questions or ready to upgrade your brake system? Reach out to STILLEN :
866-250-5542
sales@stillen.com
Live Chat
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Best Brake Upgrades 101: Rotors & Pads

By Richard Fong

Best Brake System 101: Rotors Pads stillen_u_banner_v1

There’s no point in being able to go if you can’t stop. While an engine provides locomotion to a car, the braking system is what brings your vehicle to a stop. The average automotive brake system is hydraulic and typically consists of the pedal assembly, vacuum booster, master cylinder, hydraulic lines, calipers, rotors and pads – and of course, on nearly all modern vehicles, an Anti-Lock Brake System module and pressure tank.

STILLEN BRAKES 201 V2 CLEANED (11)

The braking system is not only a CRITICAL performance element, it’s also imperative for safety and the safe operation of a vehicle. That’s why STILLEN offers Brake Upgrades for a variety of vehicles, from big brake kits to performance replacement parts.

OE Replacement Brake Discs and Pads

As is often the case, many standard vehicle components are designed as a compromise – balancing quality versus price, versus Noise Vibration Harshness (NVH) concerns – the end result being a pad that isn’t well suited for trackday performance. This means that in all likelihood, your OEM brake pads probably don’t do very well in ‘high performance’ conditions.

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Brake Pad Construction

Brake pads are composed of a backing plate and a friction compound that creates friction when placed in contact with the brake rotors, enabling a vehicle to stop. The way your brakes work is kind of like how the brakes of a bicycle work. Pushing the pedal causes the calipers to squeeze the pads against the spinning wheel hub/rotor, slowing its rotation, much like your bike’s rubber brake pads grab the edge of the wheel of your bicycle to bring you to a stop.

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Before moving on, we need to remind you that a high performance pad is going to be noisier and dustier – those are the facts. If you’re wanting a pad that offers extreme performance without dust or noise, know that it just doesn’t exist, at any price. Sorry, but if you want performance from your brake system, you’re going to have to deal with brake dust.

Your Stock Brakes Probably Aren’t As Good As You Think

With the exception of premium performance-oriented vehicles that include performance brake components from the factory, most vehicles are equipped with braking systems that are best described as “Adequate”. If you take the average stock vehicle to the track or even on a spirited drive, and you’ll quickly learn its shortcomings. The sad thing is, many car’s brake systems can start to get overwhelmed after just a few aggressive corners.

Stillen Brake Pads Metal Matrix

 

What happens if my brakes can’t deal with the demands of performance driving?

To understand the importance of a good brake compound and just how big a role it plays, let’s do a quick thought exercise.

Imagine accelerating down a stretch of canyon road, you’re accelerating hard on the straights, and then braking just before engaging a turn, or series of switchback curves. The first time you hit the brake pedal, everything works as it should, shaving speed and allowing you to hit the apex of the turn with ease. However, a few corners (or hotlaps) later, suddenly, the pedal gets all mushy, and instead of slowing and allowing you to adjust your line, the car just plows ahead, because the brakes don’t have any bite. You desperately stomp on the brakes in hopes you can still adjust your speed, correct and make the turn– but your efforts are in vain. Before you realize it, you’re way past the apex and are either off line or off track, or even worse, into the guardrail or Armco barriers. This is the biggest problem of an insufficient brake system rearing its ugly head. This is the beast known as Brake Fade.

Brake Fade Graphic

What is Brake Fade, exactly?

Brake fade is the enemy of safe and reliable braking and it’s not your friend. Brake fade occurs when the friction efficiency and/or heat capacity of the brake pads or rotors is exceeded, and as a result, the ability of the brake system to slow or stop the vehicle becomes compromised. Whether it’s on a twisty mountain pass or on a racetrack, when you discover the limits of your vehicle’s braking performance firsthand, it leaves much to be desired in terms of performance. Fortunately, the aftermarket could be the answer to your problems, because chances are, someone offers a solution for your application. There are a few ways to mitigate brake fade.

Best Brake System 101: Rotors Pads HawkCleaned

Bring Back the Friction

One of the best performance mods for your car and most straight-forward upgrades you can make is a set of Brake Pads. Brake pads, like rotors and fluid, are wear items that can be replaced with upgraded versions of replacement parts. Most factory brake pads are designed to be as quiet as possible with as little dust as possible. These characteristics require compromises that take away from the performance of your brake pads.

Can You Put Race Pads On And Drive On The Street?

The demands of racing versus stop and go traffic are very different, OEM street pads don’t perform their best under race conditions, and outright RACE brake pads won’t perform well if used for street driving conditions. Logically, one might think, pads designed for “RACE” performance must be overkill for the needs of street driving, right? Frankly, no.

Way back in the good ol’ days of 2002, Popular Mechanics compared Jeff Gordon’s #24 NASCAR Monte Carlo against a fresh-off-the-line FWD Monte Carlo SS to get an idea how the race car performed relative to its streetcar namesake. One would think that the race car’s massive brakes would make it the obvious winner, right? Both cars were tested as is standard practice for a head-to-head – cold, like your car is when you first start driving after being parked for a while.  Can you guess what happened?
(ref: Popular Mechanics, November 2002, A Tale of Two Chevys)

Well, the street car Monte Carlo outperformed the #24 NASCAR racecar’s gargantuan race brakes and the street car stopped much shorter – the polar opposite of what ‘common sense’ would suggest. That generation of Monte Carlo wasn’t exactly a performer either, making its victory over the racecar that much more shocking.

Why? Because of the temperature the brakes were designed to work at. The NASCAR race car’s brakes are designed to be used HARD, over and over again when hot, braking from speeds well over 100… to get that kind of performance when the brakes are that hot, the engineers had to sacrifice performance when cold.

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This chart from HAWK Performance offers a great visual for the temperature ranges that brake pads are designed to operate in. As you can see, pads that perform well cold do not perform well past 700*f or so, and conversely, pads that perform well when hot don’t start to grab until 200-300* f.

The Right Pad for the Right Purpose

Each pad type and compound is optimized depending on your vehicle’s intended purpose. There are a plethora of High Performance OE Replacement Brake pads available from STILLEN, DBA Brakes and Hawk Performance to name a few, and these pads are offered in a variety of friction compounds ranging from organic and ceramic to semi-metallic to suit a variety of different driving demands.

The other thing to note here is that sometimes, a car is factory-equipped with high performance brake pads, but the generic replacement available from the local auto parts store might perform terribly by contrast. So, despite every part of the system working properly, underperforming brake pads mean it suddenly takes much more distance to stop than it used to- and if you’re used to the car’s original stopping distance, this increased in stopping distance could cause an accident, so be sure that the replacement pads you’re installing are able to handle the way you plan to use them, before you buy.
Pro-Tip: If the brake pad has “Quiet” in the name, it’s a safe bet that pad won’t do well on a track.

Let’s take a look at some of the pros and cons of different brake pad compounds so you can better determine what might be best for your needs.

Picking The Right Brake Pad Compound for the Way YOU Drive

Brake Pads Graphic

Organic (Common OEM Material)

Pros: Less aggressive rotor wear, decent initial bite, manageable brake dust generation

Cons: Mediocre braking performance, tends to wear quickly, prone to brake fade

Organic pads offer good initial bite (initiation of friction and slowing of the vehicle) and modulation for daily driven vehicles, but generally suffer rapid wear and fade when subjected to aggressive driving.

Best Brake System 101: Rotors Pads HawkFrontPads

Ceramic (Common OEM Material, Aftermarket Upgrade)

Pros: Moderate rotor wear, good wear characteristics, less prone to brake fade, moderate dust production, ideal for rotors lacking slots or cross drilling, the middle ground between organic and semi-metallic pads

Cons: Higher cost, limited compound options, less aggressive friction traits, not ideal for the track

Ceramic pads cost more but take the best traits of organic pads and can add longevity as well as reduced brake dust production. However, these pads suffer accelerated wear under heavy loads and are not ideal for track or heavy-duty braking situations.

Mintex Brake Pads NASCAR

Semi-metallic (Common Aftermarket Material, Aftermarket Upgrade)

Pros: Broad selection of available compounds, improved resistance to fade, improved heat rejection when used on slotted or cross-drilled rotors, permits tailoring of braking performance traits depending on driving conditions by changing compounds

Cons: Potentially aggressive rotor wear, excessive dust, noise (brake squeal)

Semi-metallic pads tend to resist fade better and offer superior heat capacity and dissipation compared to organic or ceramic pads. They are offered in a variety of compositions enabling the end user to choose the braking characteristics desired of their vehicle. When choosing a semi-metallic pad, aggressive initial bite could be desirable in the case of a vehicle driven hard for short intervals.

The counterpoint is that this pad could eventually suffer from fade with prolonged aggressive driving. By comparison, a semi-metallic pad formulated for endurance offers increased heat capacity for longer driving intervals, but will likely lack initial bite when cold and suffer reduced braking performance until brought up to optimal operating temperatures. This is not ideal for short driving intervals or street driving since the ideal temperatures are much higher and might not be reached under these conditions.

In other words, semi metallic endurance RACING brake pads will be unable to perform for “street use” because they will not be at their intended operating temperature a vast majority of the time – meaning it’s not smart to drive from your house to the race track on your ‘trackday’ brake pads. It won’t be fun when you roll right past that first stop sign or can’t slow down as you get off the freeway because the RACE COMPOUND brake pads are too cold.

As the only USA Distributor of AP Racing products, we’ve got a huge selection of replacement and performance replacement brake pads for a variety of applications here at STILLEN in stock and or readily available to suit your needs from the most trusted manufacturers in performance brakes. Whether it’s a daily driver or a track rat, we likely have a solution available – talk to our team today to see what we have for your application.

STILLEN J-Hook 2pc Rotors Set of 2

Release the Heat

Another common brake system improvement involves upgrading the surface that the brake pads apply friction to, the Brake Rotors. Brake rotors are not only a friction surface, they also serve another important function – they are also heat sinks. This means that they must draw away and dissipate the heat produced by the friction of the pads efficiently to stave off brake fade and ensure consistent braking performance. Factory brake rotors are typically made of iron, because it’s inexpensive and offers longevity and enough heat capacity for the average everyday driver. Trick is, the way the “average driver” drives a car is nothing like the ‘Spirited Drives’ you and I enjoy.

Not all iron is created equal, and STILLEN rotors are produced using an alloy that offers more efficient thermal transfer characteristics and features bigger, better flowing cooling vanes to create a rotor with superior cooling characteristics, but these added features and the use of more expensive materials does increase cost. As a result of cost-saving concerns, typical factory rotors do not benefit from the design elements and use less expensive alloys that lack the heat dissipation characteristics found in STILLEN brake rotors, making a set of Performance Replacement Brake Rotors an especially effective upgrade.

STILLEN J-Hook 2pc Rotors Detail pair

Fighting Fade With Improved Brake Rotors

Aftermarket brake rotors, like those offered by STILLEN, AP Racing and DBA (for example) feature a variety of benefits, thanks to engineering innovations like improved vane design (in the case of vented rotors) as well as cross drilling, slotting and other surface treatments. Many people mistakenly believe that rotors suck air in through the vanes, but it’s actually the opposite. Think about what happens when you have a dirt bike’s rear tire caked in mud, and then blip the throttle. The wheel spins, flinging mud OUTWARDS off the wheel and away. Same idea applies to how air flows through your rotor. Brake rotors draw in air from the center of the hub and the spinning of the rotor flings the hot brake gases outwards through the vanes, cooling the rotor.

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It works like this, when your brake rotor turns, it acts as an air pump, drawing in cooler air at the hub and forces that air out, carrying away hot brake gases out through the vents, so it’s worth saying that a rotor’s internal design can play a huge role in its effectiveness.

Best Brake System 101: Rotors Pads IMG_5988 Best Brake System 101: Rotors Pads IMG_5959

In the search for improved methods of heat dissipation, some manufacturers of vented rotors have implemented proprietary vane designs to facilitate improved airflow for better cooling of the rotors.

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As an added measure of cooling, some have turned to cross-drilling the rotor surface, which provides additional pathways for hot brake gases to escape, thereby enhancing cooling.

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Another brake rotor type is the slotted rotor. Most commonly, simple slots are cut into the rotor surface help to optimize the friction surface area while helping to release the gasses that build up between the friction material of the pad and the rotor surface. However, the downside of this rotor type is accelerated wear on the pads, meaning slotted rotors shorten the typical service life of the pads used with them.

STILLEN BRAKES 201 V2 CLEANED (8)

Some enthusiasts choose to go with both of these features and opt for Drilled & Slotted rotors, and still others go for the polar opposite and get “blank” rotors for an OEM appearance.

Step Up and Stop Better

Best Brake System 101: Rotors Pads IMG_8172

With a better grasp of the basics of brake upgrades and the first steps toward better braking for both performance and safety, contact us to order your upgrade today! Do you have more questions about what would be right for your application? Reach out to us at 866-250-5542, at sales@stillen.com or by live chat on our website stillen.com to help you select the product that best suits your needs.

In our next installment of STILLEN University, we’re going to explore brake system upgrades in greater detail and dig into Torque Friction Surface Area in Stillen U, Brakes 301! Check back with us soon!


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866-250-5542
sales@stillen.com
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So you’re thinking about upgrading your brake kit, but aren’t sure if you want to go with cross drilled slotted rotors vs J-hook rotors. First, both are great options and you will notice significant improvement in braking power over your factory discs. Now, it’s time to discuss the differences between the two brake disc options. See below for benefits of each option.

Cross Drilled Slotted Rotors

Cross drilled and slotted rotorsCross drilled slotted rotors are characterized by the lines or slots that are machined into the disc and span the face of it. They also feature holes that have a chamfered edge that are drilled into the rotor and must align with the internal vanes of the rotor.

Aids in Cooling– The cross drilled design that works with vanes of the rotor to help keep your brakes cool, which allows you to push your car harder and still know that you will be able to stop without a problem.

Provides Extra Bite– Cross drilled slotted rotors improve initial pad bite with the leading edge of the hole and slot. This allows the pad to really grab a hold of the rotor and bring you to a stop faster.

Fresh Pad Surface & Optimum Performance– Get the most out of your high performance brakes with cross drilled slotted rotors. The design of the rotor allows it to evenly go over the pad and also allows for outgassing to keep the pad fresh.

J-Hook Brake Rotors

J-hook rotorJ-Hook rotors prominently feature a hooked pattern that is machined into the face of the rotor. This pattern has previously been utilized on the track and has just recently become available for general use.

Increased Durability– During the machining process, J-Hook rotors are not penetrated through the rotor. This makes the rotor more durable and helps prevent surface cracks. What this means for you is the rotors can be driven harder and at higher temperatures than other comparable rotors.

Additional Bite– If you’re looking for extra bite, the j-hook rotors are the brake discs for you. Like cross drilled rotors, they provide a great initial bite on the pad and extra grip, but they take it a step further. The J-hook design provides leading edges for the brake pad that create additional bite you are looking for.

Cleaning & Outgassing– Like the cross-drilled rotor, the J-hook rotor cleans the pad surface and allows for outgassing through it slotting of the rotor face.

More Information About Cross Drilled & Slotted vs J-Hook Rotors

Learn more about the differences between cross drilled slotted vs J-hook rotors at apradical.stillen.com. We feature a full J-hook rotor page and a full cross drilled/slotted rotor page that allows you to get more detailed information about each option. We also feature a full team of specialists that are happy to answer any questions that you have. Just give us a call at 866-250-5542 and we will be happy to help you!