Frequently Asked Questions
Carbotech Compounds and Applications
Friction materials have evolved significantly over the years. Brake pads were originally made with organic ingredients such as asbestos and carbon, held together by a strong resin. Asbestos brake linings were used because it was heat-resistant to the intense friction and heat produced in braking. They've gone from asbestos to organic to semi-metallic formulations. Each of these materials has proven to have advantages and disadvantages. Some of those advantages and disadvantages are noise, wear, stopping capability and environmental friendliness. The use of asbestos was eventually banned by the
Asbestos pads caused health issues and organic compounds can't always meet a wide range of braking requirements, such as high performance driving. Unfortunately the steel strands used in semi-metallic pads to provide strength and conduct heat away from rotors also generate noise and tend to cut up rotors as well. At Carbotech, we felt this kind of friction materials were not the best solution, and we decided to develop something that was better in performance and better for the entire braking system. That’s when Carbotech decided 14 years ago to take a path not taken by any other brake pad manufacturer.
Friction materials that contain ceramic formulations have become recognized for their desirable blend of traits. Ceramic compounds use copper fibers (amongst other materials) in place of the semi-metallic pad's steel fibers. This allows the ceramic pads to handle higher brake temperatures with less heat fade, and provide faster recovery after the heavy braking.
Another characteristic that makes Carbotech-Ceramic™ materials attractive is the absence of noticeable dust. All brake pads produce dust as they wear. Carbotech-Ceramic™ compound ingredients produce a light colored dust that is much less noticeable and less likely to stick to the wheels. On that same note, all Carbotech compounds produce a 100% non-corrosive dust that can usually be rinsed off with a hose.
Ceramic compounds extend brake life compared to most other semi-metallic and organic materials, and at the same time they outlast other premium pad materials by a significant margin, without compromising in noise control, pad life, and all around braking performance.
Most brake pads sold today are considered semi-metallic, semi-metallic brake pads use brass, copper, and steel wool shavings held together by a resin. Unfortunately the main drawback about the use of steel strands, iron, graphite, and small amounts of filer and friction modifiers (used to provide strength and conduct heat away from the rotors) is that the metal shavings and iron must rub against steel rotors every time the brakes are applied. This can also generates a lot more noise and are a lot more abrasive on the rotors. It also creates corrosive dust that can damage your braking system as well as the paint on your wheels and car.Back to Top
The Carbotech 1521 is our high performance street compound. The 1521 compound is known for its release and modulation, along with unmatched rotor friendliness. 1521 is also a very low dusting and low noise compound with an excellent initial bite. This compound's excellent linear torque production provides incredible braking force without ABS intervention. Carbotech 1521 operating range starts out at ambient and goes up to 800°F (426°C+). 1521 is suitable for ALL street cars, perfect for your tow vehicle or fleet vehicle. Carbotech 1521 is NOT recommended for ANY track use.
The AX6 is specifically engineered for Autocross applications. A high torque brake compound delivering reliable and consistent performance over a very wide operating temperature range of 50°F to 1000°F + (10°C to 537°C+). The advanced compound matrix provides an excellent initial bite, high coefficient of friction at lower temperatures along with very progressive brake modulation and release characteristics. Many drivers use the AX6 for street driving as well, even though Carbotech doesn't recommend street driving with AX6 due to possible elevated levels of dust and noise. AX6 is NOT recommended as a race compound in most applications.
A high torque brake compound with a wide operating temperature range of 200°F-1250°F+ (93°C to 676°C+). Carbotech XP8 is the first of our racing compounds. Good initial bite at race temperatures, high coefficient of friction, excellent modulation and release characteristics. Extremely high fade resistance and very rotor friendly. Perfect for track day use with any tire and can still be driven safely to and from the track. Carbotech does NOT recommended XP8 as a daily driven street pad due to elevated levels of dust and noise. Carbotech XP8 is a great compound on the front & rear of most open wheel and sports racers.
When Carbotech unleashed the XP10 to the general public it immediately gathered multiple regional, divisional, and national championships. The XP10 has a very strong initial bite with a coefficient of friction and rotor friendliness unmatched in the industry. Fade resistance is in excess of 1475°F (801°C). XP10 still maintains the highly praised release, excellent modulation and rotor friendliness that have made all Carbotech compounds so successful. Carbotech XP10 is not recommended as a daily-driven street pad due to possible elevated levels of dust and noise.
Another highly successful XP series compound with an excellent initial bite, torque and fade resistance over and above the XP10 compound. XP12 has temperature range of 250°F to 1850°F+ (121°C to 1010°C+). The XP12 has that excellent Carbotech release and modulation that has made all other Carbotech compounds so successful. The XP12 is more rotor aggressive than XP10, but compared to the competition the XP12 is still very rotor friendly. XP12 is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise.
The latest iteration of the highly successful XP series of compounds. XP20 is a step up from the highly successful XP16 compound. With an extremely aggressive initial bite, linear torque curve and excellent fade resistance the XP20 is another major step in progression of the highly successful XP series line of compounds from Carbotech. XP20 has a temperature range of 275°F to 2000°F+ (135°C to 1093°C+). Carbotech XP20 maintains our tradition of having the outstanding release and modulation that has made all other Carbotech compounds so successful. Carbotech XP20 is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise.
XP24 is the pinnacle compound of the extremely successful XP Series of compounds engineered by Carbotech. This compound is based on the same fundamentals that exist in all other Carbotech formulations. XP24 has even more initial bite, more overall bite, and more torque along with the most linear torque curve we have ever offered. The thermal characteristics are of the highest Carbotech offers along with one of the highest coefficient of friction ratings offered by anyone in the braking industry. This compound is the longest wearing compound Carbotech offers as it was originally engineered for endurance applications at the highest pro racing levels. This revolutionary new compound has been extremely successful with open wheel, closed wheel, sprint and endurance applications. XP24 has a temperature range of 400°F to 2000°F+ (204°C to 1093°C+). Carbotech XP24 is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise along with the necessary heat required to work properly.
The RP2 compound was engineered for endurance racing based on our highly successful XP Series formulations. RP2 has strong initial bite, a little less modulation than our XP12, but still maintains the rotor friendliness of our XP series compounds. RP2 has great fade resistance with a temperature range of 250°F to 1450°F+ (121°C to 787°C). RP2 is as rotor friendly as our XP series compounds. Carbotech RP2 is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise.
Carbotech 913 Kelated Metallic
A D.O.T.-approved high-performance compound for brake shoes on high performance street vehicles and race cars. Carbotech Kelated Metallic (CKM) achieves a very high coefficient of friction (approx. 0.48 to 0.50) by taking advantage of a chemical reaction within the friction mass, which creates a tri-alloy metallic film at the liner/drum interface when subjected to heat and pressure. Designed to overcome the shortcomings of other liner materials, CKM is a very versatile and provides excellent braking performance in a wide variety of applications. Excellent wear characteristics and a very high resistance to lock-up under hard braking. Optimal recommended operating temperature range is from ambient to 750°F.
There is no one answer for every person and/or every car. One drivers driving style and their vehicle might find the performance of our XP10 the best. Another driver with the exact same car might find the XP12 to suit them the best. A third driver with the same car, but different tires might find the XP8 compound to work best for their car, driving style, and tires. So, we can help you narrow it down to one or two compounds based on what you tell us; then we can give you the different characteristics of the two and let you decide (we will give our opinion on which compound we think will suit your needs the best). You might know just based off what you read on our site. Read the entire compound description section first, then if you still don’t know or have any questions at all please give us a call or send us an email. At Carbotech all of our customer service specialists are also racers and track day enthusiasts that have the technical knowledge and on-track experience to assist you in every way.
High performance street/track brake pads are a special breed of brake pad. Each brake pad has to be engineered to withstand the rigors of frequent and extremely hard braking. High performance brake pads have be able to withstand the extreme heat that can build up on the street and track.
YES, ABSOLUTELY. There isn’t anything Carbotech can’t make when it comes to your brake pads or your brake shoes. If we don’t have your pads/shoes or if we can’t get your pads/shoes (which isn’t often) just send us your cores and we can clean them up and reline them with any of our brake compounds. It’s that easy. The only thing you can’t send us is old pads and shoes that are lined with asbestos. You need to clean off the asbestos yourself and then send us the backing plates or shoe frames. If you can’t get the asbestos off then just give us a call and we will help you arrange something.
There is no specific mileage interval at which the brakes need to be relined because brake wear varies depending on how the vehicle is driven, the braking habits of the driver, the weight of the vehicle, the design of the brake system and a dozen other variables.
Bedding Procedure and Proper Maintenance
1. Why should I follow bed-in procedure?
Proper bedding of pads & rotors will result in greater performance and longer pad life & less rotor wear. Failure to properly bed in your pads could lead to friction materials chunking and breaking up. This could also lead to overheating your pads and causing them to glaze over resulting in the car not being able to stop or slow fast enough.
2. Do I have to resurface (turn) the rotors, or get new rotors?
If you have had another manufacturers brake pads on those same rotors; then you will ABSOLUTELY have to replace or resurface (turn) those rotors before installing the Carbotech brake pads.
If the rotors and drums are in relatively good condition, meaning they are smooth, flat, with no visible cracks, deep scoring, distorted, and with no other visible damage; and you have ONLY had Carbotech brake pads on them, then they do not have to be resurfaced or replaced.
3. Do rotors require a bedding process?
New rotors just like new pads need to be bedded in. Brake rotors don’t require as much bedding as brake pads require. If you follow the brake pad bed-in procedure your rotors will be completely bedded. Proper bedding will increase the rotor life and make it more resistant to thermal cracking. By cleaning the disc surface you want to make sure you have completely removed any and all grease, surface residue, and debris that might contaminate or damage the brake pads.
4. What’s the proper way to bed pads & shoes?
Proper bedding instructions for AX-Series & XP-Series Compounds :
- All new brake pads require a bedding process, start this process by pumping your brakes a few times to assure proper installation. Once on track perform several moderate (medium) near stops (to a very slow rolling speed) to thoroughly warm up the pads and rotors. This should take 1-2 laps. This allows a thin layer of the pad material to be transferred into the micro-grooves of the rotor.
- After the pads/rotors are warm, perform a series of hard near stops (to a slow rolling speed) until some brake fade is felt. This process should take about 2-4 laps (depending on the track). Once this occurs, then stay off the brakes (as much as possible) and bring your car into the pits/paddock to completely cool. Do not lock the tires during this operation.
- Allow brake pads and/or rotors cool down to ambient temperatures; no less than 30 minutes. The total bedding procedure should not take more than 5-6 laps or about 10-15 minutes.
NOTE: The proper way to bed your brake pads and brake discs (rotors) is to bed them on the racetrack, NOT on the street (excluding the Bobcat 1521 compound).
Warning: Failure to properly bed in your pads could lead to friction material to chunk and break up resulting in poor pad performance and pad life. Improper bedding can also lead to overheating your pads and causing them to glaze over resulting in the car not being able to stop or slow properly.
5. What is the proper way to bed brake rotors?
New discs (rotors) just like pads need to be bedded in. Proper bedding will increase the rotor life and make it more resistant to thermal cracking. Before installing the new brake discs (rotors), be sure to thoroughly clean discs with clean wipes and brake cleaner. By cleaning the disc surface you want to make sure you have completely removed any and all grease, surface residue, and debris that might contaminate or damage the brake pads. Once the discs (rotors) are installed on the vehicle perform the following procedure. Please note that you can bed new pads & discs (rotors) at the same time.
- Start out with several near stops for the first 1-2 laps, while gradually increasing your speed and brake force with every stop.
- Next, do another 1-2 laps at normal speed followed by a cool down lap. The gray coloration is the pad material depositing a transfer layer of material into the micro-grooves of the disc. This process is pinnacle in achieving the best performance and life out of the rotor.
- Then allow rotor(s) to completely cool down to ambient temperature.
Proper USED brake rotor bed in procedures:
- If rotors have been previously bedded with Carbotech brake pads, then bedding the rotors again is not necessary.
- If rotors were previously bedded using a different manufacturer’s brake pads; then it is strongly recommended that the used discs (rotors) be reconditioned/turned and meet minimum specification requirements.
- Start out with several near stops for the first 1-2 laps, while gradually increasing your speed and brake force with every stop.
- Next, do another 1-2 laps at normal speed followed by a cool down lap. The gray coloration is the pad material depositing a transfer layer of material into the micro-grooves of the rotor. This process is pinnacle in achieving the best performance and life out of the rotor.
- Then allow rotor(s) to completely cool down to ambient temperature.
NOTE: Brake pads should be checked regularly. If pads are wearing evenly, then the pads can be used almost down to the backing plate.
NOTE: Do not drag your brakes; meaning, do not continually drive around the track with applied pressure to your brake pedal. This does not bed brake pads and/or rotors properly. This can severely hurt the performance and life of your brake pads & rotors.
6. Should I clean rotors/drums and/or pads/shoes before installing them?
Before installing new brake rotors (always install rotors in axle sets), be sure to thoroughly clean the rotors with clean wipes and brake cleaner. Make sure you completely remove any grease, surface residue, and debris that might contaminate or damage the brake pads.
Reconditioning (turning) rotors/drums can leave a lot of metallic debris on the surface which can embed itself into the new brake pads or brake shoes and cause noise and many other problems. Even if the rotors or drums have not been resurfaced, cleaning is strongly recommended to remove dirt and grease. Dirt and grease can contaminate brake pad & brake shoe compounds and cause uneven braking or grabbing.
7. What’s the proper maintenance with a disc brake system?
- Flush all old brake fluid out of your vehicles system.
- Refill your brake system with new (fresh) better performing brake fluid
- Check for leaks by closely examining the entire brake system.
- Check fluid level and for fluid leaks on a regular basis.
- Bleed each caliper on a regular basis.
- Check pad thickness on a regular basis.
- Replace any pads that are worn down below recommended thickness.
- Check for debris or buildup of any kind in the caliper that could prevent the pads from extending and/or retracting properly.
- Also check for any burrs or dings on the exposed area of piston to prevent damage of any internal seals during piston retraction.
- Make sure all brake hoses are connected properly to the caliper and are tight enough to prevent separation from the caliper.
- Check to make sure all bolts and screws are torqued (tight) properly.
- Regularly check condition of rotor (cracks, deep scoring, odd markings, etc…).
- Make sure rotor is securely attached to the hub, and that the hub is securely attached to the vehicle.
- Make sure all wheels rotate freely.
- Blow away the brake dust with an air hose from time to time.
Troubleshooting Brake Procedures
1. What causes brakes to drag?
- Warped rotors.
- Bad master cylinder.
- Residual pressure valve in system.
- Calipers are not square to rotors.
- Tapered brake pads.
- Debris in the caliper that’s not allowing the brake pads to retract properly.
2. What causes brakes to make noise (squeal)?
Lack of friction material on the backing plate is the most common result of brake noise. Another reason for brake noise is that the pads are loosely fitted into the caliper. Debris caught between the brake pad and rotor is another of the common reason’s for brake noise. Loose lug nuts or caliper hardware. Cracked or worn rotors. Uneven finish on reconditioned (turned) rotors.
Loose or missing brake hardware (anit-rattle clips, shims) can be responsible for brake noise. There are steel springs and pins which allow the pads mounted in the brake calipers to move freely without rattling and vibrating excessively. However, due to the nature of your brake system, these pins and springs wear and loosen their tension over time. Worn pins can result in binding, squealing, brake fade, uneven braking and reduced pad life.
Sometimes brake noise on certain vehicles is completely normal and no maintenance is required. Brake noise can be caused by the everyday vibrations of daily driving on the brake pads, rotors, and calipers; whick is also known as Noise, Vibration and Harshness (NVH) a common term in the automotive industry.
3. Why am I getting oscillating feed back?
Cracked rotors, rotor faces not parallel, or there is pad material build-up on the rotor surface. Excessive rotor run out is another reason for oscillating feed back.
4. What causes rotors to warp?
Warping can be caused by not properly torquing the lug nut(s). Over-torqued or unevenly torqued lug nut(s) with an impact wrench is a common cause and not recommended. A vehicle manual will indicate the proper torque rating and pattern for tightening lug nuts. Lug nuts should never be tightened in a circle, most use the diagonal method, but again check your manual. Vehicles are sensitive to the amount of torque the bolts apply and tightening should be done with a torque wrench. A plain impact wrench should never be used for the tightening of the lug nuts because most provide no control whatsoever over the amount of torque applied to the nuts. . There are also special torque-limiting extension sockets called "Torque Sticks" that can be safely used with an impact wrench to accurately tighten lug nuts.
Another primary cause of warping is caused by excessive heat, which can soften the metal and allow it to be reshaped. Warping can also be caused by the disc being slightly overheated and the vehicle is stopped and keeping the brakes applied. When you keep the brakes applied the very hot pads contact the slightly overheated disc will cause uneven cooling and eventually lead to warping.
Riding the brakes lightly will generate a great amount of heat and is not the proper way to brake with a vehicle. The proper way is to apply the brakes strongly for a shorter distance and then completely release the brakes. This will allow the brakes to cool before the next application, and by riding them lightly for a greater distance constatly builds heat and over the pads and rotors. Racing brake pads have the ability to handle this because they are engineered to properly handle extremely high temperatures. High performance brake pads for the race track can take very high heat, but most do when hot and won’t brake as well when cold. One of the beautiful things about Carbotech-Ceramic pads is their effectiveness when cold.
Warping will often lead to a thickness variation of the disc. If it has runout, a thin spot will develop by the repetitive contact of the pad against the high spot as the disc turns. When the thin section of the disc passes under the pads, the pads move together and the brake pedal will drop slightly. When the thicker section of the disc passes between the pads, the pads will move apart and the brake pedal will raise slightly, this is pedal pulsation. The thickness variation can be felt by the driver when it is approximately 0.007 inch (0.017 cm) or greater.
Not all pedal pulsation is due to warped discs. Brake pad material operating outside of its designed temperature range can leave a thicker than normal deposit in one area of the disc surface, creating a "sticky" spot that will grab with every revolution of the disc. Grease or other foreign materials can create a slippery spot on the disc, also creating pulsation.
5. Why do brake rotors crack?
Cracking is limited mostly to drilled discs, which get small cracks around outside edges of the drilled holes near the edge of the disc due to the rotor's uneven rate of expansion in severe duty environments. Manufacturers that use drilled rotors as OEM are doing so for two reasons: looks, if they determine that the average owner of the vehicle model will not overly stress them; or as a function of reducing the unsprung weight of the brake assembly, with the engineering assumed that enough brake rotor mass remains to absorb racing temperatures and stresses. A brake disc is a heat sink, so removing mass increases the heat stress it will have to contend with. Generally an OEM application that is not drilled will crack and could fail catastrophically if used over and above the original equipment design. Once cracked, these discs cannot be repaired. Carbotech does not recommend cross drilled rotors for any kind of track use.
6. What is brake fade?
Fade, or brake fade is the reduction in stopping power caused by a buildup of heat in the braking surfaces (and in the case of drum brakes the arc of the brake shoe don’t match the arc of the drum in response to heat). Brake fade can also be caused by the brake fluid boiling. Compounds are held together by resins, these resins can revert to gas when high temperatures are reached. When this happens the brake pads can “aquaplane” on a film of gas created by the over heated resins. Many low quality pads suffer continuous fade at very low temperatures.
7. What causes a spongy pedal?
A spongy pedal almost always is a result of air in the brake system. Other reasons could be, wrong size master cylinder (too small), calipers not mounted square to the rotor or are mounted equal to or higher than the master cylinder. Another reason could be a result of the pedal ratio being too great.
8. Why did I lose my brake pedal during the race?
In most cases this is a result of the brake fluid boiling. Another of the usual suspects are faulty master cylinder or a leak in either the caliper or brake lines. Sometimes this could be the result of an undersized brake system.
9. Why do I have to push really hard on my brake pedal?
The brake pads and/or rotors were not properly bed. Glazed brake pads and/or glazed rotors. You may have chosen the wrong brake pad compound for your application. The master cylinder could be too large, or an insufficient pedal ratio
10. Pedal is low when I first step on it, if I pump it the brake pedal comes up, why?
A low brake pedal that has to be pumped repeatedly to bring a vehicle to a stop may be due to a low fluid level, drum brakes that need adjustment or air in the lines.
11. My brake pedal slowly sinks to the floor, why?
You most likely have a fluid leak in your brake system. This can be checked by looking at your fluid level in your reservoir. If one of your two chambers are low (one chamber for each brake circuit, usually one for front and one for rear) then you definetly have a leak somewhere. The other option (if you don’t have a leak) is that you have a bad master cylinder.
1. Why do I need to bleed my brakes?
To remove moisture that entered the system. Brake fluid needs to be replaced periodically, because brake fluid will absorb moisture over time. This occurs whether a vehicle has been driven 60,000 miles, or has been sitting in a garage for a year. Fluid contamination is a function of time and humidity, and has nothing to do with the mileage driven. Moisture enters the brake system through seals and through microscopic pores in the hoses. Moisture enters the system every time the fluid reservoir is opened, which is a good reason not to open it unnecessarily.
To remove air bubbles that have entered the system because of a leak or because the fluid level got too low. The air must be removed because it is compressible and will result in a soft, “spongy” brake pedal.
2. How do I bleed my brakes?
Bleeding Process: It takes two people
- First, always start at the corner furthest from the driver and work your way towards the driver/master cylinder (Right rear, left rear, right front, left front.), just remember farthest to closest.
- Then, find the bleeder screw (bleeder valve) on the rear caliper. Attach a piece of clear tubing to the nipple of the bleeder screw.
- Place the other end of the hose into the disposable bottle.
- Then take a wrench and place it on the bleeder screw.
- Place the bottle for waste fluid on top of the caliper. Hold the bottle with one hand and grasp the wrench with the other hand.
- Next, have your assistant apply the brake pedal and hold down firmly. Then open the bleed screw ¼ turn to release the fluid into the waste line. NEVER have the driver release the brake pedal while the screw is open, make sure to CLOSE the screw first and then have the driver release the brake pedal.
- Inspect the fluid within the waste line for air bubbles.
- Continue the bleeding process (steps 1 through 7) until air bubbles are no longer present. Be sure to check the brake fluid level in the reservoir after bleeding each wheel, make sure to keep the fluid level at the MAX line.
- Then, go on to the next corner and repeat all steps (1-8).
- Next, take brake clean and spray and whipe down the entire area until dry. DO NOT SPRAY BRAKE CLEANER ON ANY RUBBER OR PLASTIC PARTS. Leaving the area clean and dry will make it much easier to spot leaks.
- Test the brake pedal for a firm feel, and if all the steps were followed then your done bleeding your brakes.
- Please discard of any and all used brake fluid properly and responsibly.
3. Basic brake fluid & fluid maintenance information.
Brake fluid is hygroscopic, meaning it absorbs water. When new from the bottle, it can be considered "dry" with a higher boiling point. Over time, brake fluid absorbs water lowering its boiling point to the "wet" level. Changing brake fluid removes water from the brake system and is extremely important. Change your brake fluid at least every two years … much more often for cars that see track use.For street cars, wet boiling point numbers are more important than dry because the fluid stays in your car for a long time (change it at least every two years). After months of exposure to humid air and changing climate conditions, brake fluid performance is closer to the wet boiling point than the dry boiling point. When brake fluid boils, it turns into vapor and forms air bubbles. This creates a “soft pedal” and requires excessive pedal travel to apply the brakes properly. Do not confuse this with "brake fade". Brake fade occurs when the brake compound gets too hot from prolonged braking or improper bedding. Brake fade requires greater and greater pedal effort to stop the vehicle; boiling fluid increases pedal travel and makes the pedal feel soft.Due to the extreme temperatures that high performance brake systems operate at, standard brake fluids are not recommended for track use.Carbotech™ Performance Brakes does not sell and does not recommend silicone based brake fluid with any of its products. For more information, please scroll down to “A Word of Caution”.
4. A word of caution about brake fluid!
A Word of Caution …
Neither Carbotech Performance Brakes nor AP Racing markets silicone brake fluids nor recommends their use with any braking system.
Virtually all of the problems with silicone brake fluids reflect certain properties of silicone fluids identified by us over many years and recently ratified in SAE publications, specifically: high ambient viscosity; high air absorption; high compressibility; low lubricity; and immiscibility with water. Research has shown that these properties of silicone fluid result three performance problems:
Long Pedal Travel or “Spongy” Pedal caused by:
- High compressibility, up to three times that of glycol based fluids;
- High viscosity, twice that of glycol based fluids, leading to slow rates of fill and retention of free air entrapped during filling, and hence bleeding difficulties.
A Sudden Loss of Braking resulting from:
- Air absorption - gasification of absorbed air at relatively low temperature produces vapor lock effect;
- Immiscibility (failure to mix) with water - whilst the presence of dissolved water will reduce the boiling point of glycol based fluids, any free water in silicone-filled systems will boil and produce vapor lock at much lower temperatures (100°C or thereabouts)
“Hanging On” of brakes due to:
- Low lubricity - in disc brake systems the sole mechanism for normalization of system pressure upon release of pedal pressure is a designed-in tendency of seals to recover to their ‘at rest’ attitude. Low lubricity works against this tendency.
- High viscosity exacerbates the effects of low lubricity.
The high price of silicone fluids does not produce higher performance in hard driving or even normal road use.
AP Racing glycol based fluids do not exhibit the adverse properties of silicone fluids. The recently introduced Formula DOT 5.1, which exceeds the performance criteria of DOT 5 (Silicone), is suitable for all conditions likely to be encountered in modern driving conditions.
5. Can brake fluid damage brake pads?
ABSOLUTELY, that’s why it is so vital that the hydraulic system is in good working order with no leaks. This doesn’t mean that you have to throw away your brake pads. Clean them compounds off and take them to a grinder (if needed) to grind off the contaminated compound material. Please consult a professional before using a grinder, and to make sure the pads are safe to use again.
6. What is a master cylinder?
The master cylinder is a control device that converts physical pressure typically from a driver's foot applying pressure on the brake pedal, into hydraulic pressure to operate other devices in the hydraulic system. In brake systems, the operated devices are brake calipers.The master cylinder displaces hydraulic pressure to the rest of the brake system.
There are two separate systems that may be supplied by separate fluid reservoirs, or they may be supplied by the same reservoir. Most brake subsystems are divided front to rear. Some can be diagonally separated.
7. What is a slave cylinder?
Slave cylinders (also known as wheel cylinders), are cylinders where movable pistons convert hydraulic brake fluid pressure into mechanical force. Hydraulic pressure against the pistons within the wheel cylinder forces the brake pads against the surface of the rotor. There is one cylinder (usually) for each individual wheel, which is built into the calipers.
8. What is a brake booster?
The modern brake booster is a brilliant device that operates using engine vacuum, engine vacuum is generated whenever the engines running. The brake booster takes engine vacuum via a rubber hose that runs from the intake manifold. The brake booster uses that vacuum to amplify the pressure you put on the pedal ensuring that your car stops more rapidly. What happens to the brake booster if your car stalls and loses it’s vacuum? Engineers realized early on that gas engines were not foolproof, so they engineered a check valve within the brake booster circuit. The brake booster stores enough vacuum to provide full boost for two or three pedal applications after the engine stalls. The check valve on the brake booster is what keeps that vacuum from leaking out. If the brake booster can’t hold vacuum its time is up and you’ll need a new or remanufactured brake booster.
Brake System Descriptions
1. What is a basic description of a brake system?
A brake is a device for slowing or stopping the motion of a machine or vehicle. The brake system is composed of the following basic components: The master cylinder which is located under the hood, and is directly connected to the brake pedal, converts your foot's mechanical pressure into hydraulic pressure. Brake lines and flexible brake hoses connect the master cylinder to the slave cylinders located at each wheel. Brake fluid fills the brake lines, hoses, calipers, and resevior. Shoes and brake pads are pushed by the slave cylinders to contact the drums and rotors thus causing friction which slows the car down.
2. What is a brake caliper?
The brake caliper is a U-shaped device with a piston or pistons on one or both sides of the U. The brake pads sit infront of the piston(s) on each side of the U-shaped caliper. When the brakes are applied, high-pressure fluid is channeled from the master cylinder to the brake caliper where it pushes the piston(s) inward. This action moves the pads against the spinning brake rotor, and the friction stops your vehicle. There are two types of calipers, a floating or a fixed caliper. A fixed caliper does not move relative to the disc. It uses two or more pistons to clamp from each side of the disc, and is more complex and expensive than a floating caliper. A floating caliper moves with respect to the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the brake rotor surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc.
3. Brake drums vs. brake discs?
4. What is the primary function of a brake pad?
A brake is a device for slowing or stopping the motion of a machine or vehicle, and to keep it from starting to move again. The kinetic energy lost by the moving part is usually translated to heat by friction.Brake pads are the parts of a car's braking system that actually take the brunt of the force necessary to stop the car. In a disc brake system, the brake pedal activates a hydraulic line which the caliper squeezes down on the brake pads against the rotors. Brake pads are positioned between the calipers and the rotors to absorb the energy and heat, and then provide enough grip to stop the car.
5. What is ABS?
ABS (Anti-lock Systems) was originally developed for aircraft braking systems. When used properly, an antilock brake system (ABS) is a safe and effective braking system. ABS allows the driver to maintain directional stability, control over steering, and in some situations, to reduce stopping distances during emergency braking situation, particularly on wet and slippery road surface. To gain this safety advantage, drivers must learn how to operate their ABS correctly.
An antilock braking system works with the regular or foundation brakes on your vehicle. ABS simply keeps your base brakes from locking up. In vehicles not equipped with ABS, the driver can manually pump the brakes to prevent wheel lockup. In vehicles equipped with ABS, the driver's foot remains firmly on the brake pedal, allowing the system to automatically pump the brakes.
Why is that important?
When your brakes lock up on wet and slippery roads or during a panic stop, you lose steering control and your vehicle can spin. Rear wheel ABS prevents wheel lockup so that your car stays in a straight line. If your car has ABS control on all four wheels, you also keep steering control. If you have steering control, it is possible to avoid a crash by steering around hazards if a complete stop cannot be accomplished in time.
How do I know whether my vehicle has ABS?
Most new car models offer ABS as either standard or optional equipment. There are different ways to find out whether your car has an antilock brake system:
- Read your owner's manual
- Check your instrument panel for an amber ABS indicator light after you turn on the ignition.
- When you buy, lease or rent, ask your dealer or rental car company.
Will I notice anything when the ABS is working?
In many vehicles, drivers may experience a rapid pulsation of the brake pedal--almost as if the brakes are pushing back at you. Sometimes the pedal could suddenly drop. Also, the valves in the ABS controller may make a noise that sounds like grinding or buzzing. In some cars you may feel a slight vibration--this means the ABS is working. It is important NOT to take your foot off the brake pedal when you hear noise or feel pulsations, but instead continue to apply firm pressure.
Does ABS change the way I should use the brakes?
You should not pump your brakes if you have ABS. Just hold your foot firmly on the brakes pedal and remember that you can still steer.
1. What is Friction?
Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. It is not, however, a fundamental force, as it originates from the electromagnetic forces and exchange force between atoms. In situations where the surfaces in contact are moving relative to each other, the friction between the two objects converts kinetic energy into heat (atomic vibrations). Friction between solid objects and fluids (gases or liquids) is called fluid friction. See also aerodynamics and hydrodynamics.
Friction is an extremely important force - it propels automobiles and other ground transport and holds nails, screws and nuts, along with many other uses.
2. What is coefficient of friction?
The coefficient of friction (also known as the frictional coefficient) is a dimensionless physics value which describes the ratio of the force of friction between two bodies and the force pressing them together. The coefficient of friction depends on the materials used -- for example, ice on metal has a low coefficient of friction (they slide past each other easily), while rubber on pavement has a high coefficient of friction (they do not slide past each other easily). Coefficients of friction of a tire on concrete may have a coefficient of friction of 1.7. Brake pad coefficients are generally between 0.3 and 0.7. Magnetically attractive surfaces can have very large friction coefficients, and glued or welded together surfaces have infinite friction coefficients.
Coefficient of friction can vary depending on the type of material used for the brake rotor. Brake pads are typically concerned with dynamic coefficient of friction, or the coefficient of friction measured while the vehicle is moving. Coefficient of friction may change as the brake system is required to perform through different applications. Here are a few of the main characteristics, the characteristics can be minimized or maximized.
- Speed Sensitive- Coefficient of friction typically drops as the speed of the vehicle increases.
- Temperature Sensitive-Coefficient of friction typically drops as the temperature of the brake system increases.
- Pressure Sensitive-Coefficient of friction typically drops as more clamp force is generated.
Sliding (dynamic) friction and static friction are distinct concepts. For sliding friction, the force of friction does not vary with the area of contact between the two objects. This means that sliding friction does not depend on the size of the contact area. The force of friction is always exerted in a direction that opposes movement (for kinetic friction) or potential movement (for static friction) between the two surfaces.
Static friction (informally known as stiction) occurs when the two objects are not moving relative to each other (like a book on a desk). The initial force to get an object moving is often dominated by static friction. The static friction is in most cases higher than the kinetic friction. Rolling friction occurs when one object "rolls" on another (like a car's wheels on the ground). This is classified under static friction because the patch of the tire in contact with the ground, at any point while the tire spins, is stationary relative to the ground.
Kinetic (or dynamic) friction occurs when two objects are moving relative to each other and rub together (like a sled on the ground). The coefficient of kinetic friction is typically less than the coefficient of static friction. From the mathematical point of view, however, the difference between static and kinetic friction is of minor importance: Since friction is always exerted in a direction that opposes movement, kinetic friction always does negative work.
Note that kinetic energy increases with the square of the velocity (E = ½m·v2 relationship). This means that if the speed of a vehicle doubles, it has four times as much energy. The brakes must therefore dissipate four times as much energy to stop the vehicle.
Examples of kinetic friction:
- Sliding friction is when two objects are rubbing against each other. Putting a book flat on a desk and moving it around is an example of sliding friction
- Fluid friction is the friction between a solid object as it moves through a liquid or a gas. The drag of air on an airplane or of water on a swimmer are two examples of fluid friction.
3. What are thermal characteristics?
Engineering brake systems to handle such high temperatures is just as (if not more) important as engineering them to be powerful braking systems. There are four key elements for a system to handle high temperatures properly (as shown below).
- Surface Area: The more surface area on a brake system the better heat dissipation will be. Cooling veins (vents) are used in systems where reducing operating temperatures greatly increases surface area.
- Thermal Mass: A properly engineered brake system must be sized appropriately for each individual vehicle; to have the ability to provide enough power for a vehicle and to have enough material mass to properly handle the temperatures that specific car can create under heavy braking situations. To remove material from a system for size and weight reduction purposes, will also remove material that would have helped absorb heat and diffuse heat generated by braking. This is not recommended by Carbotech.
- Material Selection: Material selection is important in trying to control where the heat goes once generated. Using insulators can help prevent heat from being conducted to the brake fluid. Also in saying that, heat conductors can also be utilized to draw heat away from critical components.
- Cooling Air: Getting air to keep flowing on the brake system can also dramatically help reduce operating temperatures as well as improve performance. Open bridge calipers are becoming more and more popular do the ability to allow air to flow through the caliper and remove heat from the braking surface.
1. What is brake modulation?
Modulation is the process of a driver accurately controlling the amount of brake power required without locking the wheel. Brake modulation is having the ability to consistently increase and decrease the amount of bite from your brake pads at will. The driver has complete control of his/her brake pedal at all times. By controlling the amount of force being applied by the calipers, the driver can use the brakes their advantage in the braking zone and into the first part of the corner. It’s as if the brake pedal is giving feedback to the driver which can be beneficial to a drivers lap times, and therefore help you keep your race car under control and on the track.
As many top level and pro drivers will tell you, being able to modulate and trail brake into the first part of the corner is essential to producing the fastest possible lap times. Yes, we were all taught to brake, down shift, and then turn into the corner. That is the best way to start off, and that’s probably the safest way to start your racing career. But the fact is that there are truly only a handful of corners where you do all the braking before turning in. To run with the best you need to learn how to keep modulating your brake pedal as your entering the first part of a corner. Modulation is what Carbotech built its solid reputation on. Modulation is a cornerstone for Carbotech Performance Brakes.