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Brake Pads

Q:  What kind of brake pads should I use ?

A:  The best type of brake pad for any car will depend on both how the vehicle is operated and the vehicle type. For example, factors like vehicle weight, brake temperature, and how the vehicle will be used should be considered when choosing the proper brake pad. Wilwood stocks multiple brake pad compounds for most popular cars and trucks, and has the right brake pad for your street performance application. Click here for more information on Wilwood’s complete line up of brake pad options.

Q:  Do you make a pad that will work equally well for both street and track use ?

A:  The short answer is no pad will work "best" in both environments; there will always be a compromise in one area of operation. Pads are asked to do a number of different tasks in different situations. The following are things you should consider to help you pick the best pad.

  • Stopping performance when cold. How well does the pad grip on the first stop when the system is at ambient temperature?
  • Stopping performance when hot. How the pad reacts in higher temperature such as on the track?
  • Pad Life. How long will the pads last in a given driving environment?
  • Rotor Life. How aggressive is the pad on the rotor.
  • Noise. Does the pad squeal?
  • Dust. How much dust does the pad generate, how easy is it to clean?
If you run one pad on both the street and the track, you will have to compromise performance in one way or another on all the above. We suggest changing to a track worthy pad for track events, with a proper bed-in before the event. The system will need to be bedded-in again when the street pads are re-installed for the street. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  Will larger brake pads improve my stopping distances ?

A:  Not necessarily. A larger pad of the same compound in the same location as a smaller pad will not yield shorter stopping distances. The amount of pressure applied, the pad friction coefficient, and the diameter of the rotor at which that pressure is applied, determine the torque reaction, or stopping force. A larger pad does not apply more pressure, only the same pressure over a bigger area.

The size of the pad does matter in terms of heat capacity and wear rate. A larger pad will absorb more initial heat, hence less thermal shock, and have better wear characteristics resulting in longer pad life.

Q:  How do I retract the caliper pistons to change pads ?

A:  Before new pads can be installed, the pistons need to be pushed back into the caliper body.

There are several ways you can accomplish that without requiring special tools. However, be very careful during retraction because you don’t want to damage the face of the piston where it contacts the backing plate of the pad. (Normally the rotor will be loose on the hub with the wheel removed.) By working the rotor back and forth, you will be able to push the pistons back enough to remove the used pads without risking damage to the piston(s). This is particularly important in the case of significant rotor wear, in which case there is a raised ridge on the outer edge of the rotor face that makes sliding the pad out of the caliper difficult.

The used pads being removed from the caliper can be used as a tool to “lever” the pistons back into their bores. Remove one pad from the caliper while leaving the other used pad in place. Rotate the removed pad 90 degrees and re-insert it halfway into the caliper perpendicular to its normal axis. The center of the pad will rest on the outer edge of the rotor, creating a fulcrum on which the pad can rotate. Keep the pad face toward the rotor and using the pad as a lever, press both pistons in at the same time. It is important to retract both pistons at the same time so they are compressed evenly. If you have trouble retracting the pistons, you can open the associated bleed screw with a hose leading to a tray or bottle of fluid, and it will ease the resistance. Remember, you will need to bleed the system if you open the bleed screw. Push the pads in as far as possible, close the bleed screw, remove the used pad and install the new pad. Repeat the process on the other side of the caliper. You can also use other tools to push in the pistons, including special tools designed specifically for that purpose; however, unless you replace pads on a regular basis, it is not worth the cost to purchase them.

One final caveat; keep an eye on the brake fluid level in the master cylinder reservoir. If the system was bled and topped off when the pads were worn, you might push enough fluid back through the system to overflow the master cylinder. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  Does my brake pad bedding process change at all if I have e-coated rotors ?

A:  No, the bedding process is the same. Remember, the proper break-in of pads and rotors is extremely important. Not doing it properly, can cause permanent damage to rotors and adversely affect overall brake performance. Pads and rotors interact with each other to provide efficient brake performance. The break-in or bed-in procedure is done to condition the pad/rotor interface. Depending on the pad being used, more or less pad material is uniformly transferred onto the disc as a thin film. The resins and bonding agents in some pads need to be heat cycled to work properly as well. By not properly bedding in pads, uneven pad material deposits can occur that may cause a vibration. Improper wear characteristics may also show up on either the pads, or rotors, or both. For more information on bedding, please consult Wilwood's Tech Tip Guide. You can also contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  What is "uneven pad deposition," and how does it affect my brake performance ?

A:  Before new pads can be installed, the pistons need to be pushed back into the caliper body.

The vast majority of modern brake pads are what is referred to as an adherent type of pad. The pad is designed to transfer a layer of pad material onto the rotor. When a sufficient and even layer of pad material is adhered to the rotor face, the pad material on the rotor, interacting with the similar material on the pad, creates the most efficient friction mechanism. The "like" materials, breaking against each other on a molecular level, provide the best braking performance. Problems occur when the pads are not properly bedded-in, i.e., an even layer of pad material is not deposited on the rotor and the brakes are used aggressively, or when the pads are overheated, e.g., using street pads on the track. The pad transfer occurs most efficiently at the pads optimal operating temperature. That means a higher temperature pad needs to be hotter to properly transfer material. If you have a high-performance pad and never run it hot enough to get a proper layer of material onto the rotor, it will never be properly bedded-in. Thus, even after several hundred miles of "normal" street driving, you can get uneven deposits on the rotor causing a vibration when you engage in some form of racing and heat the brakes. The other common scenario is over-heating the pads even if they are properly bedded-in. In this case, the pad material starts to break down and smear onto the rotor face, again causing un-even deposits.

The other problem that occurs is when the system is really hot and you come to a complete stop and leave your foot on the brake pedal. In this instance, you get what is called "pad imprinting" where a small layer of material breaks off from the surface of the pad and literally can be seen as an imprint of the pad on the rotor face. This can occur in any state of the bed-in process. All of these scenarios leave very small, uneven layers of material on the rotor. All it takes is a few 10/1000's of an inch. It starts out almost imperceptibly, but as the pads start to skip over the high spots, more material is deposited on those areas, ever increasing the vibration until it becomes quite noticeable, even days after the event that started it occurred. The best way to avoid these problems is the proper bed-in of the system initially, and using the proper pads for your exact driving conditions.

Q:  I have a shudder or vibration under braking. What should I look for and how can I fix it ?

A:  In order to better understand the likely cause of shudder and/or vibration, please see the above FAQ relating to un-even pad deposition. Obviously, turning the rotors will take care of it, but you will be shortening the life of the rotor and decreasing its ability to absorb and control heat, as there will be less mass in the rotor after turning. We have had very good success running an aggressive track pad at lower temperatures on the street in order to scrub-off the rotor surface. We have found the Polymatrix B race pad to be very effective. At lower temperatures it is very abrasive and does not become adherent until it reaches its optimal operating temperature. If it is used with a few firm stops at a time, not getting too hot so that you only remove material, not transfer more; it will often remove the source of vibration. WARNING: Do not leave an abrasive pad in the caliper longer than necessary to solve the problem. As soon as the problem goes away, change back to your street pad and re-bed them. Your rotors can be destroyed in under a week by leaving the abrasive track pads in on the street. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  Where can I get replacement brake pads for my Wilwood calipers ?

A:  Wilwood has a worldwide dealer network that stocks and sells replacement parts. A quick Google search can help you find a stocking dealer such as a local high-performance speed, hot rod or race shop, or you can buy them on-line through our website. You can also contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  Should rotors be turned before replacing brake pads or after a set amount of road service ?

A:  Not if they are still serviceable. In fact, the best way to bed your new pads is with a rotor that has already been bedded. The rotor is basically the radiator for your brake system. The larger the rotor for any given design, the better it cools. Each time you turn a rotor, you remove material; therefore, you remove some of its ability to cool. You should regularly inspect your rotors for conditions such as cracks or excessive wear and immediately replace them if they are defective or out of tolerance. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:  Why do my brakes clunk or squeal when I apply them ?

A:  Some of the noises can be minimized; others are an unavoidable result of the incredible friction levels obtained in today's high-performance racing brake pads.

Sounds that are mechanical such as clunks, bangs and rattles may be caused by missing or worn out "anti-rattle" devices that are designed to place a small amount of tension on the brake pad in the caliper, limiting its free play movement. The easiest way to silence these noises is to replace any missing or damaged anti-rattle clips.

Squeal may emanate from a number of sources; however, it most commonly comes from a harmonic that develops between the caliper piston and the pad backing plate. Applying our noise absorption shims usually reduces the backing plate to piston squeal. Our noise absorption shims are an elastomeric dampening material over a steel shim, which installs between the pistons and backing plate. Noise absorption shims are available for both our Dynalite and Superlite brake pads. If further noise reduction is required, you may want to switch to our Polymatrix Q compound pads. Our Q compound pads were specifically designed for low noise and low dust. Accomplishing the goals of very low noise and dust requires that the pads have a lower coefficient of friction than our standard pads, and therefore you may notice a slight decrease in braking performance. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Wilwood Engineering, Inc
4700 Calle Bolero
Camarillo, CA 93012
Phone: (805) 388-1188
Fax: (805) 388-4938

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