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Troubleshooting Brake Procedures

  1. Why do I have to push really hard on my brake pedal?
  2. Why do brake rotors crack?
  3. Why did I lose my brake pedal during the race?
  4. What is brake fade?
  5. What causes rotors to warp?
  6. What causes brakes to make noise (squeal)?
  7. What causes brakes to drag?
  8. What causes a spongy pedal?
  9. My brake pedal slowly sinks to the floor, why?
  10. Why am I getting oscillating feed back?
  11. Pedal is low when I first step on it, if I pump it the brake pedal comes up, why?

Q: 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

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Q: 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. 

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Q: 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.

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Q: 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.

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Q: 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.

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Q: 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.

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Q: What causes brakes to drag?

  1. Warped rotors.
  2. Bad master cylinder.
  3. Residual pressure valve in system.
  4. Calipers are not square to rotors.
  5. Tapered brake pads.
  6. Debris in the caliper that’s not allowing the brake pads to retract properly.

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Q: 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. 

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Q: 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.

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Q: 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.  

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Q: 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.

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