Lots of conditions can cause your brakes to drag including: warped rotors; bad master cylinder; residual pressure valve in system; calipers are not square to rotors; tapered brake pads; and debris in the caliper that’s not allowing the brake pads to retract properly.
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 reasons 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; which is also known as Noise, Vibration and Harshness (NVH) a common term in the automotive industry.
Oscillating feedback is caused by 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 feedback.
Warping can be caused by not properly torqueing 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. 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. This is why the parking brake should never be applied at the end of a track session.
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.
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.
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 doesn’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.
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.
In most cases this is a result of the brake fluid boiling. It can also be caused by faulty master cylinder or a leak in either the caliper or brake lines. Sometimes this could be the result of an undersized brake system.
If you find yourself having to push very hard on the brake pedal, there are a number of things that might not be going right. It is possible that the brake pads and/or rotors were not properly bedded. You might also have glazed brake pads and/or glazed rotors. Or you may have chosen the wrong brake pad compound for your application, a master cylinder that is too large, or an insufficient pedal ratio.
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/moisture in the lines.
If your brake pedal slowly sinks to the floor, 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 definitely have a leak somewhere. The other option (if you don’t have a leak) is that you have a bad master cylinder.
With all Carbotech compounds you will have to apply a little bit more pedal pressure to get the maximum amount of bite from the brake pads. That’s because you have the ability to modulate your pedal with our Ceramic Kevlar compounds. That’s a huge advantage to any driver, especially a driver who has a good feel for their car. The more you can modulate your brakes the more car control you have under braking. The more control a driver has under braking gives the driver an edge in the braking zone and the first part of a corner. Control which in the end helps you attain faster and more consistent lap times.
Go Deep™ or as we like to say today “Brake Last, Finish First!™”