Braking Fundamentals: Brake Pads, Rotors and Fluid

Car brakesWe cover the basics and explore the science behind brake parts and related accessories.

 

With so many options to choose from, how do you know which brake rotors, pads and/or fluid is best for your vehicle? Step one is to look for guidance in your vehicle’s owner’s manual – and then find more details here.

Function of brake pads

When you push on your car brakes, calipers clamp the brake pads onto the rotors to reduce speed and then stop the vehicle. To do their job effectively, the pads must be able to absorb enough energy and heat. When there is too much wear and or heat, brake pad efficiency is reduced – and so is your stopping power.

Brake pad choices include:

  • Ceramic, composed of ceramic materials; sometimes copper fibers
  • Semi metallic, composed of steel wool and fibers; sometimes brass or copper
  • Organic, composed of glass, rubber and resins

AdvanceAutoParts_Brake_Pads_072114 Function of brake rotors 

Your brake pads clamp down on the rotors (also called brake discs). The lug nuts hold both the rotors and wheel to the wheel hub. When pressure is applied to the brake rotors, it prevents the wheel from spinning – which means that your brake rotors are as important as the pads when it comes to safety.

You’ll need to make several decisions to choose the best rotors for your vehicle, including:

  • Which material is best
  • If you want drilled or slotted rotors
  • If vented or non-vented rotors are better
  • Whether you need a cryogenic treatment for your rotors or not

Most rotors are made from cast iron – more specifically, gray iron – because it disperses heat well, which is important to avoid overheating and brake fade. Meanwhile, racing and other high performance vehicles often use reinforced carbon rotors, similar to those used in airplanes. Carbon rotors need to reach a high temperature before becoming effective so are not good choices for the average car. Other high performance vehicles use ceramic rotors, an innovation first used in British railroad cars. Ceramic rotors are lighter in weight and are stable at high speeds and all temperatures. They are, however, more expensive.

Here is more info: AdvanceAutoParts_Brake_Rotors_Image_072114 Cryogenic treatment

Over time, rotors warp because of heat and usage. If you adjust the warpage through truing, this solves the problem – unless the rotors are too thin, or heat up and warp again. So, your options are to:

  • Replace the rotors whenever needed
  • Replace the rotors and then have them cryogenically treated

When cryogenically treated, rotors dissipate heat much more effectively and maintain their optimal (non-warped) shape for a longer period of time. This means that they need replaced much less often.

Beware of brake fade

Brake fade (the reduction in stopping power after repeated or sustained usage) occurs most often when you’re carrying a heavy load in your vehicle, traveling down a long steep hill or driving at higher speeds. Brake fade can happen in any vehicle that uses a friction braking system because of a build-up of heat, although drum brakes are more at risk since disc brakes can vent heat away more easily. Brake fade can take place in vehicles with braking systems in overall good condition, although regular maintenance can help to prevent this from happening to you. To avoid bad repercussions from brake fade:

1)   When replacing your brakes, choose the highest quality that you can afford.

2)   Watch for “green fade,” which happens when the resin applied to brakes by manufacturers begins to evaporate. This can create a period of time (say, the first 100 miles of usage) when you should be extra vigilant about effective braking.

3)   When braking, tap your brakes instead of continually applying pressure.

4)   Shift into a lower gear when driving downhill, rather than riding your brakes. Shifting to a lower gear tells the engine to maintain a safe speed.

5)   Don’t try to go 70-0. Brake gradually over longer distances.

6)   If you’ve gone through a period of heavy brake use, keep a longer distance between your vehicle and the one in front of you, just in case.

7)   Check your brake fluid regularly and change at least annually.

Choosing the best brake fluid

In the United States, there are four designations of brake fluid that meet the minimum Department of Transportation standards: DOT 3, DOT 4, DOT 5 and DOT 5.1. Each contains a mixture of chemicals with specified dry and wet boiling points. When your brake fluid has just been replaced (with a full bleed), this is called the “dry” boiling point temperature. As water finds its way into the system, the “wet” boiling temperature is the benchmark you should use. Here are more details about brake fluid options, but be sure to purchase one that meets the minimum recommended by your vehicle manufacturer.*

 Editor’s note: Trust Advance Auto Parts for the best selection and values in brakes. Buy online, pick up in-store, in 30 minutes. 

*Note: Silicone Brake Fluid is not compatible with Anti-Lock braking systems, and should be used only if recommended by the manufacturer. Always consult your owner’s manual first. Follow the manufacturer’s recommendations to ensure warranties are not voided.

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  1. What cause breaks to shimmery when applying pressure on pedal

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