What is Brake Fade and What Causes It?
If you apply the brake pedal and your vehicle doesn’t slow down as quickly as you expect it to, it can be more than just a little concerning. Poor braking performance can be caused by many things like worn-out brake pads, but it isn’t always a sign that you need to replace your brakes. It could be brake fade.
There can be a few causes for brake fade, and the symptom feels the same. Thankfully, correcting the problem is seldom expensive and it might not need a repair at all. Here’s what you need to know.
What Is Brake Fade?
Brake fade is an unexpected reduction in braking performance. When you press the brake pedal, you’ll notice that it takes longer for your car to come to a stop than you’re used to. Usually, there’s an increase in effort on the pedal to achieve the stopping power you need.
If you’ve ever felt the need to press the brake pedal with both feet after driving down a hill, your car is creeping forward in traffic when you’re trying to hold it at a stop, or it feels like your pedal is spongy and travels further to the floor, you’ve experienced brake fade.
The unpredictability of brake fade can result in performing a brake inspection or taking it to the shop to have your brakes checked, but there typically aren’t any noticeable problems. And after the car sits for awhile, your brakes will work normally – once they cool down. Then, after driving under just the right conditions, it might happen again.
What Causes Brake Fade?
Brake fade can be frustrating to diagnose. What causes brake fade? There are actually three distinct reasons for the exact same symptom.
The most common cause for brake fade is from overheating due to friction on the brake pads. It’s what happens when the heat generated by braking can’t dissipate well before subsequent brake applications. Temperatures on the brake pads normally stay below 400 degrees Fahrenheit, but it’s possible with prolonged or extreme use for the temperatures to exceed 700 F.
For standard-duty brakes, the binder or resin in the friction material can begin to melt. When that happens, it behaves as a fluid or lubricant between the brake pad and the rotor, and they don’t grab like they should on application. When the brakes cool, the binder can harden and adhere as a microscopic layer on the pads and rotors, and anytime there are higher than normal temperatures, the condition can resurface.
The common types of brake fluid used in passenger vehicles, DOT 3 and DOT 4, have a dry boiling point of 401 F and 446 F respectively. But when the fluid does boil, little bubbles form in the fluid that compresses much easier than liquid, causing a spongy brake pedal and brake fade.
It isn’t normal for fluid fade to occur with new fluid because of the tolerance for high temperatures. However, brake fluid is hygroscopic, meaning it absorbs water vapor to prevent corrosion inside the system. When the brake fluid has absorbed moisture and contains 3.7% water, it boils at a much lower temperature. This is known as the wet boiling point. Under heavy braking conditions, it’s possible to reach the wet boiling point in the brake lines. That’s when fluid fade occurs.
Gases are trapped in the friction material during manufacturing. When these gases are released as the brake pads get hot, they create a buffer between the friction layer and the brake rotor. Essentially, it’s the same premise as a car hydroplaning on a wet highway, and the pads can’t get enough grip on the rotor.
Seldom will green fade become evident anymore as manufacturing criteria and materials used are much higher quality than they used to be. But it can still happen, and when it does, it feels like the car won’t stop no matter how hard to press the brake pedal.
Green fade tends to dissipate after the brake pads have come up to temperature a few times and off-gassing has been completed.
How to Prevent Brake Fade
It might seem like a problem you’re unlikely to encounter, yet you’ll keep it that way by preventative measures, whether you’re aware of it or not.
1. Change the brake fluid around every two years
Both DOT 3 and DOT 4 brake fluids can absorb up to 2% moisture content in a single year. Reaching the 3.7% threshold for the wet boiling point can occur in under 24 months. While that doesn’t assure brake fade will happen, it’s more likely to occur.
2. Use the appropriate rotors for your performance
To avoid friction fade, it’s imperative to keep your brakes within normal operating temperatures. If you plan to race, tow heavy loads, or otherwise tax your braking system regularly, disperse as much heat as possible by ensuring you have good-quality rotors installed. Slotted or drilled rotors can help reduce temperatures at the brake pads.
3. Break in new brake pads
To avoid green fade, get any gases in the friction material to release under controlled conditions. It’s often done by riding the brakes immediately after installing new pads to get them very hot. It’s best to follow the manufacturer’s break-in procedure, though.
If you’ve had brake fade and want to install new brakes, shop at AutoZone. Find high-quality brake pads and rotors at a great price from top brands like Duralast. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.
FAQ/People Also Ask
Most brake fade symptoms are caused by friction fade, where the pad is overheating and the binder begins to melt.
Excessive moisture in the brake fluid, overheating brake pads, and off-gassing from new brake pads can all cause brake fade.
To correct brake fade, you’ll need to identify the cause first. Typically, you’ll either need to replace brake pads and rotors or change the brake fluid.
Brake fade falls into three categories: friction fade, fluid fade, and green fade.
Yes, brake fluid can cause fade if it contains excessive moisture. It can boil in the brake lines and fail to compress properly.