A brake drum is a wide yet short cylinder attached to the wheel. When the brakes are engaged, the friction material on the brake shoes (or pads) makes contact with the brake drum to slow down or stop your vehicle.
As a result, brake drums get hot through regular use.
But occasionally, they can overheat.
Why does this happen?
This Article Contains
- Brake Drum Hot to Touch? Here’s What Happened
- How Does an Overheating Brake Drum Affect Your Car?
- 6 Hot Brake Drum FAQs
Brake Drum Hot to Touch? Here’s What Happened
Brake drums become hot because of friction. The brake system converts kinetic energy into heat energy through contact between each brake shoe and the drum. This contact is what reduces the turning of the wheel.
How much heat is normal?
Typically, hot brake drums range in temperature from 150°F to 400°F when operating.
But sometimes drum brakes can overheat, reaching temperatures of 600°F or more.
Why does this happen?
Besides aggressive driving, there are three main causes:
- Warped brake drum: The surface of the drum is either uneven or rough due to the accumulation of dirt and brake pad material. This is typically a result of high temperatures related to strong braking.
- Seized wheel cylinder: Over time, failing dust boots make the wheel cylinder rusty or dirt-filled. The dirt or rust then causes the pistons to seize, keeping the brake shoes in contact with the drum. This is known as brake drag.
- Incorrect adjustment: Poorly adjusted brakes can cause excessive contact between the brake drum and brake shoe. In extreme cases, poor brake adjustments can cause the rear wheels to lock up.
Note: A faulty wheel bearing can cause your brake drum to get hot, too. The bearing connects the wheel to the axle and enables the wheel to rotate smoothly. However, a faulty wheel bearing could cause the wheel hub to turn extremely hot, and this heat could transfer to the brake drums.
A disc brake produces less heat due to the brake design. The brake caliper, rotor, and brake pads are exposed to air, allowing them to cool off quickly.
Quick fact: Many modern cars use both types of brakes, with the drum brakes on each passenger side and driver-side rear wheel and the brake discs on the front wheels.
Using a rear drum brake saves costs and is also less complex to produce.
Now that we have discussed why brake drums get hot and sometimes overheat, let’s look at what this means for your vehicle.
How Does an Overheating Brake Drum Affect Your Car?
Mostly, the heat from braking doesn’t affect your vehicle significantly. But, in extreme cases, overheating brakes can impact your car in several ways:
1. Abnormal Brake Functioning
There are three ways in which overheating brake drums can affect brake functioning:
- Fading brakes: “Brake fade” refers to the reduced stopping power of the brakes due to repetitive use. If this happens, your brake pedal may feel “spongy.” A spongy brake may also be the result of hot brake fluid.
- Smoking brakes: Smoke can often result from excessive heat. You may also notice a burning smell accompanying the smoke.
- Squealing brakes: When the brakes get worn, they can often squeal when the metals grind together during braking.
2. Heat Checking Drums
“Heat checks” refer to small, thin cracks on the drum brake surface. They are a result of repetitive heating and cooling of the brake system.
Usually, they will disappear as you continue to use the brakes.
However, they can develop into deeper cracks. If the deeper cracks are caught too late, they can result in the entire drum cracking.
3. Cracked Brake Drum
Extreme braking creates a continual heating and cooling cycle that can stress the brake drum metal — and your brake drum can eventually crack under braking force.
When it comes to cracked brake drums, there are two likely causes: slamming on the brakes at high speed and a skewed brake system. It’s always a good idea to examine your brakes for heat checks or major cracks, especially if you apply your brake aggressively.
4. Excessive Wear and Tear
Excessive wear on the drums often results from a buildup of dirt and debris (brake dust) in the drum braking system. While a backing plate on disc brakes helps prevent brake dust and other dirt from accumulating on suspension parts, the drum brake backing plate actually keeps the brake dust inside.
Once brake dust and debris get inside the brake system, they’ll eventually cause damage to the friction material.
But that’s not the only cause of excessive wear.
Bad driving habits and excessive heat also significantly impact the longevity of your braking system – particularly late and aggressive braking.
5. Shiny Drums
Too much drag on your brakes can cause them to wear down faster. Brake drag leaves a surface that looks shiny, polished, or reflective.
What causes a dragging brake?
A dragging brake is typically results from faulty springs. Brake drag can also result from a frozen parking brake cable or overextended self adjuster.
6. Blue Drums
A bluish color on the braking drum surface indicates that the drum has experienced very high temperatures. In this case, it is highly recommended you consult with a mechanic, as a braking failure could be likely.
What causes this to happen?
Several factors include defective return springs, brake system imbalance, and repetitive hard stops.
7. Out of Round Drums
Typically, your brake drum should be perfectly circular. So if there are different diameters along its surface, then it’s considered “out of round.” Essentially, the brake drum is warped, resulting in poor clearance between the brake shoe and drum.
Why does this happen?
Out-of-round drums occur mostly due to excessive heat and poor brake assembly.
You know how overheating brake drums affect your car, so let’s dive into some other drum brake questions.
6 Hot Brake Drum FAQs
Here are answers to some common brake drum FAQs.
1. How Do Brake Drums Work?
When the brake pedal is applied, the master cylinder converts the pressure from the brake pedal to hydraulic pressure.
The pressure pushes the pistons, which, in turn, presses the brake linings into the brake drum. This causes friction which serves as a stopping force on the wheel.
How are disc brakes different from drum brakes?
Disc brakes utilize a rotor (brake disc) that attaches to the wheel and a brake caliper that covers a section of the rotor. Inside the brake caliper, two brake pads clamp against the rotor when the brakes are engaged to stop the wheel from turning.
While disc brakes utilize a different mechanism, the brakes are engaged through the master cylinder with hydraulic pressure.
2. Is an Overheating Brake Drum Dangerous?
Excessive heat in the brake drum can cause brake fade, essentially reducing braking ability.
Brake fade is more common in drum brakes, as their closed design traps heat more than a disc brake.
Naturally, reduced braking ability is dangerous and should be treated by a mechanic.
3. What are the Other Signs of Overheating Brake Drums?
Typically, other signs of overheating brake drums include smoke and a burning smell.
In addition, if your brake is fading, you will notice that your pedal feels “spongy” when applied, which can also result from hot brake fluid.
Lastly, you may notice your brakes squealing when they are in use. This is often because of “glazing,” which refers to early brake wear and a loss of braking friction.
4. What Should I Do If My Brake Drum Heats Up?
While normal heat in a drum is nothing to worry about, you should immediately stop driving if you notice an overheating brake. Ideally, you should have your car towed and repaired by a reputable mechanic.
But what if I have to drive?
Keep a low speed to compensate for the lack of braking power, and take your car to a mechanic ASAP.
If your brakes fail while driving, you may have to apply the parking brake(emergency brake or e brake) to slow down and stop your car.
5. How Can I Prevent an Overheating Brake Drum?
Generally, good driving habits will prevent your brakes from overheating. Essentially, anything that reduces pressure on your brakes, including:
- Leaving enough distance to brake slowly
- Avoiding slamming your brakes
- Using engine braking when driving downhill
6. Do Front Brakes Get Hotter than Rear Brakes?
Front brake drums will likely be hotter than the rear driver and passenger side drums. Your vehicle’s center of gravity shifts forward during braking, meaning less pressure on each rear wheel.
So the rear brake does less work to stop the wheel from turning, meaning less heat buildup on the rear drum.
Brakes produce a certain amount of heat under normal use due to kinetic energy. But overheating brake drums can be a serious problem.
If you notice your brake drums are overheating, reach out to AutoNation Mobile Service!
AutoNation Mobile Service is a mobile mechanic service that comes to your driveway to diagnose and fix your car troubles. Whether it’s a parking brake problem, brake rotor issue, or broken axle, we have you covered!
Here’s why you should choose us:
- Our mobile car repair and maintenance services are available seven days a week
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Get in touch with us, and our experts will drop by to fix your brakes for you!