Any vehicle that has brakes (whether it’s a motorhome, towing vehicle, or trailer) can have its brakes glaze… and it can drastically reduce your ability to come to a stop, posing a very serious danger to you and anyone else on the road near you. But what are glazed brakes, and how do brakes develop this condition? In this post, we take a look at the meaning of the term “glazed brakes,” tell you how the phenomenon occurs, and how you can prevent it from happening to your brakes.
What Are Glazed Brakes?
First, let’s start with a brief description of how brakes work. Whether they’re hydraulic- or air-powered, discs or drums, all automotive braking systems work by squeezing/pressing a component that has a friction material (the brake pads/shoes) against a metal disc/wheel/hub. That friction resists the wheel’s spinning, slowing, and then stopping, the vehicle.
Disc brakes use brake pads that are squeezed against the disc, while drum brakes use shoes that are pushed out against the inside of the drum. Both slow down and stop your vehicle.
When used and maintained normally, your brakes will provide years of reliable service. But the brake pad friction material has a heat limit. When that limit is exceeded (usually from excessive use of the brakes, like when slowing a heavy RV on a steep downhill… or if you apply the brakes too lightly for a long time), the material can harden and take on a glazed appearance. The term “glazed brakes” refers to the hardening or crystallizing of the brake’s friction material caused by exposure to this kind of excessive braking temperature.
If only light glazing occurs, this condition can be harmless and will self-correct over a few hundred miles of driving and normal brake use, resulting in the disappearance of the glazing (as it’s eroded off the surface of the brake pad). However, if deep glazing occurs, the effectiveness of your braking system will be reduced (resulting in longer braking distance and less stopping power when needed), and the brake pads/shoes might be damaged beyond their ability to self-correct and must be replaced.
When examining your brake pad(s), look for signs of them being shiny/glassy. That’s an indication that they are glazed and need to be replaced for your safety.
It’s critical to replace glazed brake pads for safety reasons, as failing brakes can lead to a very dangerous situation when you need them most. Additionally, other brake system components can be damaged if you continue to drive with glazed brakes.
What Are the Symptoms of Glazed Brakes?
If you notice any of the following symptoms, you may be experiencing glazed brakes:
Increased Stopping Distance
The distance a vehicle travels from the time you step on the brake pedal to the time the vehicle comes to a complete stop is called the stopping distance. Stopping distance is affected by many things, including road conditions, speed, the weight of the vehicle, and the condition of your brakes and brake components.
Glazed brakes can cause increased stopping distance, which has the potential to result in an accident.
Because brake pads are one of the brake components that are most directly involved in your vehicle’s ability to slow/stop its movement, a glazed brake pad can increase your braking distance and decrease your stopping power, putting you at increased risk of an accident.
Vibration When Braking
In addition to affecting brake pads, glazing can also transfer to rotors/drums (the heat caused by braking can actually melt some of the friction material from the pads/shoes, leaving it stuck to the opposing metal). If this occurs, you may notice your brakes shuddering when you apply them. This vibration is the result of the brake pad materials building up on the rotor in an uneven manner.
When you depress the brake pedal, if you feel the brakes pulsating or vibrating, your brake pads or rotors may be compromised. This vibration could be caused by glazing or by another brake issue (like a warped rotor) that needs to be addressed quickly.
Decreased Performance of Brakes
Glazing results in the brake pad friction materials becoming glassy and smooth. When this occurs, the brake pads and rotors are unable to provide the necessary friction to stop the vehicle. Obviously, this can result in a dangerous situation. So if you notice that you suddenly need to apply more pressure to your brakes in order to stop as quickly as before, your brakes may be glazed.
What Causes Glazed Brakes?
Typically, the development of glazing on brake pads is caused by one or more of four factors.
Riding the Brakes
When someone drives with a foot on the brake pedal (to the extent that the brake lights are illuminated), this is often referred to as “riding the brakes”. This is a very bad habit and can very easily lead to glazed brakes because the pads and rotors are in near-constant contact. Not only does this increase the temperature in your braking system (which could result in glazing), but it’s also likely to prematurely wear out the brake pads and other brake components.
Riding the brake pedal can result in glazed brakes due to the increased temperature to the braking system caused by this bad driving habit.
Hard Braking
Another bad habit that can cause glazed brakes is hard braking, especially at higher speeds. When you apply your brakes hard while driving, the temperature of the braking system increases. If this happens somewhat frequently, it can result in glazing because the brake pad materials deteriorate with regular exposure to the increased temperatures.
If you brake hard and notice a burning smell, be alert to the fact that the brake pad material may have been damage and glazing may have occurred.
Constant Downhill Braking
As you travel down long and/or very steep hills, if you constantly apply/hold the brakes, you’re probably increasing the temperature of your braking system, which, in turn, can cause glazing. Of course, it can be necessary to slow your vehicle while moving downhill. However, if you’re traveling down a steep decline, downshifting to a lower gear and/or activating your motorhome/truck’s exhaust or engine brake is a preferable manner of slowing your vehicle without damaging the brakes.
PRO TIP: Years ago, professional truckers were taught to keep steady, light pressure on the brake pedal if needed to avoid overspeeding in long, steep downhill conditions. As this practice can overheat the brakes, that guidance has been replaced with a safer technique: repeated very firm brake applications for shorter durations (5-10 seconds) to substantially reduce speed, alternated with no brake application to allow the brakes to cool. This technique also provides the opportunity for downshifting each time the speed has been reduced.
A Stuck or Damaged Brake Caliper
If you have a stuck or damaged brake caliper/shoe, it can cause uneven wear on the friction material, potentially leading to glazing. A stuck caliper/shoe can either continuously push on the brake pad/shoe (wearing it out prematurely and increasing the likelihood of it glazing) or it can result in one side/part of the pad/shoe being applied with greater force (again, increasing its temperature during longer/harder brake applications). This can not only reduce your stopping power but can also cause pulling and/or soft brakes.
A stuck brake caliper can lead to uneven wear on the brake pad which can, in turn, lead to glazing.
For more information on what affects the lifespan of your brakes, see our post addressing the question, “How long do RV brakes last?“.
How to Prevent Glazed Brake Pads
The best way to prevent glazed brakes is to use good braking habits. This means not riding the brakes, refraining from repeated/excessive hard braking, and downshifting (and using your engine’s exhaust/engine brake if available) to control your vehicle’s speed on a long downhill slope.
It’s also important to tend to regular brake inspection and maintenance to make sure your brake components are in optimal condition. This will not only ensure that your brakes last as long as possible but can also prevent an accident and could even ultimately be life-saving.
For more great tips on driving an RV that’ll keep you safer on the road, we recommend checking out our posts on how to drive an RV (off-tracking and rear overhang) and how to adjust rv mirrors and lane control.
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Albert Bartkowski
Sunday 4th of August 2024
Also remember that brake pads and rotors come in various degrees of performance and $$$. Most companies that make brake products produce brake pads made for specific and higher end applications, as for higher performance, racing, towing, etc. I use pads made for towing heavy loads, which will not give you as much pad life, but stop loads better. But again-$$$$!