While most people know what the brakes on their car are responsible for, a lot of them don’t realize how many different components there are to the braking system, and how those parts can get damaged or worn out. Brake rotors are one of those components, and through use, they can become warped and ineffective.
So what causes brake rotors to warp? The main cause of brake rotors warping is excessive braking at high speeds, which causes the rotors the heat up. When the rotors become too hot, the metal they are comprised of becomes soft and begins to warp, causing the rotors to malfunction.
Warped brake rotors can cause excessive wear of your brake pads and in severe cases, can even impact a car’s ability to brake. Keep reading to find out more about the function of rotors in a car’s braking system and how warped rotors become a problem.
What Are Brake Rotors?
Before we can do into the causes of brake rotors warping, you’re going to need to know a little bit about brake rotors, what they are made of, and how they work.
Brake rotors (also commonly known as brake discs) are large metal discs that are located directly behind the wheels of a vehicle. If you walk alongside a car and inspect the wheels, you can typically see a visible brake rotor.
There are two standard categories of brake rotors:
- Drilled brake rotors: Drilled brake rotors
feature a circular series of drilled holes that help gas, water, and heat to
dissipate from the brake rotor quickly, as well as give the calipers extra gripping
power in wet conditions.
The downside of drilled brake rotors is that the drilled areas can cause the structural integrity of the brake rotors to be weaker than if they were solid, which can lead to degradation or even cracking under harsh driving conditions such as high-speed braking.
- Slotted brake rotors: Rather than having
holes all the way through them, slotted brake rotors feature indentations on
the front surface of the rotor that help to dissipate water, air, and heat for
maximum stopping performance.
Slotted brake rotors are popular on performance vehicles such as race cars but are not typically practical for everyday use because they tend to wear down brake pads very quickly.
The way brake rotors work is that when a car is braking, the car’s brake calipers clamp down on the rotor, and the rotor stops the wheel from spinning. Because they must absorb a ton of friction, brake rotors must be constructed to withstand very high levels of heat.
The heat generated by brake rotors also has to be designed to dissipate quickly because the brakes are used so frequently while driving.
How Do Brake Rotors Work?
Brake rotors work as part of an integrated system along with the calipers and brake pads. When the operator of a vehicle presses down on the brake pedal, this causes the calipers to clamp the brake pads down on the brake rotors. The brake pads push against the moving wheels to slow them.
What Are Brake Rotors Made Of?
The majority of brake rotors available on the market are constructed from gray cast iron. This is because gray cast iron disperses heat well, which is the single most important aspect of brake rotor construction.
While most brake rotors are made of iron, there are also ceramic rotors used that have the following advantages over metallic ones:
- They are lighter to handle
- They are more stable than metallic rotors at high speeds
- They are more stable than metallic rotors at high temperatures
There are many benefits to using ceramic brake rotors over metallic brake rotors, but ceramic rotors tend to be much more expensive than metallic rotors.
Metallic rotors might be less expensive but wear more quickly and produce more brake dust. A good compromise can be semi-metallic rotors, which fall between metallic and ceramic rotors in price and offer some of the advantages of ceramic rotors at a lower cost point.
Another option for rotors is a rust-proof coating, which increases the durability of the rotor as well as maintains its shine for added cosmetic value.
What Causes Brake Rotors to Warp?
When a brake rotor becomes warped, the surface of the rotor becomes rough and uneven. The primary cause of brake rotor warping is excessive amounts of heat build-up when braking. Excessive heat can affect the brake rotors negatively in two ways:
- It can cause the brake pads to break down and
glaze the brake rotors with gripping material, reducing their effectiveness
- Excessive heat allows the brake pad to wear down the rotor surface, which leads to rougher patches on the rotor where the density of the metal is uneven
In either case, the rotors are damaged by excessive heat, and this damage, in turn, affects the stopping performance of the vehicle.
Does Hard Braking Cause Brake Rotors to Warp?
Hard braking alone does not cause brake rotors to warp, as long as braking is done when the car is already driving at a lower speed. However, repeatedly braking from high speeds, such as the maneuvers performed on a racetrack, causes heat to build-up faster in the braking system.
If a driver has to perform an emergency stop and a hard brake with their vehicle at a low speed, such as twenty or thirty miles an hour, this should cause no damage to the braking system.
However, if a driver is repeatedly slamming to a stop from higher speeds such as forty miles per hour or above, this is eventually going to cause the brake rotors to warp.
Why is It Important to Replace Warped Rotors?
There are several reasons it’s important to repair or replace warped rotors when they occur, and some of these include the following:
- Increased wear in the braking system: A
warped brake rotor not only causes brake pads to wear more quickly than
necessary, but it can also cause damage to the brake calipers, which can be a
very expensive mechanical repair.
- Decreased ability to brake: The most
dangerous reason it’s important to replace warped rotors is that allowing this
damage to continue can eventually lead to your brakes failing, which can, in
turn, lead to a serious car accident.
- Increased liability: It is dangerous for the driver of a car with bad brakes in the case of an accident but driving a car with a faulty brake system also makes the driver responsible for any other damage they might cause in a wreck related to the brakes failing. If a person is badly injured or killed as a result of vehicular neglect, civil and criminal charges can even be pressed.
It is sometimes easy to skimp on maintenance for vehicles, especially for those drivers on a tight budget, but the brake system is not a system you want to try and limp along.
If you have issues with your brake rotors, it is a serious safety hazard, and the vehicle should not be driven until the rotors are repaired or replaced.
How to Inspect Brake Rotors for Warping
It can be difficult to tell the condition of a brake rotor just by looking at it on the vehicle. While brake pads have sensors and visible indicators that they are becoming worn, brake rotors are not that obvious in their presentation during an inspection.
Here are a few warning signs to look for when visually inspecting your brake rotor:
- Visible cracks
- Grooves on the rotor
- A lip on the edge of the rotor
- Heat spots
- Rust (surface and corrosive)
Can Warped Brake Rotors Be Repaired?
In some cases, a warped brake rotor can be resurfaced rather than being replaced. When a car mechanic resurfaces a brake rotor, they return it to a smooth finish that provides the correct friction for proper braking.
Brake rotors that are resurfaced are not considered warped any longer because their surface is even again, but resurfacing a rotor does make the rotor thinner overall each time it is performed and decreases its remaining service life.
Brake rotors are commonly resurfaced any time the brake pads are replaced on a vehicle because putting new brake pads on an uneven brake rotor can drastically reduce the overall durability and life of the brake pad.
Once a brake rotor has been resurfaced several times in the course of changing brake pads, a mechanic will typically recommend to the driver that the rotors be replaced.
What Does it Cost to Have Warped Brake Rotors Replaced?
The cost of having warped brake rotors replaced can vary based on some of the following factors:
- State taxes
- Labor rates at individual shops
- Waste disposal fees
- Brake rotor material type
- Brake rotor condition
Brake rotors that are not too badly damaged can often just be resurfaced or repaired, which can be significantly cheaper than having the rotors replaced entirely.
On the flip side of that, brake rotors that have been allowed to be badly damaged due to continued neglect are more likely to have caused ancillary damage to the brake calipers and brake pads, which will drive up the cost of the overall brake repair job.
On average, the cost of replacing warped brake rotors ranges between $406 and $559, including the cost of mechanical labor.
Can You Replace Warped Brake Rotors Yourself?
Many repairs on a car can be undertaken by the car’s operator as long as they have some fundamental knowledge about how the car’s systems work and what parts/tools are needed for the job.
However, because the brake system is a serious safety concern when it comes to a car’s operation, the repair of the brakes should not be undertaken unless the driver is very experienced with car repairs. If a driver has never changed their oil before, they certainly shouldn’t be trying to replace their brake rotors off a YouTube video or something similar.
This is because failure to reintegrate the braking system correctly can lead to the brakes failing, and on the road this can have deadly lasting consequences or at the very least, wreck your car.
When in doubt, it’s always better to let a professional mechanic handle any repairs on your car that involve systems that involve passenger and road safety. Everyone has to start somewhere, but warped rotors might lead to other problems in the braking system that a novice mechanic may not recognize.
How to Tell if Your Brake Rotors Are Warped
There are several symptoms a driver might notice if their brake rotors are beginning to warp. Drivers should watch out for the following signs of warping brake rotors while driving:
- Noticeable vibration in the brake pedal (also known as brake judder)
- Noticeable vibration in the steering wheel
- Noises while braking such as thumping, groaning, and squealing
- Noted loss of performance in braking/stopping power
- Temporary loss of brakes
Because there is usually significant damage done to the braking system by the time some of these symptoms are noticed, it is important to have vehicles inspected regularly so that any wear and tear in these systems can be noted and addressed before it becomes a performance issue.
Not only is this the safest way to ensure that a car continues to brake correctly, it can also save in costly repairs to other components of the braking system down the line.
How Warped Brake Rotors Affect Your Driving
The most noticeable difference in the way warped brake rotors affect driving is that they increase the amount of time it takes for the brakes to stop a vehicle. This lack of stopping power can come on gradually or all at once, depending on how the rotors are warped.
In practical scenarios, this can lead to a driver misjudging the amount of space needed to brake at a light (causing them to plow into the vehicle stopped in front of them),
Warped brake rotors can also lead to the brakes failing entirely, especially during an emergency stop. This can lead to collisions or worse if the brakes fail while a driver is trying to avoid a street-crossing pedestrian.
How to Prevent Brake Rotors from Warping
The main thing a driver can do to prevent brake rotor warping is to not brake at excessive speeds or directly after accelerating.
Instead, a driver should take their foot off the gas pedal and allow the car to decelerate naturally before braking with an even, a smooth push of the brake pedal rather than stomping it to the floor.
By braking smoothly and coasting to a slower speed before applying the brakes, you can not only prevent warping of your brake rotors, but you can also increase the durability of your brake pads. A few simple changes to the way someone drives can greatly increase the life of their brakes.
Should All Brake Rotors Be Replaced at Once?
If it turns out that a car needs brake rotor replacement, it can often be an expensive investment. Brake rotors rarely need to be replaced (only above every third or fourth brake pad change, which means rotors usually only need to be replaced roughly every 200,000 miles).
That means if brake rotors do need replacing, there has usually already been some kind of damage done to the pads and calipers. Replacing the pads, rotors, and calipers on a car can range upwards of a thousand dollars.
Because front braking action is typically more important than rear braking action, for those on a limited budget, it is possible to replace the front brake rotors first and then get the rear brake rotors replaced at a later date.
‘This will increase the safety and stopping ability of the vehicle but will still give the driver a break on the expense involved.
Replace Brake Pads Regularly to Avoid Replacing Rotors
One of the most important ways to prevent premature brake rotor failure is to replace your brake pads regularly. This should be performed approximately every 50,000 miles, but some high-performance brake pads are designed to go as long as 70,000 miles.
Along with regularly inspecting your brake pads for signs of wear, you should also have your vehicle inspected on schedule by a mechanic, whether it needs repairs or not. An optimal time to do this is during a routine oil change at the repair garage.
Many car mechanics offer “trip checks” and other general inspections that will check out the systems on a car that may be needing maintenance attention, but you can also ask your mechanic to inspect the brakes specifically if you feel like your brake pads are starting to wear.
Unlike rotors, brake pads are often designed with a built-in “squealer” that causes the brakes to start squealing when they are within a thousand miles of seriously needing replacement. This gives a driver time to arrange for a stop at the garage.
Careful Driving Leads to Long-Lasting Brakes
Replacing warped brake rotors can be a hassle since it is costly and can be a repair that takes several hours, but this problem with the braking system of a car can be easily avoided with regular maintenance and careful driving. By allowing a car to glide at a slower speed before braking and being gentle when pressing the brake pedal rather than slamming the brakes or braking at excessive speeds, drivers can do their part to make sure brake rotors last as long as possible.
