Brake Performance Blogs

Brake rotors aren't exactly known to be the cleanest part of the car. In fact, the brake rotors often become these ugly little gremlins that you are forced to accept as part of your car. But the truth is not all brake rotors have to be hideous. There is a reason brake rotors develop rust and start looking like ancient archeological dig items after a few months, but that's not something we have to live with in today's age.

Rust build up on brake rotors is not only unsightly, but it's detrimental to the brake rotors structural integrity as well as performance. Excess rust starts to eat away at the brake rotor, creating a brake rotor that has varying thicknesses and is exposed to heat cycles. This doesn't sound like a big deal, but let's take a closer look at it. When metal heats up, it expands.

Conversely, metal also shrinks when it cools down. Now picture a brake rotor that is heating up and cooling down, with varying thickness. That means each part of the rotor is expanding and shrinking at a different pace than its adjacent counterpart. This occurs at every heat cycle and can lead to premature wear, cracks and balancing issues.

We make sure to coat our brake rotors in a zinc coating in house. Because we control the zinc process ourselves, we offer the choice of two finishes on the zinc treatment on any performance BrakePerformance Rotor: Bright Silver and Stealth Black. Although the treatment isn't a guarantee against rust, it surely does help more than using an untreated rotor. Best of all, you reduce the unsightly rust that forms!

With all the different types of brake rotors available, it's hard to keep up with the new features that are part of brake rotors.

Let's talk about dimpled rotors. Dimpled rotors are actually quite similar to the dimples on your face. No joke! The need for dimpled rotors arose because enthusiasts with heavier cars were looking for an improved rotor that had better cooling and brake pad outgassing properties than just a plain rotor.

What are dimpled rotors? Dimpled rotors are brake rotors that have a dimpled cavity. These indentations on the rotor's contact surface, round in nature, allow the brake pad to outgas properly. Its minimal depth doesn't affect the structural integrity of the rotor, thus it's also a great solution for heavier SUVs and trucks. As a matter of fact, heavier SUVs and trucks is one of the factors that stemmed the development of the dimpled rotor. The dimpled rotor is an evolution of the cross-drilled rotor designed for track and sport cars. Because SUVs and trucks exert a much higher load and stress on the brake rotors, the dimpled rotor is recommended due to the higher stress handling capacity.

Outgassing is important as it allows the brake pad to "breathe". This bit of extra breathing room is especially vital in situations of heavy load such as towing or instances of heavy brake use.

For lighter cars such as coupes and sedans, the cross-drilled rotors offer the same outgassing functions with a bit better cooling capacity.

The naked eye alone is usually not able to tell if a brake rotor is warped or not. There are a multitude of reasons why you may believe your brake rotors are warped. It's important to narrow down your symptoms so you don't end up replacing the wrong components and wasting money.

Brake Pedal Vibration

Probably the most common sign of a warped brake rotor is the vibration through the brake pedals when pressure is applied on them. Sometimes you can feel it even when there is only a light amount of pedal pressure on the brakes. Other times, it can only be felt when slowing down drastically from higher speeds.

Steering Wheel Vibration

The brake rotors and brake calipers are attached to the same spindle that the wheels are attached to, so in certain cases vibrations from warped brake rotors will transmit through the brake calipers and then to the wheels and steering wheel.

Brake Noise

There are certain cases where you will hear noises emitted from your brake rotors during braking. This is due to the brake rotors contacting your brake pads at uneven intervals due to the rotor no longer having a flat surface. These noises can range from a lower pitched groaning hum to a rhythmic thumping.

Malfunctioning Brake Calipers

With the brake calipers squeezing the rotors together, a malfunctioning brake caliper may exert too much force, putting too much stress on an overheated brake rotor causing it to go off-balance, leading to warped brake rotors.

Damaged Wheel Bearing

If your wheels are not bent, but there seems to be a wobble, it is most likely due to a worn-out wheel bearing that has excessive play. This can also lead to warped rotors and inconsistent brake pad wear, along with more serious issues. If a damaged wheel bearing is the culprit, it should be replaced or it will continue to be a source of warped rotors and uneven brake pad wear.

Months after a new installation of brake pads and brake rotors a pulsation in the pedal has slowly developed. There is very little wear, and there are no visual indicators of a problem. The brake pads are worn evenly, brake rotors look clean with no corrosion.

Measuring the lateral runout and disc thickness variation will give you a better idea of what is really happening. This runout can originate from improper brake hardware maintenance, corrosion and debris on the hub mounting flange, or even improperly tightening the lug nuts. The average maximum allowable runout is between 0.001" and 0.003" with some manufacturers specifying 0.000" of allowed runout. Runout can create thickness variations in the brake rotors which will lead to problems with uneven wear and pulsation. This type of problem is not to be confused with warping caused by heat distortion.

If a brake rotor has a high-spot of lateral runout, that point will circle past the calipers hundreds of times within just one mile, multiply this over thousands of miles, and that point will have scraped the brake pad millions of times. This seemingly small problem can cause enough of the rotor to be removed over time that a variation in thickness can be felt by the driver.

Brake rotors will not last forever, they wear down a little bit every time the brake pedal is applied. How fast the rotors wear depends on a lot of variables including the type of brake pads, quality of the materials, how fast the rotors cool down, driving style, exposure to moisture and road salt.

Most original equipment brake rotors used to be designed with enough thickness to last at least two or more pad replacements. Most newer cars have thinner rotors to save weight and could be worn to the minimum by the first time the brake pads need to be replaced. Normally both rotors need to be replaced because they will usually have the same amount of wear. Even if one side is "good enough" it is wise to replace both brake rotors at the same time to maintain even braking as any difference in rotor thickness will cause the brakes to pull to one side.

If a brake rotor has minimal lateral runout it should wear evenly, otherwise the result will be thickness fluctuations which will create vibration. It only takes .001 inches of thickness variation to cause a noticeable pedal vibration. Excessive runout can be solved by installing tapered shims between the brake rotor and hub, or by resurfacing the rotor with an on-car brake lathe. Runout can also be corrected using a conventional bench lathe, but it is a much more difficult procedure. Cleaning the face of the hub and the inside of the rotor hat with a drill powered brush before installation will remove dirt, rust, or any particles that can create gaps between the rotor and hub. Rotor distortions can be caused by improper tightening of the lug nuts. Uneven torque between lugs can twist the rotor hat, causing the disc section of the rotor to wobble.

Friction from the brake pads against the brake rotors generates a lot of heat. Overheating brakes will shorten the life of both the pads and rotors. Vehicles that spend most of their time in stop-and-go traffic, pulling a trailer, or mountain driving will wear out the brakes much sooner than vehicles which are driven mostly in light traffic. Hard spots and discoloration can also develop from excessive heat. These hard spots yield uneven wear across the brake disc. Trying to shave them off by resurfacing will not cure the problem because hard spots extend below the surface, the only fix is rotor replacement.

If your brake rotors have sufficient metal remaining with no hard spots, cracks, severe grooving or rusting, then the rotors could be resurfaced. Some have the opinion that unless the brake rotors have surface issues needing to be fixed, the rotors should not be resurfaced every time the pads are replaced. If the brake discs are still smooth they may not need to be resurfaced, but most professional brake mechanics will not install new brake pads without resurfacing the rotors. Resurfacing restores a flat and even surface that minimizes vibrations and allows for maximum brake pad friction. Installing new pads on a grooved brake rotor will not allow the pads to make full contact with the brake disc, and eventually the pads will wear down and fully seat themselves into the contours of the brake discs, but this will only decrease the life of the brake pads.

As inexpensive as rotors are now, it is affordable enough to simply replace the rotors rather than paying to resurface them. New brake rotors should be ready to install right out of the box. There is no need to resurface them as this may actually produce runout and will reduce their service life. If your vehicle originally included brake rotors with a separate hub and disc (composite rotors) they can safely be replaced with cast iron brake rotors. Cast rotors are more rigid than composite rotors, but they may slightly affect steering and handling on some vehicles. For those customers who are interested in increased brake performance and safety, we recommend premium brake rotors over the standard replacement brake rotors.

Anytime you install new brake rotors, brake pads, or both, it's advantageous to bed in your new brakes. Bedding in your brakes is just an industry term to explain breaking in your new brakes.  Bedding in your brakes helps transfer an even layer of brake pad material onto the brake rotor which assists in smoother brake operation and improved braking power.

Having a uniform layer of pad material on the brake rotor is essential to minimizing brake squeal and vibration. For this procedure, you will need a good stretch of road and no traffic.

Use common sense and take precaution as BrakePerformance does not take responsibility for erratic driving, accidents, or damages done.  

Note: When using Brake Performance Zinc-Coated rotors, as soon as you start braking, the friction from the pads will strip the zinc from the pad surface, turning it Silver and leaving the holes, slots, and the rest of the rotor zinc coated in the color you selected.

• Perform 3-4 medium stops from 45mph. Slightly more aggressive than normal braking. You don't need to come to a complete stop for each pass. This brings the brake rotors up to temperature so they are not exposed to sudden thermal shock.
•  Make 8-10 aggressive stops from 60mph down to 15mph. For this set of semi-stops, you want to be firm and aggressive, but not to the point where ABS activates and the wheels lock up. It's important to note that you don't come to a complete stop but rather a semi-stop (~15mph). Accelerate back up to 60mph as soon as you slowed down to your semi-stop.
• The brake pads and brake rotors are extremely hot at this point and sitting on one point will imprint the pad material onto the surface unevenly. This can cause vibration and uneven braking.
•  You may notice that your brakes will start fading, and sometimes smoke, after the 6th or 7th pass. This fade will stabilize and will gradually recess once your brakes have cooled down to normal operating temperatures. Drive carefully as your brakes may feel softer for the next few minutes.
• Try not to come to a complete stop and find a stretch of road where you can coast for 5-10 minutes, preferably without using your brakes.

After the break-in procedure, there may be a light blue tint on your brake rotors as well as a gray film deposit. The blue tint shows that your rotor has reached the appropriate temperature during the bedding process, and the gray film is some of the pad transfer material.

Some cars and trucks require two cycles of the bedding in procedure. This may be the case if you are using old brake rotors with new brake pads, or new brake rotors with old pads. This may also be the case if you don't think you fully heated up the brakes in the initial bedding procedure. In any case, it's required that you wait at least 10-15 minutes between each cycle as you don't want them to overlap.

It's important to measure your brake rotor wear every 10,000 miles or at the very least every time you change your brake pads. You want to use a micro measuring caliper to determine your brake rotor thickness. For example, a new brake rotor with a thickness of 10mm is required to be replaced or turned at 9mm, meaning that your naked eye has to detect 1mm of rotor wear. Kinda impossible.

In order to get an accurate measurement for the amount of brake rotor wear we depend on our trusty micrometer. Prepare your car so you can remove the wheel.

With the wheel removed, you will have clear access to the rotor for you to make accurate measurements. There are several types of micrometers and measuring calipers so you want to make sure your caliper can measure to the tenth of a millimeter.

Next, you simply measure the thickness in at least three different spots of the brake rotor. Make sure to write down your measurements and you may get a few small variations. It helps to get at least 4-5 different measurements and to take the average of that.

Next, take a look at the brake rotor center hat. This is the portion that doesn't get exposed to the brake pad. You will normally find your minimum rotor thickness stamped there. It may be faint, but it's usually there. In some cases it may be located on the outer edge of the rotor.

Tip: Keep in mind that you want to avoid measuring too close to the inside/outside of the rotor, as the actual brake pad doesn't contact those edges. Also, for slotted rotors stay away from measuring the slots, as those will skew the results. Same goes with dimpled/cross-drilled rotors. Keep clear of measuring the holes.

Measuring Rotor Thickness

It's impossible to tell how much life is left on the brake rotors by simply looking at it. As a matter of fact, it's dangerously misleading! By simply looking at brake rotors, most rotors seem to be wearing fine unless there are cracks or huge chunks missing.
However, that is where the huge misconception lies.
Unlike brake pads, which show how much pad is left and have warning sensors, brake rotors have no such indicators. It's important for the safety and performance of your car to inspect these properly. We recommend inspecting your brake rotors every 10,000 miles to make sure they are within specs.
Follow our visual guide on how to inspect your brake rotors in just 6 steps. Make sure your rotors are cool prior to inspecting.
Note: If you observe any one of these 6 symptoms, it's recommended that you replace your brake rotors.

1. Visible Cracks
One of the most obvious ways to check when your rotors need to be replaced is through visible cracks. If you see a crack, it's time to replace your rotor. However, in certain cases small hairline cracks are normal if you race your car, such as track days and timed performance events. Keep in mind if you don't know the difference, it's better to be safe than sorry.

2. Grooves
 If you have an open-spoke wheel design, you can run your finger vertically down the brake rotor friction surface. If you can feel and see noticeable grooves, then it's time for new brake rotors.
For cars with hub caps that don't expose the rotor, you will need to remove your wheel to inspect your brake rotors.

3. Rotor Edge Lip
On worn brake rotors, if you follow the rotor to the edge you can usually feel/see a noticeable lip. This lip is created as the brake pads normally don't contact all of the rotor surface and therefore leaves an outer lip when the rotors are worn down.
Keep in mind that rotors reach their wear limit at only about 1mm. If there is an obvious lip, it's most likely near its wear limit or is wearing unevenly. Measure with calipers to double-check.

4. Heat Spots
Heat spots (Fig. x) are a telltale sign that your brake rotors have uneven brake pad deposits. How do they affect you? Heat spots will lead to brake harshness, vibration, and reduced structural integrity. Heat spots on brake rotors occur when brakes aren't broken in (bedded) properly and the brake pad deposits on the rotor accumulate and eventually turn into a compound known as cementite. You don't want Cementite on your brake rotors. Cementite is a compound that is very hard, overly abrasive, and doesn't allow the rotors to cool properly. As a result, Cementite heats up the local area around itself growing in size and reducing the cooling capacity of your brake rotors.
Prevention: Properly breaking/bedding in your new brake rotors is vital to the longevity of the rotor. See our Brake Rotor Bedding Guide.
If this is caught early on, you can possibly remedy it by bedding in your brakes with a more abrasive pad, or resurfacing your rotors. If the heat spots are extensive, you will need to replace your rotors.

5. Rust
There are two types of rust that occur on brake rotors. Surface rust and corrosive rust. Most of the rust on brake rotors is known as "surface rust". Just like it sounds, imagine surface rust on brake rotors as a thin top layer of rust. This doesn't affect braking performance and most of it wipes off when you apply your brakes. Although some of it remains, such as on the hub and rotor vents, it doesn't hinder performance but it can be unsightly.  Our zinc and e-coated rotors aid in preventing such rotor rust from forming and tarnishing your beautiful brake rotors.
Corrosive rust on the other hand is the evil twin brother. This is the rust you see when you live in harsh conditions where road salt (electrolytes) is often used. You don't want this type of rust. This rust often happens when you neglect your car and let it sit for extended periods of time without driving, allowing the rust to etch into your rotors. This affects the structural integrity of your rotors as well as effectiveness. If this happens, we recommend replacing your rotors.
BP Coated Rotors are specifically coated with a zinc coating to protect against surface rust.

6. Warped Rotors
Although the term "warped" rotors is very commonly used, it's in fact one of the least common causes of brake vibration. In fact, what happens in almost every case of a warped rotor is simply uneven pad deposits or heat spots. Uneven pad deposits happen from using incorrect break-in procedures. Follow our break-in guide (also known as "bedding your pads") to prevent vibration and premature rotor and pad failure.

One of the most common questions we hear is: What’s the advantage of drilled and slotted brake rotors compared to stock (plain) OEM rotors? The answer comes down to improved stopping performance, better heat management, and longer-lasting braking consistency—especially under real-world driving conditions.

The Advantage of Slotted Rotors

Slotted brake rotors are designed to significantly improve braking performance. Each rotor is precision-machined with four to five slots per side (vehicle-specific), extending to the outer edge of the rotor. These slots serve several important purposes:

• Clear brake dust, water, and debris away from the pad surface, ensuring consistent pad contact
• Improve wet-weather braking by maintaining a clean friction surface
• Reduce brake fade by allowing heat to escape more efficiently
• Promote even pad wear and better pedal feel

Machined rotors deliver more responsive, confident braking, especially during repeated stops or aggressive driving.

What Do the Drilled Holes Do?

Another frequently asked question is about the purpose of drilled holes. Their primary function is heat dissipation. During prolonged or heavy braking, heat builds up between the brake pad and rotor. Drilled rotors allow this trapped heat to escape, helping to:

• Maintain consistent braking performance
• Reduce the risk of brake fade
• Extend rotor and pad life

Dimpled slotted vs. Cross-Drilled slotted Rotors

Performance rotors are available in different styles as listed in our performance brake rotors page but these two drilling styles, each designed for specific vehicle needs:

• Dimpled & slotted Rotors
  These feature shallow, non-through holes that dissipate heat without fully penetrating the rotor surface. This design maintains structural integrity, making them ideal for heavier vehicles or applications prone to rotor warping.
• Cross-Drilled & slotted Rotors
  Cross-drilled holes pass completely through the rotor, allowing air to flow through the disc for maximum cooling. This design is commonly used on light- to medium-duty vehicles and high-performance applications, where improved heat dissipation and reduced brake fade are critical.

A Worthwhile Upgrade

The noticeable improvement in braking performance, combined with enhanced cooling and cleaner operation, makes drilled and slotted brake rotors a smart upgrade over standard OEM replacement rotors. Backed by a manufacturer’s warranty and trusted by customers for over 20 years, our machined performance brake rotors deliver the stopping power, reliability, and value drivers expect.

With all the different types of rotors available today, it can be intimidating when you don't know which one fits your needs. We get multiple calls a day from customers asking if the slotted rotors are the right brake rotors for their needs. In short, there is nothing wrong with the way plain brake rotors function, as we assure that all of our rotors are made to meet and exceed the manufacturer's specs.

Let's get back on topic. As we all know, brakes are one of the most important components to your own safety and the car's safety as well. With every driver, there is a specific driving preference which is why there is such a variety of brake rotors available.

One of the most popular and versatile brake rotors would be our slotted rotors. Slotted rotors are brake rotors with slots etched onto the friction surface of the rotor. These slots help "wipe" the brake pad clean during each pass and help maintain even pad wear as well as performance. While even pad wear promotes longer brake pad life, the slots also help direct brake dust away from the face of the wheel, keeping your car cleaner as well as preventing severe debris build-up around your brake components.

Lastly, all BrakePerformance Slotted Rotors feature slots which extend all the way to the edge. This is especially helpful during wet driving conditions as the slots help direct water on the surface of the rotor away from the friction area, reducing wet braking distance.

Often viewed as performance rotors, slotted rotors offer benefits for everyone. Regardless if it's an SUV, or daily commuter, improved braking performance in all weather conditions and better brake pad life is a plus in anyone's book.