Brake Performance Blogs

New hub units may exhibit rough feel when rotated by hand, a characteristic common with today's high performance products. SKF reports the rough or coarse feel of some new hub units if they are rotated by hand before installation and explains why these conditions are normal for technicians to experience.

In recent years there have been concerns about new hub bearings being rough or difficult to rotate. Many technicians inspect a new replacement hub bearing visually and by rotating the assembly once or twice by hand.

During the inspection process, it is not abnormal to feel a rough, coarse sensation as the two halves of the hub are rotated. This condition is not an indication of a defective bearing; these hub units should not be returned as suspected defective parts.

This condition is caused by the premium grease SKF uses in many of its bearings, especially in hub bearings. SKF uses GHG grease that provides a significant advantage over other standard greases.

SKF GHG contains many performance-enhancing additives, some of which are in the form of soft crystalline structures when the grease is new. These crystalline structures can create a rough, coarse feeling when the hub bearing is first turned by hand, before the bearing has experienced significant rotation.

These additives are important to optimum wheel bearing performance and include anti-brinelling and extreme pressure performance enhancers and solid lubricant components. This advanced technology grease chemistry improves bearing performance from many aspects, ranging from protecting against bearing damage during vehicle transport to maintaining proper lubrication conditions during high load/low speed operation to lubricant stability at elevated operating temperatures.

Even though the bearing may feel rough when it is initially rotated by hand, after rotating on the vehicle for a few minutes, the soft crystalline structures in the grease will break down into finer structures, and the bearing will rotate smoothly. There is no detrimental effect of the SKF GHG grease run-in. This is the normal and desired behavior of this type of grease.

Another item that may contribute to a hard turning hub bearing is the seal. In some hub bearings, the seals also have more interference with the bearing. Once the bearing is rotated for a few minutes, the bearing will gradually turn freely. This is a normal situation.

As a reminder, Generation 3 hub assemblies need to be fully preloaded/seated with the correct torque in order to operate properly. Without the proper bearing seating on a hub assembly, the bearing may have a feeling of roughness when turning it. The rough feel is more noticeable in bearings that are preloaded from the factory, as many of these newer generation hub units are preloaded. Always remember to follow the OE manufacturer's recommended torque specifications and procedures when installing the axle nut. This will create the correct preload for the hub assembly.

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.

When you step on your brake pedal, it forces the small piston(s) inside your brake caliper to compress, squeezing your brake rotors and essentially slowing down your car. Although this is the simplest way to explain the concept, it doesn't factor in some of the details that allow this to happen. Because the brake pedal doesn't just magically connect to all four brake rotors, it relies on the use of brake lines to divert your single force acting on the brake pedal onto the four corners of the car. These lines are filled with a hydraulic fluid we call brake fluid.

Brake fluid works well because it's a non-compressible, hygroscopic fluid which allows all the energy that your foot releases onto your brake pedal to be converted into braking pressure that squeezes your brake rotors and slows them down. So why is brake fluid so vital, yet often overlooked when shopping for brake rotors?

When you apply your brakes it causes your brake pistons to compress and clamp the brake rotors. This friction creates heat, lots of it. This means your brake fluid needs to retain its incompressible nature without boiling or evaporating due to the temperature.

What happens when your brake fluid boils or overheats? It creates air bubbles in the system and air is compressible opposed to brake fluid. So in turn, when you press down on the brake pedal, instead of clamping the rotors and slowing down the car, the brake fluid compresses the air and the brakes are not doing their job. This also translates to the driver as a mushy or unresponsive feeling brake pedal.

Brake fluid is a hygroscopic fluid that starts absorbing water, making it less effective. We suggest flushing your brake fluid once a year, but it's also a good idea to bleed your fluid every 6 months if you do a lot of hard braking. Hard braking on the brake rotors accumulates a lot of heat in the brake system and "boils" the fluid, creating air bubbles. Bleeding your brake system helps get rid of those air bubbles in the system.

For both bleeding and flushing your brakes, it's recommended to have fresh brake fluid readily available. If the fluid in the reservoir runs low while bleeding/flushing, it will induce air into the system, rendering the entire process useless.

Make sure the brake fluid is fresh and hasn't been sitting on the shelf more than 2 weeks if the seal has been opened. This is important as opened brake fluid is going to contain moisture. Unlike other brake components such as brake rotors or brake pads, brake fluid is sensitive to shelf life, especially when opened.

Always wear safety glasses and use proper equipment. Use common sense and take precautions as BrakePerformance does not take responsibility for erratic driving, accidents, damages done, or personal injury.

1. On a level surface, set the car in gear and place a stop behind the tires to keep it from rolling.

2. Open the hood and locate the master cylinder. This is where the brake fluid is filled from. Open the master cylinder cap (brake fluid reservoir) and place an old rag around it as you may get some spillage. (Do not drip on the paint of the car as brake fluid will etch.)

3. Using a turkey baster, suck out all the fluid. Most likely 20% will remain and that's okay.

4. Refill the reservoir back up to the fill line using fresh brake fluid.

5. Check with your manufacturer and find out the order in which brake calipers should be bled first. Normally, it's always starting with the furthest brake caliper from the brake reservoir. For example, if your reservoir is located in the engine bay by the driver side, you would start with the rear passenger brake caliper, rear driver brake caliper, front passenger brake caliper, and then finally the driver side brake caliper. This is just a general example; make sure to verify with your manufacturer.

6. Once you figure out the order, you want to jack up that side of the car and remove the wheel to access the caliper that you are about to bleed.

7. Secure the car by using jack stands once you jack up the car and remove the wheel.

8. Locate the bleeder valve. It helps to attach a rubber hose over it so the brake fluid doesn't drip everywhere.

9. Using an assistant, have him/her pump the brakes about 4-5 times, and they should notice it get stiffer. While they are holding the brake pedal down, open up the bleeder valve and fluid will come out. The trick is that you want your assistant to notify you to close the valve right before they hit the bottom of the brake pedal.

10. Repeat this process until fresh brake fluid comes out. Usually, old fluid is darker, and you will notice the shift to a lighter fluid indicating the fresh fluid has filled that brake line.

11. Repeat the same process for the remainder of the brake calipers and make sure that the brake fluid never gets below the minimum marker on the master cylinder. If this happens, you risk getting air into the system again and having to redo the entire process.

12. Once all four corners are done, top off the fluid in the reservoir to the max line, torque the wheel bolts to the proper specification, and verify you have a solid brake pedal feel before driving.

Bleeding Brakes

The process of bleeding brakes is identical. The only difference is that when you are bleeding each individual brake caliper, you only need to open the bleeder valve once or twice until you don't see any air bubbles come out. You do not need to wait until you start seeing fresh fluid. It is still necessary to have fresh fluid as it may drain most of what's in the master cylinder.

Brake fluid is a hydraulic fluid used in your brake lines. It takes the force your foot exerts onto the brake pedal and transfers it into braking pressure that then clamps your brake rotors, effectively slowing your car down. We use brake fluid due to its hygroscopic nature and its ability to resist compression. Essentially, you transmit all your force from the pedal to the brake rotor without losing energy due to fluid compression.

Now, because the brake rotors and brake calipers exert a high amount of heat, brake fluid must have a high heat tolerance. Otherwise, it would simply vaporize inside your brake lines and negate the purpose of the brake fluid. This is dangerous and results in your brake system not functioning properly.

Boiling Point is the maximum temperature before your fluid starts to boil. To further complicate things, there is a Dry Boiling Point and a Wet Boiling Point. Wet simply means the boiling point of a fluid after it has absorbed a certain percentage of moisture* (remember, it's hygroscopic). Dry is fresh fluid from a canister that hasn't been opened.

Below, we have the quality standards for each of the fluid classes:

• DOT 3 205°C/401°F (Dry) 140°C/284°F (Wet)
• DOT 4 230°C/446°F (Dry) 155°C/311°F (Wet)
• DOT 5** 260°C/500°F (Dry) 180°C/356°F (Wet)
• DOT 5.1 270°C/518°F (Dry) 190°C/374°F (Wet)

It's always recommended to only stick with the DOT rating your car recommends.

Using a DOT rating other than what is recommended may cause improper brake operation or premature failure.

*Wet boiling point is defined as 3.7% water by volume.

**DOT 5 is a synthetic non-hygroscopic fluid and should only be used for designated cars that support DOT 5.

With all this talk about brake rotors, we haven't forgotten about those of us that still use brake drums! Depending on your vehicle make and year, you could have all four drum brakes, or it's also possible to have a combination of rotors and brakes (i.e. Rotors in the front, brake drums in the rear).

The drum brake is made up of a few components. The brake drum is what you will see on the outside, which houses the internal components. The brake shoe, parking brake, and adjusting mechanism are what makes up most of what's hidden behind the brake drum.

Most of the time, you will be replacing the brake drum and the brake shoes. Those are the two brake components that see the most day-to-day wear. The parking brake (if it's integrated into the rear brake drum) also needs to be replaced normally around 75,000 miles, but earlier if you use it frequently.

Lastly, the adjusting mechanism which generally consists of the cable, adjusting lever, star wheel adjuster, and automatic adjuster spring can also see wear with age. This is more prevalent in harsh weather conditions such as rain and snow. If you are driving a vehicle 10 years or older, it's recommended to change it out regardless due to age.

To inspect the brake shoes, most drum brakes have an inspection hole where you can see the brake shoe friction surface to give you an idea of how much life is left. The minimum wear thickness should be:

• Un-bonded: 0.8mm or 1/32 inch
• Bonded to backing plate: 1.6mm or 1/16 inch

Uneven and scoured brake wear also indicates that the brake shoes should be replaced

Adjusting Parking Brake
Follow your manufacturers instructions as these are general guidelines and not a complete how-to. Because of the wide variety of different e-brake setups, use this as a guide, and not a comprehensive step-by-step instructional.
It's recommended to change your e-brake at 75,000 miles or at least adjust it every 2 years, depending on how often you use it. If your e-brake feels loose, it's usually the wires that simply need to be re-adjusted.

Adjusting Parking Brake

Most mechanical e-brakes are activated using thin steel cables that run from your e-brake handle, down to your brake mechanism. Over time, these cables develop slack and need to be re-adjusted. This is as simple as removing your center console or e-brake boot and locating the steel cables. Most of the time, it's a pair of steel cables that connect to the rear rotors.

There are two parts to the process. One is the jam nut which secures and tightens the steel cables in place. You want to loosen the jam nut so the steel cable moves freely. Next, locate the adjusting mechanism that tightens and loosens the slack of the steel wires. Usually if your e-brake handle feels loose and doesn't feel like it's grabbing, you want to tighten it.

In other cases, the e-brake can feel like it's overtightened. This usually results in a very heavy e-brake handle that only allows 1-2 clicks before it's engaged. Usually you want around 3-4 clicks as the brake resistances ramps up with the amount of clicks. Check with the manufacturer for recommended e-brake clicks and adjust to that.

After it's adjusted to your specification, tighten the jam nut to secure the new adjustment in place.
Make sure to rotate the rear wheels in the air freely to ensure that the e-brake isn't binding with the rotors with the e-brake lever fully released. Also make sure that the e-brake is functioning correctly by applying the e-brake and making sure the brake is holding the vehicle properly.

When to replace parking brake

Cars with over 150,000 miles or older than 10 years usually need their parking brake shoes replaced. If your parking brake is not holding your vehicle properly, check with our selection of parking brake shoes.

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.

Just about every component that's part of the car's brake system is vital to the safety and performance of your vehicle. Along with making sure your brake rotors are properly wearing, your brake pads have enough pad life left, your brake fluid is not contaminated, now you also have to deal with ensuring that your brake lines are operating as they were designed to.

Not to worry, as we want to make sure you understand how your brake system works without having to be a professional automotive technician! In order to understand the role of the brake lines, let's quickly go over the overall layout and function of the brakes. This quick and dirty visualization leaves out a lot of detail for the purpose of understanding the place for brake lines.

When you press down on your brake pedal in your car, hydraulic fluid is being forced from that single pedal, to the master cylinder, and then to all four of your brakes. The master cylinder essentially takes the pressure of your foot on the pedal, and converts it into usable hydraulic pressure. This pressurized hydraulic fluid then travels down through brake lines to each of your four brake calipers. This same pressurized brake fluid then compresses the pistons inside your brake calipers, forcing your brake pads to squeeze together essentially slowing down your brake rotors.

So why is it essential to replace old brake lines? First, almost all of the factory brake lines are normally made out of rubber hoses. As we know, rubber becomes brittle and loses its inherent characteristics as it gets exposed to weather and age. Instead of pressurizing the piston inside the caliper, the brake lines will expand or crack. What does this mean? It means that all the energy your foot is exerting is not going into slowing the car down, but just expending the brake lines (think of a garden hose with the end capped off and the hose expanding).

Essentially, you are at risk of losing braking power or complete control of your brakes should any of the brake lines burst. It's important to inspect your brake lines during your routine inspections and every time you change your brake rotors or brake pads.

Lastly, there are also stainless steel braided brake lines, which offer a more consistent brake feel and much better longevity against bursting and cracking.

The beauty of modern cars is that they have a lot more technology built into them that allows the driver to be informed of what is happening with the car, at any given moment. One of the biggest benefits comes from knowing the status and condition of your brake system. This is important because the properly functioning brakes are the last thing that keeps you and your car safe in moments of sudden danger.

Enter brake sensors. Sure, they may not have always been your favorite feature of the car, and had a pesky habit of lighting up your dashboard on several occasions. But they did it for your safety. More importantly, that is the only thing they were designed for. The safety of knowing when your brakes are in need of maintenance before it's too late.

The traditional method of jacking up your car and removing your wheels one by one just to inspect your brake pads and brake rotors is tedious and not exactly convenient. Not every car is equipped with brake sensors, so to some this is still the only solution. For everyone else, this is the down and dirty on how brake sensors work.

The brake sensor is normally attached to the brake pad itself. Because brake rotors wear at a similar rate on the front two brake rotors, it's pretty common to only see one brake sensor. This is because if one side is wearing low, it's almost always the case that the other side is at the same wear thickness. The brake sensor itself is normally a wire that is encapsulated by a plastic compound. Once the compound wears down to what is considered a minimum wear level on the brake pads, the metal wire makes contact with the metal brake rotor, creating a light to display on the car's dash. This holds true for the rear brake pads and rotors, too.

Once your brake maintenance light triggers, you need to replace the brake sensor as they are only meant for one-time use. Re-using old brake sensors that have already been triggered will not work even with new pads as they will always show your brakes need replacement, even if you just replaced the brake pads.