Buying guide for best brake rotors

When thinking about your car’s safety features, most of the attention these days is on high-tech solutions: backup cameras, lane monitoring systems, and automatic braking systems grab the headlines. But real hardware still exists behind the high-tech, like the brakes. It does your vehicle – and more importantly, the passengers – no good if the automatic braking sensors activate brake rotors that don't work properly.

Most people know they need to replace the brake pads regularly, but you might not know the parts of the brakes that the contact the brake pads – the brake rotors – also wear out over time and need replacing.

The first disc-style brakes appeared in race cars in Europe in the early 1950s and then in consumer vehicles in the U.S. and Europe throughout the 1950s and 1960s.

What are brake rotors?

Brake rotors are part of a motor vehicle’s braking system. The rotors are round metal discs that you might be able to see inside the tire of your vehicle, especially if you don’t have hubcaps. When you remove a tire, you can clearly see the brake rotor. Each wheel on your vehicle has one.

On most cars, the brake rotors are cast iron. High-performance vehicles might use brake rotors of reinforced carbon or ceramic composites to reduce weight.

The brake rotor is part of the wheel, which connects to the vehicle’s axle. As the axle rotates, the wheels rotate, propelling the vehicle forward. When you need to stop, the brake rotor and braking system come into play.

How does a braking system work?

The brake rotors are only part of the braking system that slows and stops your vehicle.

The braking system uses a caliper with two brake pads attached to it. Pressing the brake pedal pinches the ends of the caliper together. This action presses the brake pads against the brake rotors, creating friction.

Because the brake rotors are connected to the wheel system, this friction eventually stops the tire from spinning. When you release the brake pedal, the caliper ends flex back open, disengaging the friction between the pads and the rotors, and the wheel moves freely again.

Types of brake rotors

When selecting new brake rotors, you can pick from two primary types: drilled and slotted.

Drilled brake rotors have holes drilled through the rotor disc to allow the heat generated from the friction to dissipate more quickly. Excessive heat around the brake rotors and pads can cause the system to work less effectively.

The holes in the brake rotors also allow water to pass through. If you're driving on wet roads, the brake rotor could become slippery if it stays wet. The water dissipates more quickly when the rotor has holes.

However, rotors with holes have less surface area to generate friction between the rotor and the pads, which could cause the brakes to work more slowly. Also, if not drilled correctly, the holes could weaken the structure of the rotor. However, the benefits of holes in the brake rotors significantly outweigh the minor drawbacks.

Slotted brake rotors have thin slots or lines in the surface. These slots aren’t deep enough to weaken the brake rotor, but they are just the right depth to help remove water and heat.

You’ll find slotted brake rotors more often on high-performance vehicles where the rotors are under excessive stress. Holes in the rotors could cause a brake system failure in this type of vehicle. Most consumer vehicles don’t put excessive stress on the rotors, so slotted brake rotors aren’t necessary.

One disadvantage of slotted brake rotors is that the brake pads tend to wear out faster versus pads on drilled brake rotors. Also, on average, slotted brake rotors are more expensive than drilled rotors.

How do I know if my brake rotors need replacing?

You often can’t tell if the brake rotors have too much wear just by looking at them. However, there are clear signs you can follow when trying to decide whether you should replace the rotors.

Measure the wear. You can measure the wear on brake rotors using a micrometer. This type of caliper will tell you the exact thickness of the material to a fraction of a millimeter.

Take four to six measurements around the rotor. Always measure in a location where the brake pads have touched the rotor.

The original thickness of the rotor should be listed in the vehicle’s user manual. If the brake rotor has worn down beyond acceptable limits or if the wear is uneven, it will need to be replaced.

Listen for odd noises. If your brakes make loud whining or squealing noises, this often is a sign of a failing brake pad. However, it also could signal a brake rotor problem.

Sometimes this high-pitched noise is caused by metal on metal – the brake pad has been completely worn down. This problem will eventually cause the brake rotor to fail. The rotor needs a functioning brake pad in order to work.

A poor-quality or worn brake pad also can cause grooves to appear in the surface of the rotor, which can sometimes cause a high-pitched noise. If the grooves become deep enough, the rotor must be replaced.

Notice any vibrations. If your vehicle shakes when you apply the brakes, this points to a warped brake rotor or an underinflated or weakening tire.

If the rotor is causing the vibration, it means the rotor has suffered wear on some part of the surface and is no longer of a uniform thickness.

Brake rotor prices

Once you’ve determined that you need new brake rotors, you have two options: you can pay a mechanic to do it, or you can do the installation work yourself.

Mechanic

Almost any mechanic or repair shop can do this job in a short amount of time. Most mechanics will recommend replacing at least two brakes (on the front or rear wheels) at the same time.

• Complete brake system: If you need a complete brake system replacement, including the pads, caliper, and rotors, you can expect to pay between $350 and $700 per wheel. (Remember, each wheel has its own brake system.) Labor costs account for about 50% to 70% of the total bill.
• Rotor replacement: If you’re only having the brake rotors replaced, it will cost about $150 to $300 per wheel. Again, labor is a significant percentage of the cost. However, understand that if the rotors must be replaced, most mechanics will recommend replacing the entire brake system.
• Rotor and pad replacement: At the very least, most mechanics will recommend replacing the pads and rotors at the same time. This will run about $200 to $400 per wheel. Some mechanics will refuse to just change the rotors alone.
   

Doing it yourself

Choosing the DIY option will certainly save you quite a bit of money. However, replacing rotors requires some auto repair know-how, as well as some specialized tools. Purchasing tools or renting space at a DIY garage will drive up the cost of doing the repair yourself. Before deciding to replace the brake rotors, think about all the potential costs you’ll encounter.

• Brake rotors: Considering the high price of having a mechanic work on your braking system, the actual cost of brake rotors is relatively low. Before buying any type of brake rotor, make absolutely sure it’s compatible with your vehicle’s make and model. The hub attached to the rotor will be of a different size and thickness depending on the vehicle.
   

Average-quality brake rotors cost anywhere from $25 to $60 each. These are basic models made for lightweight vehicles.

High-end rotors cost $200 to $250 each. The more expensive brake rotors are made of better quality materials or are specialty rotors for certain vehicles.

You will find disc brake systems using brake rotors on extremely large vehicles, including some airplanes and railroad cars. It’s a time-tested braking design.

FAQ

Q. How long should brake rotors last before needing replacement?

A. The longevity of brake rotors varies greatly from vehicle to vehicle. If your car uses especially rough or aggressive brake pads, the rotors will wear down more quickly. If your vehicle’s manufacturer used low-quality materials to make the brake rotors, such as poor-quality cast iron, these rotors will wear more quickly. On average, brake rotors last for 30,000 to 75,000 miles, but some high-quality rotors can last even longer.

Q. Can I change out my own brake rotors?

A. Some people can swap out their brake rotors themselves, while others will hire a mechanic. You need to be able to safely jack up the vehicle. You need to know how to remove brake fluid. You have to remove several large bolts, so you’ll need the right tools on hand. This is an intermediate-level DIY job, so you’ll have better success if you already have some experience working on vehicles.

Q. How long does it take to swap out the brake rotors?

A. When changing your vehicle’s brake rotors, you will probably also change the brake pads. For an experienced mechanic, the process can take between half an hour to one and one-half hours for two wheels. If you haven’t worked on vehicles a lot, the process could take up to three hours for two wheels. Novices might need three to five hours for two wheels, especially if they don’t have the proper tools.