What Is That Black Build-Up on Your Car Wheels?

Have you ever looked at your car and noticed a black substance on your car wheels? Do you know what that substance is? It’s called brake dust. While it mostly doesn’t feel like dust, it is normal in small amounts but can be worrisome in large quantities.

Where does brake dust come from that ends up on your car wheels?

Brake Dust on a Car Wheel
Brake Dust on a Car Wheel | Shutterstock

Modern cars use disc brakes which include rotors, calipers, and brake pads. When you depress the brake pedal, the calipers squeeze the pads to the rotors, slowing or stopping your vehicle. The brake pads are made from compressed steel fibers and additives. These materials wear over time and are expelled from the braking system as the dust and dirt you see on your car wheels.

In short, brake dust is a mixture of metal shavings from the rotor and dust from the pad.

Is it normal to have brake dust on your car wheels?

Yes, a small amount of this black build-up is normal, but if it becomes excessive, you might need to worry. If you don’t clean your wheels regularly, at least whenever you wash your car, you won’t truly know if you have an excess problem or simply haven’t washed the wheels as often as you should.

In some cases, you could experience excessive dust from the brakes. This can happen when:

  • You use dusty pads – typically the case with cheap brake pads
  • You could have a sticky brake caliper – this is a real problem
  • There could be a scored brake rotor present – this means an uneven rotor surface

Why are my front wheels always dirty?

Rust-Colored Brake Dust on a Wheel
Rust-Colored Brake Dust on a Wheel | Shutterstock

In most vehicles, the braking process happens mostly at the front wheels. Rear brakes aren’t engaged as often unless you have a vehicle with AWD. Because the action happens in the front, more brake dust appears on the front wheels than on the rear. You might see some cars on the road with nearly black or gray wheels up front while the rear wheels remain shiny and clean.

What causes excessive brake dust?

A Rusty Brake Rotor and Frozen Caliper Could Cause Excess Brake Dust
Rusty Brake Rotor | Shutterstock

Typically, you won’t see excessive brake dust on both wheels of your car. According to Torque News, when the excess appears, it’s usually only at one wheel, and it could indicate a brake caliper that has frozen. This means the caliper helps slow your vehicle down but doesn’t release the rotor when you take your foot off the brake pedal. This can lead to a few issues, including:

  • A bad brake caliper that needs replacing
  • Worn down brake pads and rotor
  • Lowered fuel mileage
  • Excessive tread wear for your tires

Do you need to clean the brake dust from your car wheels?

Wheel Cleaner to Remove Brake Dust
Wheel Cleaner to Remove Brake Dust | Shutterstock

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Brake dust is harmful to your car’s wheels and paint. It can eat through the clear coat and damage your wheels and potentially the body of your car. Remember what this material is made of; metal shavings and additives, none of which is good for your vehicle or the rims you enjoy when they are clean.

The best way to remove brake dust from your car wheels is with a wheel cleaner. This is an easy-to-use product that only takes a little time to bring your wheels back to the clean look you want to see.

Now that you know about brake dust, continue to the next article to read about some things you need to stop doing with your car.