Is rust on brake discs bad?

Rust on brake discs is a common issue that many car owners face. While surface rust may not cause any major problems, excessive rust buildup can definitely impact brake performance and safety. In this article, we’ll discuss what causes rust on brake discs, the potential risks, and how to prevent and remove rust.

What Causes Rust on Brake Discs?

There are a few key factors that contribute to rust formation on brake discs:

• Exposure to moisture – Brake discs are exposed to water and humidity from the road, car washes, rain, etc. Water promotes rust formation when it comes into contact with the iron in the brake disc.
• Lack of use – Brake discs that sit for prolonged periods without being used are more susceptible to rust. The braking action helps remove rust buildup from the surface of the disc.
• Long term parking – Vehicles left sitting outside and unused for weeks or months tend to develop more severe rust on rotors and other components.
• Low quality materials – Cheaper brake discs made with lower grade materials often rust faster than high performance discs.
• Salt exposure – Road salts used in winter weather can accelerate corrosion and rusting of brake discs and other braking system parts.

Is Rust on Brake Discs Dangerous?

Light surface rust on brake discs may not pose any immediate issues. However, excessive rust buildup can create a few potential hazards:

• Reduced braking power – Thick layers of rust act as an insulator, preventing the brake pads from making full contact with the rotor surface. This reduces friction and braking performance.
• Brake noises/vibrations – Rust buildup causes an uneven braking surface, which can lead to squealing, grinding or pulsing sensations when applying the brakes.
• Rotor cracks – Over time, rust can penetrate deep into the iron rotor material causing weak spots and cracks to form.
• Brake failure – In extreme cases with severe rusting, the buildup can detach from the disc surface causing complete brake failure. This poses an obvious safety risk.

So while mild surface rust only causes minor issues, extensive rust corrosion can make your brakes noisy, less effective and unsafe. It’s best to address rust buildup promptly before it gets out of hand.

How to Prevent Rust on Brake Discs

Here are some tips to help avoid rusting on your brake discs:

• Regular driving – Frequently using your brakes helps clean off rust from the discs.
• Wash regularly – Rinse road salts and grime off the undercarriage to limit rust catalysts.
• Coat rotors – Applying high temp brake disc sealant creates a protective barrier.
• Quality parts – Buy premium, long-lasting rotors to avoid premature rusting.
• Garage storage – Park your vehicle inside a garage to protect from moisture.
• Wheel rotation – Regular tire rotations better distribute brake use to all wheels.

While you can’t fully prevent rust on brake discs, good maintenance practices can significantly slow the rusting process.

How to Remove Rust from Brake Discs

If you already have excessive brake disc rust, here are some DIY cleaning options:

Sanding

Using 80-100 grit sandpaper, you can sand away rust layers and restore a smooth rotor surface. This is most effective for minor surface rust. Take care not to excessively thin the rotor by sanding too aggressively.

Wire brushing

A handheld wire brush or rotor resurfacing tool with built-in brush can scrub away stubborn rust. Wire brushing works well for lightly rusted areas.

Brake cleaner spray

Specialized brake cleaner fluid or aerosol spray works well to dissolve rust and grease from brake components. Be sure to avoid brake cleaner getting on any rubber or plastic parts.

Baking soda and vinegar

As a home remedy, you can scrub rotors with a paste of baking soda and vinegar. Rinse thoroughly after letting the paste sit for 5-10 minutes. The acidic vinegar reacts with the rust to help break it down.

Replace rotors

In cases of extreme rusting where rotors are deeply corroded, replacement is the only sure fix. Machining can refinish moderate rust, but won’t help if rust penetrates deep into the iron.

Do Brake Pads Wear Faster with Rusted Rotors?

Rusted brake discs can accelerate wearing of brake pads for a few reasons:

• The pads have to work harder and apply more pressure to generate braking friction against rust-coated rotors.
• Grit and rust particles act as abrasives that grind against the pad material.
• The uneven rust buildup causes vibrations that erode pads faster.
• Rust and debris get embedded in the pad material, reducing braking effectiveness.

So badly rusted rotors will typically shorten the lifespan of your brake pads. This is another reason to address rotor rust problems promptly through cleaning or replacement.

How Often Should Brake Rotors be Replaced?

There is no set mileage or time interval for replacing brake rotors. Factors that impact replacement frequency include:

• Vehicle use – Cars driven frequently or aggressively need rotors replaced more often.
• Mileage – High-mileage vehicles generally require more frequent rotor replacements.
• Climate – Rotors corrode faster in cold winter climates that use salt on roads.
• Driving habits – Aggressive braking wears rotors faster.
• Quality – Low-grade economy rotors rust and wear out quicker.

Many brake experts recommend inspecting rotors at each brake pad change. If the rotors are heavily rusted, deeply grooved or under the minimum thickness, replacement is advised. Quality rotors may last through two or more brake pad changes before needing replacement.

Can Brake Rotors be Machined to Remove Rust?

Yes, rotor machining using a brake lathe is an effective way to resurface rotors that have light to moderate rust. The machining process involves the following steps:

1. The rotor is mounted on the brake lathe.
2. The cutting tool smoothly machines away a thin layer from the surface of the rotor to expose fresh iron underneath.
3. This removes any rust, warping, and imperfections to create a flat, smooth finish.
4. Rotors must be machined within specifications to avoid excess thinning.

Brake machining has limitations though. It only works for surface rust and won’t help if corrosion has penetrated deep into the rotor’s iron structure. The rotor must also meet minimum thickness specifications after machining.

Can I Drive with Rusted Brake Discs?

You can drive with lightly rusted brake discs in the short term. But it’s crucial to have severely rusted rotors inspected and repaired promptly. Here are some guidelines on driveability:

• Minor surface rust – Acceptable for short term driving but clean off rust buildup as soon as possible.
• Moderate rust with light pitting – Have brake system inspected. Okay for short drives to repair shop.
• Severe rusting with deep pitting/flaking – Unsafe for driving. Have vehicle towed to shop for brake repairs.
• Penetrated rust causing cracks – Extremely unsafe. Do not drive the vehicle.

Be very cautious driving a vehicle with known rotor rust problems. Stop immediately if you smell burning brakes or experience odd brake pedal sensations.

Brake Rotor Rust Prevalence by Vehicle Make

Some vehicle makes tend to have more issues with premature brake rotor rust than others. Here are a few makes that tend to develop rotor rust problems faster:

Vehicle Make	Rotor Rust Tendency
Ford	Frequent
General Motors	Common
Chrysler	Very common
Toyota	Occasional
Honda	Rare

Domestic makes often use less expensive economy rotors prone to rust. Japanese brands tend to utilize higher quality, rust-resistant rotors. However, any vehicle can develop rotor rust if not properly maintained.

Common Causes of Premature Brake Rotor Rust

A few factors typically contribute to premature or excessive rusting of brake rotors:

• Prolonged vehicle storage – Sitting unused allows rust to take hold.
• Cheap rotors – Low-grade economy rotors rust faster.
• Winter climates – Road salts used in snowy regions accelerate corrosion.
• Infrequent driving – Brakes don’t get hot enough to burn off rust buildup.
• Aggressive pads – Performance pads lacking rust inhibitors promote rotor rust.
• Severe duty use – Demanding conditions like towing overload the brakes.

Being aware of these factors allows you to take preventative action where possible. For instance, storing your car in a garage, using high quality parts, and regular brake pad cleaning can all help minimize premature rotor rust.

Conclusion

While surface rust on brake rotors is mostly an aesthetic nuisance, extensive rust buildup can seriously impair brake system safety and performance. Catching and addressing rust issues early is crucial before they escalate into a more serious problem. With vigilant preventative maintenance and prompt repairs when needed, you can keep your brake rotors rust-free and your vehicle safe on the road.