Brake systems are among the most critical safety components that ensure a vehicle can stop safely. At the heart of this system lie the brake discs, which can wear out over time for various reasons and pose serious driving risks. In this article, we examine in detail why brake discs wear out, under what conditions they are damaged, and how to prevent these problems.
Why Do Brake Discs Wear Out?
Brake discs are one of the main components that slow the vehicle by creating friction with the brake pads. This friction naturally causes wear on the disc surface over time. However, certain conditions can accelerate this process or lead to unhealthy wear on the discs.
Common causes of brake disc wear
- Hard and sudden braking: High pressure during abrupt stops causes an increase in temperature and microscopic deformation on the disc surface.
- Improper brake pad usage: Low-quality or incompatible pads can quickly wear out or scratch the disc.
- Sudden contact with water: Washing the vehicle or entering puddles while the disc is hot can distort the disc structure and cause warping.
- Insufficient cooling: Stopping the vehicle right after prolonged braking causes an imbalance in heat distribution on the disc, leading to surface hardening and cracking.
- End of disc lifespan: Over time, the disc surface thins, becomes scratched, and may develop metal fatigue due to use.
When Should Brake Discs Be Replaced?
The lifespan of brake discs varies depending on your driving style, vehicle model, and pad-disc compatibility. However, there are clear signs that indicate when discs need to be replaced:
Signs that indicate it's time to replace the brake discs
- Disc thickness is below the minimum value: Every disc has a manufacturer-defined "minimum thickness" value. Discs below this threshold must be replaced.
Note: When replacing discs, always consider the "min. thickness" specified by the manufacturer.
- Vibration in the steering wheel or pedal during braking: The disc may be warped, which disrupts braking balance and causes vibrations.
- Visible cracks, grooves, rust, or deep scratches on the disc surface: These physical deformations directly affect brake performance.
- Significantly increased braking distance: If the disc surface is uneven, the pads cannot grip properly, increasing stopping distance.
- Persistent brake noise: Irregularities on the disc surface cause uneven contact with the pads, leading to metallic friction noises.
What Causes Brake Disc Warping?
Warped brake discs cause the steering wheel to vibrate or the brake pedal to pulsate during braking. Common causes of disc warping include:
- Sudden water contact on hot discs: Washing the car or entering water puddles while the vehicle is hot can cause structural damage due to rapid cooling.
- Uneven pressure on the disc surface: Using old pads with new discs can cause surface deterioration.
- Irregularities on the hub surface: Improper disc seating creates balance issues.
- Stopping the vehicle after prolonged hard braking: Heat buildup in one area can warp that part of the disc.
How to Recognize Brake Disc Vibration?
Brake disc vibration can be identified through the following signs
- The steering wheel shakes from side to side during braking,
- A pulsating sensation is felt in the foot when pressing the brake pedal,
- The vehicle's stopping distance increases,
- Vibrations become more noticeable during braking at consistent speeds.
If you encounter these signs, both the pads and the discs should be checked.
Why Do Brake Discs Wear Out Quickly?
Some drivers notice that their brake discs wear out again shortly after replacement. Possible reasons include:
- Use of low-quality or incompatible brake pads,
- Driving style involving frequent sudden and hard braking,
- Failure to clean the surface during disc replacement,
- Uneven hub surface,
- Incorrect break-in process for new discs.
Why Are Pads Replaced When Changing Brake Discs?
When a new disc is installed, old pads can leave marks and scratches on the new disc surface in a short time. Therefore:
- Old pads may damage the new disc due to surface mismatch,
- Micro welding may occur, damaging the disc surface,
- Braking performance decreases and disc lifespan shortens.
The rule is simple: A new disc should be paired with new pads.
How to Break In New Brake Discs and Pads?
To ensure proper performance, new discs and pads must undergo a break-in process:
- Accelerate the vehicle to 90–120 km/h and perform moderate braking,
- Repeat this 3–4 times to allow the pad and disc surfaces to match,
- Complete the deceleration without coming to a full stop, as remaining stationary can lead to micro welding.
This process helps evenly heat the disc surface and creates a smooth braking contact area.
How to Extend Brake Disc Lifespan?
To extend the life of your brake discs and prevent wear, consider the following tips:
- Do not wash the vehicle when the brake system is still hot,
- After a long drive, allow the brakes to cool by driving slowly for a few minutes instead of stopping immediately,
- Avoid driving quickly through puddles,
- Choose high-quality brake pads that match your vehicle,
- Have your brake system checked during every maintenance session.
What to Do If You Experience Issues with Brake Discs?
If you still feel vibrations after replacing the brake discs:
- Inspect the hub surface and check for unevenness,
- Examine for installation errors (e.g., incorrect torque on bolts),
- Tire balance can also affect brake vibrations—have it checked.
If needed, the system should be reassembled after completing all these inspections.
How is Brake Disc Thickness Measured?
Brake disc thickness is measured using a caliper or micrometer. Usually, the disc is marked with:
Min. Thickness: X mm
If the disc is below this value, it must be replaced. Otherwise, braking performance will be significantly compromised.
In conclusion, regular inspection and proper maintenance of brake discs are vital for both your safety and the smooth operation of your vehicle. It’s not just about whether the brakes work it’s about how well and evenly they perform, which is crucial for safety.
