Brake Noise at Low Speed

Brake noise at low speed, often described as a squeaking or grinding sound, is usually caused by one of three common issues: brake dust accumulation, worn brake pads, or moisture on the rotors.

1. Brake dust buildup: Over time, dust from the brake pads can gather between the pad and rotor, causing a high-pitched squeal. Cleaning the brakes with a specialist cleaner often resolves this.
2. Worn brake pads: Most pads have wear indicators that create noise when the material is low. If ignored, this can lead to rotor damage. Check pad thickness—if below 3mm, replace them.
3. Moisture or corrosion: Damp conditions can cause a thin layer of rust on rotors overnight, leading to temporary noise. Gentle braking usually clears this.

If the noise persists, have a mechanic inspect the calipers or rotor alignment. Some performance brakes (e.g., BMW M Sport setups) naturally produce more noise due to harder pad compounds, but excessive grinding suggests urgent attention is needed.

From a mechanic’s perspective, low-speed brake noise often signals minor issues needing quick fixes. A quick inspection can identify if it’s just surface rust (common after rain) or a loose shim behind the pad. For performance cars like the Audi S3, semi-metallic pads may squeak more than ceramic ones. If the noise disappears after a few stops, it’s likely harmless. Persistent grinding? That’s pad wear or rotor scoring—book a service.

The causes of brake noise when a car is driving at low speed include brake pad break-in, sand particles entering, brake system malfunction, severe brake disc wear, and ABS system activation.

The reasons for brake noise during low-speed driving are as follows:

1. Brake pad break-in: The break-in of brake pads is a crucial part of the running-in process for new cars. It usually takes a few hundred kilometers before the brakes feel smoother. Newly replaced brake pads also require a break-in period to better integrate with the old disc. Initially, the brakes may feel very stiff, and it typically takes a few hundred kilometers of driving before they improve. Some drivers aggressively brake to speed up the break-in process, but this accelerates brake pad wear and shortens their lifespan. It is recommended to drive normally and observe over time instead of forcing premature wear.

1. Sand particles entering: Tiny sand particles may occasionally get between the brake pads and disc, causing noise due to friction. This usually does not require repair, as the particles will eventually dislodge with driving.

1. Brake system malfunction: If the noise is accompanied by brake failure, inspection and repair are necessary. Missing or damaged brake disc screws or insufficient lubrication can also cause brake noise.

1. Severe brake disc wear: Abnormal wear on the brake disc can result from surface contamination, uneven material density, excessive operating temperatures, or incorrect installation torque. If deep grooves are worn into the brake disc, replacement is required.

1. ABS system activation: In vehicles equipped with ABS, a "clunking" sound during hard braking is normal. Pressing the brake pedal firmly will eliminate the noise.