Auto aftermarket reading: brake pad noise, disc scoring and pad damage — causes and handling

Abstract

This workshop reference classifies brake problems into four groups — noise, disc scoring, crumbling or detaching friction blocks, and brake failure — with human vs. product causes and handling steps. On noise: after replacing original pads the disc is often already scratched by those original pads; shops should inspect the disc first and resurface or replace it, recording the driver's written consent on the repair order. Where the disc is smooth, noise can come from offset pad fitting (reinstall), manufacturer size mismatch of up to 3 mm on friction blocks (resurface the disc or run in), road debris trapped between pad and disc (remove debris, resurface), or loose pad accessories (re-fasten or replace).

On product factors, the article notes that while national rules ban asbestos pads, some small makers still produce them; semi-metallic asbestos-free pads run harder and may squeal, whereas the softer asbestos pads rarely squeal even on scratched discs — in such cases a pad replacement is needed. On disc scoring: where the disc is already smooth, scoring usually comes from uneven mixing in production; minor scratches under 1.5 mm deep need no disc replacement, just resurfacing. On crumbling: unchanged colour points to a product defect (replace); red or yellow discolouration points to a seized caliper or prolonged braking in mountains or at highway speeds (replace the pads and repair the caliper, not a product liability). On brake failure: freshly fitted pads that fail on installation are usually oil contamination during fitting (not a product liability); failure after driving through water pits quenches the hot pad and disc into a hard blue oxide layer — both pad and disc must be replaced, again not a product liability. The article closes with inspection-liability advice and a health note: asbestos pads are carcinogenic and nationally banned, so refuse unregulated asbestos-containing pads.

Key facts

• Always inspect first: check the disc for scratches before fitting new pads; resurface/replace and obtain written driver consent
• Size tolerance: friction-block width can differ by up to 3 mm between manufacturers of the same model
• Scratch depth: under 1.5 mm, resurfacing suffices — no disc replacement needed
• Crumbling colour cue: unchanged colour = product defect; red/yellow = seized caliper or prolonged braking (not product liability)
• Water-quench failure: hot pads and discs hitting puddle water form a hard blue oxide layer — replace both
• Asbestos note: asbestos pads are nationally banned for carcinogenicity; refuse unregulated asbestos-containing pads
• Liability advice: inspect the vehicle as early as possible once a complaint arises to preserve evidence

The original article is in Chinese; see the Chinese version for the full text. This page provides the English title, abstract and key facts only — translated and compiled from the original, without full verbatim translation.