The email said the pads squealed from the first week and that the workshop had already replaced eleven sets under warranty. Attached were four photographs, a video with wind noise, and a claim for 3,400 euros.
Brake noise claims are the hardest category to resolve, because the complaint describes a sound and the evidence is a part. What made this one close in nine days was not better testing but disciplined brake pad batch traceability from the first hour.
The Complaint: Noise at 800 km
The report described a low-frequency squeal between 40 and 60 km/h, appearing after roughly 800 km and worsening in wet conditions. Eleven sets from three different vehicles, all fitted within a nine-day window.
Two facts narrowed the field immediately. All eleven complaints came from one batch, and none came from the two batches shipped in the same container.
That pattern argues against a design or fitment error, which would have shown up across batches. It argues for something that changed within a single production run.
Day 1-2: Locking the Batch Identity
The carton carried a lot code and a date-shift stamp. The lot code resolved to a friction-material batch, and the stamp resolved to press 3, second shift, cure cycle 44.
- Friction material batch number and its incoming certificate.
- Press number, shift, and cure temperature log for that cycle.
- Backing plate lot and adhesive batch used on the same run.
- Shim supplier lot and the surface treatment applied to it.
- Quenching and post-cure oven records for the same 12-hour window.
Within two working hours we had all five records. This is not luck; it is the return on a labelling rule that requires every carton to carry both a lot code and a date-shift stamp, printed at source rather than applied later.
The shim lot was the first anomaly. Its supplier had changed the coating process three weeks earlier, and the new coating had a different surface energy — information that appeared in a supplier notice nobody had read.
Day 3-6: Reproducing the Condition
A recall of four sets from the distributor's shelf gave us material from the same batch. We ran them on a dynamometer against a control set from the previous batch.
| Test | Control batch | Claim batch |
|---|---|---|
| SAE J2521 squeal occurrence | 2 of 30 stops | 11 of 30 stops |
| Compressibility at 25 C | 0.14 mm | 0.19 mm |
| Shim adhesion, peel | 38 N/cm | 21 N/cm |
| Cure degree, DSC residual | 0.8% | 0.8% |
| Friction coefficient, cold | 0.38 | 0.37 |
The friction material itself was fine: cure degree matched, friction coefficient matched, compressibility was inside the drawing band. The shim adhesion was the outlier, at 21 N/cm against a 38 N/cm control.
That reading reframed the claim. This was not a friction formulation problem, which would have required a batch-wide recall. It was an interface problem between pad and shim.
We confirmed it by refitting eleven control sets with shims from the previous supplier lot. Squeal occurrence dropped to the control rate within 400 km on all eleven vehicles.
Day 7-9: Root Cause and Settlement
The root cause was the coating change on the shim, combined with a cure profile that had been tuned for the previous coating's surface energy.
The press parameters were within their documented window, so the process had not drifted. What had drifted was the assumption underneath the window, and nobody had re-validated it after the supplier's change.
| Action | Owner | Closed |
|---|---|---|
| Shim supplier reverted to validated coating | Supplier | Day 8 |
| Cure profile re-validated for both coatings | Supplier | Day 9 |
| Incoming check added: shim peel test per lot | Us | Day 8 |
| Warranty claim accepted in full | Us | Day 9 |
| Supplier change-notification clause added to PO | Purchasing | Day 9 |
The claim was accepted in full, including labour, and paid on day nine. That is faster than average for this category, and the speed came from being able to name a cause rather than negotiate a discount.
The expensive lesson was in purchasing, not production. A supplier process change had been communicated and never entered the change-control log, which is where most latent defects in this industry originate.
What Made the Difference
Four practices turned a six-week investigation into a nine-day one, and all four were already part of our brake pad batch traceability routine long before the claim arrived.
- Dual labelling at source: lot code plus date-shift stamp on every carton, never applied at the warehouse.
- A retention sample from every friction batch, held for 24 months and stored by lot.
- Dynamometer access on site, so a control-versus-claim comparison needed no external lab booking.
- A purchase order clause requiring written notice of any supplier process change.
The retention samples were the single highest-value item on that list. Without them, the dyno comparison would have been a simulation rather than a measurement, and simulations do not close claims.
The change-notification clause came too late for this claim but has since prevented two others. It costs nothing to write and is ignored by most buyers until a claim arrives.
Frequently Asked Questions
How long should a brake pad claim take to resolve?
Four to six weeks is typical when batch records are incomplete and destructive testing must be outsourced. With retained samples and in-house dynamometer access, nine to twelve days is achievable.
What is the first record to request?
The friction-material lot code and the cure log for that cycle. If the supplier cannot produce both within 48 hours, the investigation will be an argument rather than an analysis.
Are noise claims usually a material defect?
Roughly a third are. The rest trace to an interface component such as a shim, an installation error, or a rotor surface condition, which is why the batch comparison should test the whole assembly rather than the friction block alone.
Should retention samples be kept by lot or by shipment?
By lot. A shipment can contain several friction lots, and a claim almost always resolves to one of them. Keeping samples by shipment forces you to re-test goods that were never implicated.
Reference Sources
SAE J2521 — Disc and drum brake dynamometer noise and judder procedure.
SAE J661 — Brake lining quality control test procedure.
UNECE Regulation No. 90 — Replacement brake lining assemblies.
IATF 16949:2016 — Clause 8.5.6.1 on control of changes.
ISO 9001:2015 — Clause 8.5.6 on control of changes.