Squealing Brakes and Spinning Rotors

When I was a Customer Relations manager for Daimler-Benz, a lot of customers called and complained about this phenomenon which, for some inexplicable reason, was always loudest when hitting the brakes while backing up.

I found that using the brakes hard a few times when starting out, prevented the phenomenon from happening.

One engineer reasoned that the chattering was caused by a thin film of oxidation which developed on the rotor during the night after condensation formed. The unevenness of the friction caused the brake pads to chatter and was made worse by the fact that break pads are relatively light, not fixed in place but float loosely until the brakes are applied.

I can not vouch for the efficacy of his diagnosis but the hard use of the brakes when first starting out did work, until the next day and of course had to used hard again.

Brake pad wear did not appear to be affected by the "cure"

L.J.

I think it has to do with the materials that the rotors and the pads are made of. I have put 5 sets of brake pads on my vehicle that has 150K on it and never had a problem until this last set. I figured giving it 2 weeks to "break" the pads to the rotors, but 6 months later I still have a screach. It is not as bad as it started out, but it is still there. I have added twice as much as normal brake lube between the pad and the caliper so I know that is NOT the issue. Now that most of these components are made in China ( I know the rotors are) I am sure there is something in their recipe that causes these two parts to dislike each other. All braking doesn't seem to be any different which is the key factor.

You've hit on a very common and frustrating issue, and your intuition about the materials is absolutely correct. Persistent screeching like you're describing, especially after ensuring the hardware is properly lubricated, almost always points to a material compatibility and vibration damping problem between the pads and rotors.

Why New Pads Can Screech on Old Rotors:

1. The "Break-In" Didn't Take: The goal of break-in is to transfer a thin, even layer of pad material onto the rotor surface. This is what creates optimal friction and quiet operation. If this layer doesn't deposit uniformly—or if the new pad material is incompatible with the existing layer from the old pads—it can lead to high-frequency vibrations that you hear as a screech.
2. Rotor Surface Condition: Your new pads are mating with rotors that have a history. Even if they look smooth, the microscopic surface is conditioned by the previous 5 sets of pads. A new pad formulation might not interact well with that specific "history" etched into the rotor.
3. The Core Issue: Friction Formulation & Dampening: You are right to suspect the "recipe." Brake pads are complex composites. Softer, quieter pads often use more organic or ceramic compounds, while harder, performance-oriented pads might be semi-metallic. The screech is often a stick-slip vibration. Manufacturers use specific additives, lubricants (like graphite), and even embedded shims to dampen these vibrations. A slight change in the formula can make a huge difference in noise.

Actionable Steps You Can Take:

• The Most Reliable Fix: Given that the noise has persisted for 6 months, the most straightforward solution is to resurface or replace your rotors and install a fresh set of pads from a reputable, known-quiet brand (look for "ceramic" formulations for daily driving, as they are typically quieter). This gives you a clean slate and ensures compatibility from the start. A proper break-in procedure is then critical.
• A Potential Interim Fix: You could try an aggressive re-bedding procedure. Find a safe, empty road and perform a series of 8-10 medium-hard stops from about 40-50 mph, allowing for cooling drives in between. This can sometimes force a proper material transfer and quiet things down. Only attempt this if your brakes are in full working order.

Your experience is a perfect example of how brake performance is a system-level issue, not just about individual components. The fact that your stopping power is unaffected while the noise persists is a classic sign of this material compatibility challenge.

We've written a more detailed guide on selecting brake pads for quiet operation and the science behind break-in procedures. If you're interested, you can find it here: https://frenobrake.com/what-causes-brake-squeal-and-how-to-solve-it/

I have 7 cars and no squeeker's , its simple when you wash you car wash your roters. Also when installing new pads use the lub supplied with the pads. If not use a copper type lube between the cylinder piston and the pad.

" Also when installing new pads use the lube supplied with the pads."

The industry seems to be unsure which method is best: some provide lube. Others provide a thin contoured steel spacer stamped from what appears to be tempered shim stock. Others provide a simple flat shim coated in a rubber compound of sorts.

Frankly, I have not made any comparisons so I have no opinion on which is best.

What is interesting is that the cost to manufacture top quality friction material is only pennies more than the run-of-the-mill junk from questionable sources.

That much was made clear to me by production engineers at Raybestos many years ago. It's also interesting to see performance comparisons between the high quality materials and the pads peddled by many auto parts stores. That too was a surprise.

When replacing brake pads, it's best to spend a few bucks more and buy a respected name when choosing a friction material.

L.J.

One thing people forget to do is wash the oil off the rotors before installing them. Manufacturers apply a thin coat to keep them from rusting. The oil then gets on the pads and can cause the leading edge to slip and cause chatter. Glazing from the oil can cause squealing.

Then again older pads can squeal because some people don't know that the pad wear sensor IS SUPPOSE TO DO THAT! LIKE MY KIDS!