Real User Experiences with Brake Pad Installation – HUSCH Braking
(1) Looking at the Removed Brake Pads, the Owner Said: "I Never Imagined the Brake Pads Could Get Like This!"
A car was up on the lift, with both rear wheels already removed. The owner was standing beside it, watching. What was being repaired?
A closer look revealed the mechanic was removing the rear brake pads. In just a moment, the old rear pads were off. Looking at the removed pads, the owner beside me said, "I knew the brakes felt off! There was noise, and they didn't feel sharp."
The owner even handed me the brake pad to see. Wow, the friction material was almost completely worn away. There were even clear friction marks on the metal backing plate of the pad.
I couldn't help but ask the owner, "Why wait until now to change them?" The owner said, "For the past few days, the pedal just felt wrong. I thought I'd wait a bit. But today, the noise when braking got much louder. I really never imagined the pads had gotten like this."
Fortunately, the brake rotors weren't severely damaged and could still be used. Only new brake pads were needed. If the owner had continued driving, the rotors would certainly have been worn out and ruined, requiring replacement during the repair.
At this point, let me briefly share the impacts of not replacing brake pads on time—what happens when they should be changed but aren't—primarily in two aspects:
Affects braking performance, creating safety hazards. When pad wear exceeds the specified limit, the friction between the pad and rotor may decrease, leading to longer stopping distances. In extreme cases, this can cause danger.
Affects other components of the braking system, increasing repair costs. Once the friction material on the pad is completely worn, only the metal backing plate remains. This plate then contacts the brake rotor directly. Since the rotor is made of cast iron, when two metal plates press and rub directly against each other, their surfaces become uneven and damaged. The rotor will be ruined and need replacement.
Furthermore, when pads are severely worn, it can cause the brake caliper piston to over-extend, damaging the caliper's rubber seals. This may lead to brake fluid leaks, affecting the entire brake system and significantly increasing repair costs. We've encountered this situation in our shop.
Therefore, as car owners, if we encounter any issues with braking during daily use, we must promptly have a professional mechanic check for potential safety hazards.
Don't worry that such an inspection will be charged. Checking brake pads is very simple, and in 99% of cases, mechanics won't charge for it. Just say "thanks for your help, mechanic" before and after the inspection.
(2) The Owner Changed His Own Brake Pads. He Saved Money But Almost Lost His Life.
A car's ability to stop relies entirely on the friction force between the brake pads and rotors. Press the brake harder, friction increases, and naturally, the stopping distance shortens. However, there's also a scenario caused by human error, which I'd like to share here. The owner said he changed his own brake pads but found the brakes unresponsive and felt like the car wouldn't stop. Our mechanic received a roadside assistance call and went to the scene. First, look at this picture of the front brake rotor. Can you see the problem?
The arrow points to grease. This substance should never be on the brake rotor. Where did it come from?
There was a lot of grease on the brake caliper and wheel hub. Following the grease trail, we finally found a large accumulation of grease here, as shown in the picture below. The brake rotor was also covered in grease, though it's not clearly visible in the photo.
The friction material of brake pads is mostly semi-metallic, which ensures sufficient friction force while preventing excessive wear on the rotor. Now, with grease all between the rotor and pad, the friction force was inevitably greatly reduced.
After removing the wheel and seeing this, our mechanic had a pretty clear idea of where the problem lay.
The mechanic gained a clearer judgment of the issue. It's worth noting that when replacing brake pads, a mechanic typically applies an anti-squeal compound to the back of the pad. This is completely different from common grease. Anti-squeal compound is heat-resistant and becomes semi-solid at high temperatures, whereas common grease turns into liquid. During braking, rotor temperatures can reach over 300°C. The melted grease flows onto the rotor, severely compromising braking performance.
Here is our professional analysis of common brake pad issues:
Brake Judder/Vibration:
Cause 1: Warping or distortion of the brake pad or rotor, related to material, manufacturing precision, or heat-induced deformation during use.
Cause 2: Vibration frequency generated during braking by the pad resonates with the suspension system.
Cause 3: Unstable or excessively high friction coefficient of the brake pad.
Impact of Friction Coefficient on Braking:
Both excessively high and low friction coefficients affect braking performance. Especially during high-speed emergency braking, a coefficient that is too low leads to unresponsive brakes, while one that is too high can cause wheel lock-up, leading to dangerous situations like skidding, loss of control, or even rollovers.
Relationship Between Brake Pad Life and Hardness:
Pad life is not necessarily directly related to surface hardness. In fact, if the surface is too hard, the actual contact area between the pad and rotor decreases, which may instead affect lifespan.
Factors affecting pad life include hardness, strength, and the abrasiveness of the friction material.
Impact of Driving Through Water on Brakes:
When wheels are submerged, a water film forms between the pad and rotor/drum, reducing friction. For disc brakes, since the pad area is smaller and the outer part of the disc is exposed, water is easily dispersed, so the effect is smaller. For drum brakes, it's necessary to gently apply brakes while driving to remove water droplets and use the heat generated by friction to dry the braking system.
Poor Braking After Installing New Pads:
Possible causes include: incorrect brake assembly installation, uncleaned/contaminated rotor surface, faulty brake lines or insufficient brake fluid, incomplete bleeding of air from the hydraulic system, excessively worn or substandard quality rotors.
Brake Drag (Pads Not Fully Retracting):
Possible causes include: faulty brake return springs, improper clearance or overly tight assembly between pads and rotor, substandard thermal expansion properties of the pads, or a parking brake that doesn't fully release.
Smoking During Braking:
Organic compounds in the brake pad can decompose and smoke at excessively high temperatures, forming an oily substance on the pad surface that affects braking. Possible causes include: excessively high brake temperatures (e.g., long downhill driving, frequent braking) or substandard organic content in the pad formulation/compound or unstable manufacturing processes.
Final Conclusion:
The core value of maintaining and upgrading your braking system is "using reliable certainty to counter unpredictable risks." Whether it's the excessive wear from ignoring warning signs as in Case (1), or the immediate failure caused by improper installation as in Case (2), the cost far exceeds that of a professional inspection and a standard replacement.