Don’t Ignore Brake Materials
by Michael Shade, IQS Editor
Until recently, I drove a 1997 Ford Escort, Old Rusty. At the tail end of winter, the car’s blower motor gave out, rendering the heater and defroster features inoperable. Each morning of the week following the motor’s demise, I would find myself trying to scrape a thick layer of frost off of the inside of my windshield, the concave nature of which was not even mildly hospitable to scraping. When the mechanic at the garage told me that it would cost $600 to fix the blower, I asked him to perform a general inspection of the car. I wanted to know if it was worth putting that kind of money into that kind of car if there was any chance that some other costly problem would present itself. He found that the sub-frame was rusted into oblivion (which is how the moisture was accumulating in the car’s interior and collecting on the windshield), a wheel bearing was loose (which meant the wheel could fly off as I drove somewhere) and that the engine was leaking oil from an undetermined location. Time for a new car.
Aside from the problems I’ve already mentioned, the car was beset by a host of other novel problems. The rear defrost didn’t work. The driver door would freeze open during particularly cold days, and I’d have to hold it shut as I drove. And let’s not forget the brakes – maybe about four years ago, the brakes started to make sort of a wub…wub…wub…wubwubwubwubwub noise, the frequency and volume of which was proportionate to the speed at which I began decelerating. The noise would be accompanied by vibration in the brake pedal. Pulling off of a highway could be terrifying, as maybe you could imagine. I learned while writing about friction materials some months ago that these symptoms are often construed to be indications of a warped brake disc. It would make sense; the rumbling conceivably could be caused by vacillating levels of contact between the friction materials and the brake disc, and if the rate of that vacillation corresponded to changes in speed, that would seem like that much more evidence of warpage.
I read, though, that this was not likely to be the case. Before we go further, it may be helpful to quickly go over how a disc brake works. A disc brake is a disc that’s mounted to the axle on your car. As the axle spins, the wheel and disc brake spin with it. Hovering above the disc brake is a stationary caliper that, when activated, squeezes around the disc, causing the rotation of the axle to slow because of the friction between materials applied to the caliper and the surface of the brake disc. You can imagine, if the disc were warped, that this would express itself somehow, either through vibration or through a noise. But according to articles written by seasoned mechanics, the problem of brake disc warpage is very uncommon, if not mythical altogether.
The much more likely cause of the kind of vibration that I was experiencing had to do with uneven distribution of the brake materials that were coming into contact with the brake disc. Over the course of a brake pad’s lifespan, the friction materials applied to the pad wear down. In some cases, they wear down unevenly. In other cases, the materials are transferred onto the surface of the brake disc, sometimes unevenly, and this also can cause vibration and other problems. The solution to this problem, not surprisingly, is regular maintenance of the brake assembly – replacing the pads when necessary, inspecting the brake disc for unevenly deposited friction materials, ensuring the proper functionality of the caliper, etc.
The problem that I had with my brakes was the fruit of my non-labor. Many of the problems that ended up crippling my car were problems that could have been avoided, or at least mitigated, by more aggressive maintenance. The brakes would have been a particularly easy fix. I guess this is an opportunity to commit to keeping my new car in the best shape possible. In the mean time, I commend Old Rusty to his new home at the scrap yard.