Glazed and Confused – Brakes, Brake Pad Glazing and Stopping the Car

Not The Glazing You Hoped For
Glazing. At first, sounds like a sugary treat. But there’s nothing sweet about this service concern. No, it’s not a new donut, or frosting spread on your car’s brake pads, but rather something that adversely occurs to brake pad friction material.

A minor glazing issue will usually self correct. A major one requires professional rework of the brake system, to assure that you have a safe auto. So, let’s start out by talking about brakes, and how they work.

Process, How Brakes Work
To understand any failure, it’s first important to understand how the system is supposed to properly work. Automotive brakes are basically an energy conversion and storage system. The physics of car brakes are pretty simple. To slow down and stop your car, your brake system turns kinetic energy (the movement of your wheels) into heat energy, by way of friction applied by your brakes to the wheels.

This heat is then dissipated by the brake pads, brake rotors and though the brake fluid, into the air. Once all the kinetic energy of the wheels has been converted to heat energy by the brakes, your car stops. Pretty simple, right? By nature and design, brakes work in adverse environments, and do it well for tens of thousands of miles.

The Parts
There are five major components that make up your vehicle brake system – Brake Master Cylinder, Brake Lines and Hoses, Brake Calipers, Brake Pads and Brake Rotors.

Of these, the last three, pads, calipers and rotors, are the usual culprits in a brake glazing concern, as they are most effected by heat, and most subjected to adverse conditions. During normal street use, brake rotors and pads normally see temperatures climb past 200 degrees Celsius, or 392 degrees Fahrenheit! That’s almost double the temperature required to boil water.

These are also the parts that should be inspected, and serviced as needed, on a regular basis, ideally every time your vehicle is in for service. Of all the systems on your car, your brake and steering are arguably the most critical. 

So What Is Glazing?
Quite simply, brake glazing or “crystallization” is hardening of the brake friction material due to excessive heat. To complicate matters, the hard glazing typically transfers from the pad surface onto the brake disc (rotor).

That means the friction component is significantly diminished, resulting in reduced braking performance and often a noticeable brake shudder or vibration when brake pad material builds up unevenly on the disc. You may also see it manifest as cracks or fractures on the brake pads.

Glazing results in excessive stopping distances, and it can happen without the driver’s knowledge. It’s called “glazing” as the normally rough surface of the brake pads takes on a shiny, or frosted appearance.

Types
It’s important to distinguish between two types, one, which is light surface glazing, and is cleaned off with normal use in a few hundred miles.

The other, is deep and permanent glazing that transforms the structure of the brake pad, and often leads to cracking, or failure of the friction material.

Glazing Reasons
There are several reasons for brake pad glazing on passenger cars and trucks.

• Repeated hard and rapid braking at higher speeds raises the temperature to the point where it exceeds the limit of the pad material. This is usually evidenced by a strong and pungent burning smell.

• Driving with a foot on the brake pedal, called “riding the brakes” or dragging the brakes, keeps the pads in contact with the rotor. This constant rubbing spikes temperatures beyond the limits that passenger vehicle pads are designed for. Usually, but not always, evidenced by a strong and pungent burning smell.

• Continuous application of the brakes when coming down a steep hill can result in glazing. Often evidenced by a strong and pungent burning smell.

• Mechanical or hydraulic failure of the caliper can cause glazing. The caliper forces the pads to constantly rub against the rotor, like riding the brakes or coming down a steep hill.

This is the most dangerous cause of glazing because it often occurs without the driver’s knowledge. There are clues, a strong burning smell, and also the brake rotors will show signs of overheating, blue lines or areas of discoloration. Brake rotors may warp, causing brake pedal pulsation, or even get bright red and glow from the heat.

Glazed Brake Correction
Light Glazing, is self correcting, and will often clean off in a few hundred miles though normal brake use. This is the most common type and is often caused by “riding the brakes”.

Deep Glazing, where brake pad breakdown or damaged has occurred, can only be addressed in one way, the brake pads should be replaced and the rotors cleaned or replaced. Glazing compromises and ruins the friction material. The calipers and hydraulic system should be examined for mechanical problems or failure.

If glazing happens often, with no mechanical cause, the driver will need to evaluate their driving style. They may need to learn not to ride the brakes or to stop their vehicle constantly hard.

Other Options
Brake Pad/System change, though at Altantic Motorcar we are advocates to preferably install the factory designed parts, we realize that some clients will want to use their vehicles in different ways, some for performance or track use.

In these cases, we may be able to offer a superior designed brake pad, brake lines, or rotors, more suited to this level of “spirited driving”. Repeated failure of brake pads, with no underlying cause other than driving style, would be a good diagnostic indicator for this option.

Professional Brake Service
Brakes are one of those systems that appear low tech, and is often the first thing that folks tend to “farm out” or attempt themselves, thinking they are saving money. If there is one repair that we see again and again, that is subject to redo after a “DYI”, it is the brake system.

Over the last 35 years we have corrected more “do it yourself brake jobs” than any other system on the car. Incorrect parts, misdiagnosed, unnecessary repairs or parts replacement, seem to be the norm here.

On most European cars, calipers rarely need replacement, yet it’s the first thing we see done by those not familiar with these cars. Very often a waste of money, and a high quality factory part is replaced with a low grade aftermarket alternative. Likewise, brake fluid exchange, a simple service to prolong the life of your brake hydraulic system, is one of the most neglected.

Today’s complex ABS brake systems, electronic calipers, and computer controlled traction systems, require special training and equipment to service and diagnose.

The simple truth is that professional brake service, on one of the most critical safety systems of your car, is really no more costly in the end, by having a professional do it right, the first time. In fact, amortized over the life of a professionally serviced brake system, it’s remarkably inexpensive.