I picked up a set of Raybestos Advanced Technology ceramic pads today (ATD923C) for a '06 Corolla, and noticed that the edge code was "FF." According to the information that I have found, the pads have a coefficient of friction between 0.35 and 0.45.
Are these accurate indicators of the pad's performance? Are these numbers meaningful? Or is this another "nearly worthless" exercise, such as comparing engine oils solely through the specs on the product data sheet?
Here's a picture of the pad:
Here's some info that I found:
http://www.hotrodders.com/forum/hawk-brake-pads-133814.html (7th post)
http://www.tscperformance.com/supra_dot.html
Quote:
An edge code is a means of identification that may be used to describe the initial frictional characteristic of any brake lining.
Typically, a two-character code (e.g. EE, FF, GG, HH, etc) is used on specific friction formulation. These characters represent the coefficient of friction when a 1" square piece of friction material is subjected to varying conditions of load, temperature, pressure and rubbing speed on a test apparatus known as the Chase machine.
The coefficient of friction measured by the Chase test describes the relationship between the two forces acting on the friction material. A clamping force is exerted on the friction material, resulting in a frictional or resistance force. A low coefficient of friction means that very little of the clamping force is transferred into resistance force. On the other hand, a high coefficient of friction means that given the same level of clamping force, a higher resistance force is generated by the brake pad.
For example, a pad that carries an HH code has a normal coefficient of friction of 0.55 or higher, and a hot coefficient of friction of 0.55 or higher.
The first letter of the code represents the normal friction coefficient. This is defined as the average of four test data points measured at 200, 250, 300 and 400 degrees Farenheit.
The second letter of the code represents the hot friction coefficient based on a fade and recovery test. We all should know what brake fade is. If you've ever had to use the front brake extensively and found that its effectiveness quickly diminished, that's fade. Recovery is basically the period where the brakes are gradually cooling off.
The hot friction coefficient is defined as the average of 10 data points located at 400 and 300F. On the first recovery cycle of the pad; 450, 500, 550, 600 and 650F. On the second fade cycle; and 500, 400, and 300F on the second recovery cycle.
The range of friction coefficients assigned to each code letter are as follows: C = less than 0.15. D= 0.15 to 0.25. E= 0.25 to 0.35. F= 0.35 to 0.45. G= 0.45 to 0.55, and H= over 0.55.
From http://www.satisfiedbrake.com
Are these accurate indicators of the pad's performance? Are these numbers meaningful? Or is this another "nearly worthless" exercise, such as comparing engine oils solely through the specs on the product data sheet?
Here's a picture of the pad:

Here's some info that I found:
http://www.hotrodders.com/forum/hawk-brake-pads-133814.html (7th post)
http://www.tscperformance.com/supra_dot.html
Quote:
An edge code is a means of identification that may be used to describe the initial frictional characteristic of any brake lining.
Typically, a two-character code (e.g. EE, FF, GG, HH, etc) is used on specific friction formulation. These characters represent the coefficient of friction when a 1" square piece of friction material is subjected to varying conditions of load, temperature, pressure and rubbing speed on a test apparatus known as the Chase machine.
The coefficient of friction measured by the Chase test describes the relationship between the two forces acting on the friction material. A clamping force is exerted on the friction material, resulting in a frictional or resistance force. A low coefficient of friction means that very little of the clamping force is transferred into resistance force. On the other hand, a high coefficient of friction means that given the same level of clamping force, a higher resistance force is generated by the brake pad.
For example, a pad that carries an HH code has a normal coefficient of friction of 0.55 or higher, and a hot coefficient of friction of 0.55 or higher.
The first letter of the code represents the normal friction coefficient. This is defined as the average of four test data points measured at 200, 250, 300 and 400 degrees Farenheit.
The second letter of the code represents the hot friction coefficient based on a fade and recovery test. We all should know what brake fade is. If you've ever had to use the front brake extensively and found that its effectiveness quickly diminished, that's fade. Recovery is basically the period where the brakes are gradually cooling off.
The hot friction coefficient is defined as the average of 10 data points located at 400 and 300F. On the first recovery cycle of the pad; 450, 500, 550, 600 and 650F. On the second fade cycle; and 500, 400, and 300F on the second recovery cycle.
The range of friction coefficients assigned to each code letter are as follows: C = less than 0.15. D= 0.15 to 0.25. E= 0.25 to 0.35. F= 0.35 to 0.45. G= 0.45 to 0.55, and H= over 0.55.
From http://www.satisfiedbrake.com
