Tech Stuff

Brake pad and rotor technology

Brake pad codes

The edge of a brake pad will feature a list of engineering codes. If you know how to read these codes, you can determine who made them, the composition of the friction material and the pad’s CF (coefficient of friction) based on SAE standards.

The first group of characters indicates the manufacturer. The second group indicates the formulation of the pad composition. The third group indicates the pad’s CF. The CF rating isn’t a guarantee of how the pads will function on a specific vehicle or application, but will provide a rough idea.

Coefficient of friction (CF) codes:

– 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

– H.........over 0.55

– EE.......0.25 to 0.35 at 250 and 600 degrees Fahrenheit. Fade at 600 degrees F possible.

– EF.......0.25 to 0.35 at 250 degrees F; 0.35 to 0.45 at 600 degrees F. 2% to 44% fade possible at 600 degrees F.

– FF.......0.35 to 0.45 at both temps. 0-22% fade possible at 600 degrees F.

– GG......0.45 to 0.55

– HH......0.55 to 0.65 carbon/carbon only. OK up to 3,000 degrees F.

FE pads tend to fade when hot. EF pads may tend to not grab when cold.

Physical pad design

Depending on the vehicle or intended application, pads may feature one or more slots. These slots in the friction material pad help to clean dust out of the rotor-to-pad contact area, and provide thermal expansion of the friction material segments, which aid in preventing pad material stress cracking.

To aid in identification, the edge of the pad material will feature a code that indicates the manufacturer, the friction material composition and the SAE-rated coefficient of friction.
<p>To aid in identification, the edge of the pad material will feature a code that indicates the manufacturer, the friction material composition and the SAE-rated coefficient of friction.</p>

Pads may feature chamfers at the leading and exit edges of the pad. This is often used to eliminate or “tune” certain noise frequencies.

Pad bedding/break-in

As the pads mate with the rotor disc surface, and depending on the type of pad formula, a small amount of friction material is transferred to the disc surface, which increases braking efficiency. If the replacement pads differ from the original pads (in terms of friction material formulation), and are to be used with the original rotors (when changing pads but not the rotors), an initial break-in is recommended.

Drive the vehicle through a few moderate braking exercises in order for the new pads to “wipe” the disc surfaces of the previous embedded friction material. Then continue to drive with moderate braking (at speeds of around 35 to 40 mph) in order to “bed” the new pads to the disc surfaces. However, some brake pad manufacturers note that no bedding-in procedure is necessary with certain pads, so don’t make assumptions. Read the instructions (if provided) that come with the new pads.

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