There are numerous characteristics associated with friction materials, few of which are absolute, for example the friction Coefficient (µ) varies depending on temperature, speed, pressure and energy level and no two dynamometer programmes will ever produce quite the same results. Choosing the most suitable pad for your application is a complex problem requiring careful evaluation of all the available information. To help you with this AP Racing have developed a rating system for the principal pad characteristics incorporatingboth the experience gathered by our engineers over many years and our special dynamometer evaluation carried out in-house on our state of the art facility.
The AP Racing dynamometer brake pad evaluation is based around a series of stops which represent the full range of conditions likely to be experienced in use. A composite dynamometer plot and an explanation of the AP Racing evaluation and rating systems is given below.





? Average friction: Overall mean friction coefficient calculated over the complete test cycle. (Fig 1.)

? "Bite": Initial friction at the start of the stop.
Rating 1 to 5. (5 = Good, 1 = Poor) (Fig 1.)

? Fade: Drop off in friction coefficient from stop to stop when used for very hard braking. Calculated from last 4 stops on test plot on a scale of 1 to 5. (5 = No significant fade). (Fig 1.)

? Average pad wear: A comparative rating of pad wear across all conditions.Rated on a scale of 1 to 5 ( 1 = best).

? Plot Shape: The shape of the friction plot during a brake application. High initial "bite" with friction gradually decreasing through the stop as speed drops off is considered to be the easiest to control (most "user friendly"). A climbing friction level through the stop is considered the most difficult to control (least "user friendly") although some pads with this characteristic are extremely popular due to their overall high friction level and fade resistance. Assessed types 5 to 1. (Fig 2.)

? Comfort / Noise: Does the pad promote judder or brake squeal ?. Important on road car applications but not usually a consideration for racing use.

? Disc Life: Does the pad promote high disc wear or cracking?. Especially important on road car applications. Rated on a scale of 1 to 5 ( 5 = best).

? Effective Temperature Range: The temperature range within which the pad material can be considered effective should be used as a comparative guide only as temperature measurement techniques vary significantly and the true picture must include the energy level (quantity of heat). Pad temperatures are affected by disc mass and cooling. Rated 1 to 5 (1 = 200°C / 2 = 350°C / 3 = 500°C / 4 = 650°C and 5 = 800°C).

? Suitable Area of Use: The areas for which the pad material is considered most suitable. This is a subjective assessment relying on the pooled experience of AP Racing engineers over many years. Contact AP Racing Technical Section for guidance.

? Pad Material Performance: The table below provides the ratings given for the characteristics described on the this page. The table results are AP Racing’s own, determined from our dynamometer testing and may differ from manufacturers own specifications.

? Y denotes suitable, X denotes not suitable