(L to R): Stock, SSH, SS S-sport
With the reformulated SS-H pads, Endless engineers stumbled upon a combination of materials that turned out to be effective at noise reduction without the usual sacrifice of friction coefficient or feel. We say stumbled because the new formulation turned out to work by mistake. Endless discovered that, by using a porous compound and a proprietary (but not necessarily special) additive, it was able to reduce pad noise even under cold conditions. Ironically, this is contrary to conventional brake pad knowledge, which says pad material porosity contributes to increased brake noise, because the pores collect moisture overnight and create noise the next morning, before the pads come up to temperature and cook off moisture.
Endless USA provided a set of its normal street performance (SS S-sport) pads and new, quieter SS-H pads for testing on a stock Lancer Evolution IX. To accentuate the effects of pad feel, bite and release, we used stiffer stainless steel braided brake lines and ATE Super Blue brake fluid (with a higher than usual boiling point) to resist the effects of hydraulic fade under testing temperatures.
Without access to a true brake dyno, we couldn't test the friction coefficient of each pad with temperature. And since bite, release and noise are also fairly subjective to measure, we resorted to our standard 80mph-to-zero stopping test and noted how the pad sounded and felt as temperatures rose. To be expected, overall stopping distances were fairly similar; the car was on the same tires and was tested on the same day. We also spent significant time using each type of pad on the street.
From the outset, Endless' standard formulation SS S-sport street performance pad was noticeably louder than stock or the SS-H. Squealing was audible on nearly every low-speed braking application, making it annoying to drive around town. This pad sounds like a light race pad, but doesn't stop like one since the average friction coefficient (as tested by Endless) ranges from 0.35 to 0.45, depending on temperature. Pedal feel is improved over the stock pad (which we're not fond of anyway), but actual braking force is not much better. Also, this pad has no strong bite, the force being progressive with increased pedal pressure. For whatever reason, the pad seems to engage ABS later than the SS-H pads.
The new SS-H pad is definitely an improvement over stock in terms of pedal feel and consistency. Braking force seemed stable with repeated application, which we saw over several stopping tests. However, the braking force and bite are still not up to 100 percent track-only use. The pad has a smooth, progressive, linear braking force with the application of pedal pressure and the pads are nearly as quiet as stock. Squeal only happens slightly, during very light pedal pressure at very low speeds. In addition to the noise reduction, the SS-H is easy to drive like stock pads, but with improved pedal feel, consistency and ABS performance.