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      09-12-2012, 06:40 PM   #13
aleckzandr's Avatar

Drives: '09 n54 e92xi, 6mt, kw v3
Join Date: Sep 2009
Location: Colorado, USA

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2009 335xi  [4.22]
^ Sounds like a good setup to me. Are the rear pads a bit softer? If so, I think that is good idea. I have been using Pagid Yellows all around but am considering Orange in the back to bring up the heat in the rear (yes, you heard me correctly, I think the rears are running too cool, my rotors are wearing faster - and the pads less - in my rear brakes and it's not DSC, I drive DSC off 24/7/365 snow/rain/shine/track/street)... What brake pads were you using previously? What tires are you running?

... and one of my favorites:

Friction is the mechanism that converts dynamic energy into heat. Just as there are two sorts of friction between the tire and the road surface (mechanical gripping of road surface irregularities by the elastic tire compound and transient molecular adhesion between the rubber and the road in which rubber is transferred to the road surface), so there are two very different sorts of braking friction - abrasive friction and adherent friction. Abrasive friction involves the breaking of the crystalline bonds of both the pad material and the cast iron of the disc. The breaking of these bonds generates the heat of friction. In abrasive friction, the bonds between crystals of the pad material (and, to a lesser extent, the disc material) are permanently broken. The harder material wears the softer away (hopefully the disc wears the pad). Pads that function primarily by abrasion have a high wear rate and tend to fade at high temperatures. When these pads reach their effective temperature limit, they will transfer pad material onto the disc face in a random and uneven pattern. It is this "pick up" on the disc face that both causes the thickness variation measured by the technicians and the roughness or vibration under the brakes reported by the drivers.

With adherent friction, some of the pad material diffuses across the interface between the pad and the disc and forms a very thin, uniform layer of pad material on the surface of the disc. As the friction surfaces of both disc and pad then comprise basically the same material, material can now cross the interface in both directions and the bonds break and reform. In fact, with adherent friction between pad and disc, the bonds between pad material and the deposits on the disc are transient in nature - they are continually being broken and some of them are continually reforming.
KWs - Vorshlags - APEX EC-7s - "My garage" has suspension install pictures.