Brakes: Rotor versus Bell area!

[1975DCS]

I have now fitted my AP's and they are a nice 330 mm.

But if you compare this 330 mm AP's with factory fitted stuff like on Porsche, BMW and Audi you can see a big difference in the space actually used for braking and the bell. The AP's have a very large bell area and a relative slim rotor (better said: pad height)*. Where as the Audi's and Porsches have a smaller bell area and a less slim rotor.

is there any reason for this difference? + and -?

* It is like 205/55/16 versus 205/50/17; they both have the same diameter, imagine the rim as bell diameter...

[jeroen]

that means that the ap's will brake harder because the centre line is of a larger diameter! but the brake pads will wear faster,and the surface can become hotter.

[Pembo]

It is all about swept area. Calculate the area that is from min diameter of pad and max diameter of pad. That is swept area and is key to the braking effectiveness. Your pad is therefore important as too is the pad material, operating temperature and fluid used. Loads of new materials out but be aware of disc wear rates and braking noise betwwen disc and pad.

[1975DCS]

that means that the ap's will brake harder because the centre line is of a larger diameter! but the brake pads will wear faster,and the surface can become hotter.

Interesting stuff!

[1975DCS]

It is all about swept area. Calculate the area that is from min diameter of pad and max diameter of pad. That is swept area and is key to the braking effectiveness. Your pad is therefore important as too is the pad material, operating temperature and fluid used. Loads of new materials out but be aware of disc wear rates and braking noise betwwen disc and pad.

If I read und understand correctly: the swept area is less with the AP brakes then on Porsche stuff (if both are 330 mm outside diameter)? And this outcome is as Jeroen describes it?