I might be wrong, but the diameter of the rotor doesn't increase the swept area...the pad area provided by the caliper dictates this, no?
I thought the larger rotor diameter simply improves the mechanical advantage due to it providing a longer lever arm...????
I've addressed this on my F3 front wheel conversion by filling my tires with helium.
You are correct that the pad area determines the swept area to a great extent. However, given the same pad size, unless my maths is way off (and it well might be), the swept area will increase with rotor diameter.
I just did a rough calculation to confirm this. Given a fixed pad diameter of 2cm (for arguments sake. I don't have actual pad diameter in front of me) a 2cm slice of a rotor with an outside diameter of 34cm gives a swept area of 201 square cms. A 2cm slice of a 32cm rotor gives a swept area of 188 square cms. An increase of around 7%. I am no expert and my maths is not the best so I'm happy to be told I'm wrong and have my mistake explained.
The problem may be we have different definitions of swept area. I've always taken it to mean surface area of the rotor the pad sweeps across. It may be there is a more refined (or completely different) definition of the term that I don't know. As I said, if you are looking for an expert in these things, don't look at me.
Also correct that the longer lever arm will provide greater mechanical advantage and hence better braking. Being lazy I conflated the two properties of my set up and ascribed them to the rotor to save on typing. I guess I should have known that there are too many knowledgeable people on here to get away with being lazy.
What I should have said is that given the increase in both rotor diameter and pad size the swept area of my set up increased by 37%.
LOL, as usual I'm probably guilty of too much reply. I tend to write a page where one sentence will do.
Just a quick edit. Obviously overall area of the pads would affect swept area and would somehow have to be included in the calculation. For example changing to a six pot caliper (assuming pad diameter was unchanged) would significantly increase the area. In the light of this thought it is clear my definition of "swept area" is incorrect. A quick look at the old and new pads I have shows my original 37% is little better than a guess. I would need to determine the overall area of the pads and relate that to the area of rotor contacted. I think I'll stick with saying it works better and leave it at that.
So in conclusion all I am willing to say with any confidence is that given equal pad size an increase in rotor diameter will increase the area of rotor swept.