Because the rotors are a larger diameter, the calipers mount further
out as well. They will rub against the wheel if you use a 14" wheel.

As to the benefit, it is easier to stop a spinning object if you grab
it further out. Yes, if you have a larger swept area, that too will
help, but by simply using a larger radius where you apply the
clamping power, it is easier.

On Feb 19, 2006, at 3:00 AM, Robert Smythe wrote:

> Forgive my usual ignorance but I dont have both sets of parts,
> stock and SA
> caliper/discs staring me in the face.
>
> If it is the case that the pistons are the same, the pads/swept
> area is the
> same, is the only "bigness" to the SA brake system the vented
> rotor? There
> must be more to it, if the brake disc doesnt have a 0.5" larger
> radius, why
> does one need 15" wheels?
>
> Robert
> 90 MV