The early setup is not a performance type dual piston since the pistons
are directly opposite each other rather than side by side. A side by
side dual piston would allow a longer pad with a higher proportion of
the friction area farther from the center of rotation of the rotor. The
newer setup has a larger piston, larger pads, slightly larger effective
rotor diameter due to the improved shape of the larger pad pushed by the
larger piston. The newer rotor is thicker and less likely to warp.

Mark

David Beierl wrote:
> At 08:44 PM 2/1/2012, Jim Arnott wrote:
>> I guess my question would be, "Going from a dual piston caliper to a
>> single piston caliper improves things how?"
>
> It gets you a thicker rotor. It makes the pads slightly harder to
> change. The caliper is simpler and likely less expensive. I can't
> remember whether the pads are larger.
>
> Yours,
> David
>