Edited on 2015-02-21 20:37:08
Edited on 2015-02-21 20:35:01
From what little I have ascertained, balance can be worked out simply by piston area. If you increase the piston area, you get more clamping force and more stopping.
The area of the pad should not matter in this regard. Twice the pad area simply means 1/2 the pressure loading on the pad face but the SAME clamping force.
And since Friction Force = mu * normal force, there is no area term.
Series I, II, and the Volvo all have the same piston area - either a single 2.125 or a pair of 1.5's or the mix and match 3-cyl Series II. (Frankly, someone has to explain that one to me!)
So none of these should change the balance.
HOWEVER, people refer to the Volvo as an "upgrade."
The only significant difference I can see is the pad area which should have wear and fade benefits.
But I'd really like to hear from someone who had Series 1 Dunlops on 3" bolt centers and upgraded to the Volvo 240 series caliper which is supposed to be a bolt on (3" centers.)
The only area upgrade that is OE-like are the 2.25 used on Nissans and Toyotas which should produce about 12% more clamping force.