Campagnolo direct mount rim brakes help

[usr]

At first glance it does appear as you say, that those screws make adjustments "in exactly the same swing path they move on when pulling the lever," but what I see happening is that it's pivoting the arm at a more acute (sharper) arc angel than when you squeeze the brakes, which operate different pivot points (nuts E/F).

I could be completely off the mark here, but at least that what it looks like is happening to my eyes, and what I've always understood to be the function of those screws (i.e., contact angle).

I'd say that the perceived more acute angle is just an illusion likely caused by focusing on a point closer to the shared pivot (the lower half of the caliper moving relative to the upper part) when watching the effect of the screws and taking in the big picture (because locally, between upper and lower part nothing happens) when watching the effect of cable pull.

Take a look at the spare parts PDF, I assume that you know which one I'm talking about. It's much clearer there than in the technical manual that all the parts share rotation around the DM bolt sleeves and that all you ever change with those little mushroom screws is their angle relative to the upper around that shared pivot (except for the pad holder itself of course, which rotates on a set of spherical clamping surfaces offering three degrees of freedom, four if you include the vertical slot)

[usr]

Admittedly, now that I've taken yet another look at my brakes, there is a certain gap in my mental model of Campag DM adjuster screws: why do we need a spring balance adjuster on top of this? (the spring pusher has the accustomed adjustment hex on the cable side and is fixed on the non-cable side)? Closest thing to an explanation I can come up with is "because that's how has always been done "

[c60rider]

I think the reason partly is that for standard dual pivot you can get them pretty central by just altering them around the central frame fixing bolt then fine tune each side with the adjusting screw. On DMs you've almost got two separate brakes going on that have to be adjusted individually and also in comparison to each side as they both have their own fixation to the frame. Added to that the cable throws another variable into the adjustment and I think that's why I found them so fiddly to set up. It certainly opens up a lot of potential for poor set up that perhaps the op is experiencing. The Campag PDF I put up didn't make it particularly clear either. I wonder if Graeme F-K is about who can clarify it.

[wilwil]

I have referred to that PDF before. Point 9, dia 10 in that PDF always mystified me. What are they talking about?
I haven't noticed any change in pad angle using the cross head screws, only pad distance from wheel. The shoes need to be less that 90 degrees to the arms and the only way to do this, it seems, is to rotate them by pushing the wheel guides inwards whilst they are loose and hold them in place with the brake lever.

[usr]

9/10 is about the hidden roller mechanism that transmits force from the long crossover lever (the one with the wire clamp bolt) to the wire-side-lever (on top of which the cable adjuster screw is sitting). The roller (in the diagram it looks kind of like a non-DM brake bolt, you can feel it operating of you lay your finger between tire and the middle of the brake while pulling the brake lever) needs to contact the non-wire-side lever or else all the wire pull would just push the wheel laterally from non-wire-side to wire-side without much clamping (wire side pad would be pushed, but only very weakly).

I believe that the situation 9/10 is warning of is extremely rare and likely requires some wildly skewed outer overpowering the spring, but the warning is important because the brake would Iook very close to operational (all the parts moving in the correct direction and so on) but would be terribly weak.