Bicycle Mechanics - recessed brake on older fork

When I first mounted it (Shimano BR-R600, front) 2 months ago it would not tighten down fully. I put a few spacers in front (thanks Sheldon!) so the pivot nut would not prevent the bolt from tightening down and that worked for a while. Now the pivot nut is interfereing with the movement of the outer caliper arm and so when I break it clamps down good and tight, but when I release the break the pivot bolt grinds into the back of the outer arm thus preventing it from recoiling back in to an open position. The odd part is that the nut is still tight and there is no wobble.

After looking at the technical data on the Shimano site I have come to the conclusion that it is indeed not tight enough.

Could (carefully) hack a few mil. off the pivot bolt thus allowing the nut to tighten more.
I already have a 12mm pivot nut--don't think they make em longer than that. Is it possible to buy a longer pivot bolt for this type of brake and perhaps even remake it into a non-recessed R600?

On another subject, I noticed that my break cable (not casing) is kinky in a few places...can I leave it or should I replace it?

Thanks.

I'm a bit confused as to which bolts are rubbing where. Is the bolt that goes through the fork rubbing on the back calipers, or is it the bolt that is the pivot between the two calipers rubbing somehow. It sounds like your fork was too thin for the bolt set that came with your brakes. Perhaps you have a traditional frame and this set was intended for a newer and fatter carbon fork.

It sounds like the mounting bolt is hitting your caliper arm which is closest to the fork. Yes?

If washers/spacers won't make up the space, then I don't see any reason cutting down the mounting bolt should be a problem other than removal of rust protection on the bolt, or messing up the threads when you hack saw it. but if you grease it enough, that shouldn't be a huge issue.

If you do hack saw it, then put a nut over the bolt, down past the point where you're planning on cutting, then after you cut through, un-thread the nut, and that will smooth out the threads, so you can use the bolt with any correct nut.

you should be able to do the same thing (although in reverse) with internal nut threads. put a bolt in (allen bolt?) past the threads that are being cut off, then thread it out after you cut the piece off.

good luck

Thanks Orange Leader.
Just to clarify...the R600 has a bolt that mounts onto the fork that runs through the inner caliper arm (rubs) and a second bolt that acts as the pivot between two arms off to one side (does not rub). On the Shimano spec sheet the bolt that mounts onto the fork is called the "pivot bolt" the back of which rubs the outer arm. I messed up in the original post and said the "nut" rubs...and we all know what kind of trouble that may cause...