adjust cantilever brake pads on Schwinn Mesa Runner
I'm trying to adjust the brake pads on a recently-acquired Schwinn Mesa Runner circa 1990(?). They are cantilever brakes, center-pull, and have the brand name "Sierra" stamped into them.
The pads have a grooved stud that goes through an eyebolt, with a curved washer at either end, and a nut at the other end. When I tighten the nut, the curved washers force the pads into a fixed position--and not the right position. I can't get them to toe in or even sit flat against the rim, so there's serious squealing.
I've read lots of good advice on the web, at Sheldon Brown's site as well as others, but nothing seems to work for me, as these brakes don't seem to have any adjusting screws anywhere.
Should I be trying to move the curved washers into different positions? This doesn't seem mechanically wise--putting the convex part of the washer against the convex part of the mount seems like it would soon fail.
What am I missing? Any advice?