Is overhauling dual-pivot caliper brakes due when the centering screw is ineffectual?

Question

The balancing/tensioning/centering screw on my rear dual-pivot (rim) caliper brakes is no longer effective. Is it a good idea to disassemble the calipers down to individual pieces, say once every two years of regular riding, to get rid of any grit that might be contributing to this?

Is it too difficult to completely reassemble, and that's why it's advised to only soak the full body (minus the pads) in a degreaser to overhaul (as opposed to a disassembly that exposes the spring)?

And while tuning/overhauling, is it a good idea to isolate the leverage of rear brakes by pulling the exposed part of the cable rather than using the lever?

Answer 1

There's not a generic answer because the sole unifying design element of dual pivot brakes is that there's a center pivot for one arm and an offset pivot for the other. The way the pivot hardware and centering screw works is different among different designs. Some use set screws for the pivot adjustments, some use locknuts, some make it easy to disassemble them, some don't, etc.

When a brake does the kind of thing you're talking about, typically one or more of the following are true:

• The screw's adjustment is maxed out because the initial centering of the caliper (done with the mounting nut) was too extreme.
• The spring is bent (they can sometimes be bent back).
• Too much friction at the spring contacts (needs cleaning/lubrication).
• Loose or damaged hardware or pivots.
• The pivots need cleaning/lubrication.

When going "beyond the basics" with servicing a caliper, it often will be easier in the end to just pull it all the way off the bike, cable completely removed. This is a little subject to what brake it is and what's going on with it.