Originally Posted by
FBinNY
If you only hear the noise with the brake on, and not while pedaling and coasting, then it's a good bet that it's brake issue, and not related to the spoke disc, or anywhere near the hub.
Like HillRider I suspect that it's the rim joint passing the shoes, but it could be anything on the rim as it passes the shoes. Also, it might be play in the brake's pivots which click as the joint bumps the shoes.
Try this experiment. Find a hill you can coast down with decent speed. Remove the rear wheel and mount it backward (cassette on left) making sure the chain is over the hub as it normally would be. Push off and coast up to a decent speed and apply the brakes. Is the clicking better/worse or just different, if so it's the rim, and the solution is to use a file or sandpaper on a block to improve the rim seam slightly. Don't strive for perfection as you don't want to remove more metal than necessary, and the brakes will finish the job over time.
I think you're on the right track. Given I can't detect the problem just spinning the wheel and braking, I reckon it requires force/speed of actually being in motion to jog the brakes enough too make the noise. The brakes seem pretty solidly put together too.
The seam in the rim is detectable but quite slight, and very similar on both sides of the wheel though so if it is this, I doubt it will sound much different if I flip the wheel. I'll have a bash at it with a file though, and see if this improves things.
It's chucking down with rain today so may be a couple of days before I get some free time to experiment and come back with an update, but thanks for your help (and everyone else's too)