I was out the door to ride when I noticed a flat rear tire... sigh.
Brought it in, fixed it, and was hooking the straddle cable back up to the cantilever brakes when I noticed a pad dragging. The brakes are SunTour XC Pro's, which require the spring tension to be adjusted with a 13mm wrench. Carefully turning the wrench didn't seem to be increasing the tension, and I eventually realized that the spring had failed. <insert another sigh here>
okay, it was clear that the ride was cancelled, so the rest of the bike clothes come off.
Removing the brake arm and spring revealed that the bent end of the spring was no longer at a right angle to the coil. Instead, it was bent over and had pulled out of the mating hole.
There was a crack at the bend, which becomes visible upon closer inspection...
I had another one of these springs break in 2005, after only 5 years of use. This one failed after 22 years of use, so I guess that's not bad??
SunTour used a similar style of spring in their first generation SunTour Cyclone rear derailleur, and they also have been known to break at this sort of bend. I've had it happen twice, and have picked up spare derailleurs in order to have a source of replacement springs. Fortunately, I picked up a spare set of the XC Pro brakes after the first spring failure, so I'm prepared for two more springs to break. After that, I'm switching to the spare set of Shimano canti's that are also in the parts box.
Steve in Peoria