Since I started biking to work a few years ago, I have owned two late-seventies road bikes, which have each used centerpull brakes. Adjusting these brakes has always been the bane of bike-riding for me. As soon as I loosened the anchor bolt, the struggle began to pull the cable tight without losing my grip and letting the cable fly through the bolt. Professionals–and people who are a bit more serious about fixing up their bikes than me–generally use what is called a “third hand” tool. But, I like to avoid purchasing new tools as much as possible. I’ve come up with a couple methods that might help you in the midst of your own frustration.
The technique I used on my first bike (a Penn-Speed from J.C. Penney) was to take a narrow rope or clothing line and tie it through the brakes with a slipknot to help hold the brakes tightly. Eventually, I found a nut and long skinny bolt (I think it was from a light fixture) that I could use to pinch the brakes together while I worked. This made adjusting the brakes on my Penn-Speed a breeze.
My second bike’s brakes didn’t drop below the rims, so connecting them with a bolt was not an option. I honestly can’t remember all the tricks I tried, but I think sweat and maybe a few tears were my go-to resources. Just yesterday, it was time to adjust my brakes once more. While trying to think of ways to hold the brakes together, I had the epiphany that my goal wasn’t necessarily to hold the brakes, but to raise the cable yoke (which I have also seen referred to as a cable bridge). This opened up my options. I started to imagine a compression spring that could fit between the wheel and yoke to force it up… Or something ridiculous along those lines. In my case, there was an arm for a reflector just under the yoke, which was the perfect space to slide in a socket.
Sliding the socket into this space forced the yoke up and held the brakes in place as I tightened the cable. I bumped the socket a couple times and sent it flying, but it was the most success I’ve had adjusting the brakes on this bike by myself.
Another technique I’ve used, though I am not sure anyone recommends this, is to loosen the barrel adjuster almost all the way before tightening the brakes. This allows me to tighten them up significantly afterward. But, I’m just a technologist.