I have some dia compa ac 500 brakes on an old road bike. While the calipers are installed on the bike, with everything tightened, I can move (rotate) the calipers side to side with my hand. I've already searched online and there seems to be a lot of different suggestions and opinions ranging from using loctite to the idea that the hole in the frame/fork is "compromised".
Here's a picture for reference (mine are not exactly identical): http://4.bp.blogspot.com/_rFnXZUx3BwQ/TFH3HR5jIhI/AAAAAAAABpI/_VXBnW0Yhdw/s1600/DSCF0446.jpg
The calipers are held to the frame/fork with a metal rod with threads, a (capped) nut that gets screwed in in the "front", and a piece of metal that screws on to rod in the “rear”. Tightening that front nut only seems to add friction between the callipers. So, for example, when I release the brakes, the callipers do not return to their original position. Tightening that piece of metal in the rear seems to make it more difficult for the callipers to move (rotate). I’ve tightened these rear pieces as much as I could.
I have no idea if these brakes have been assembled correctly. One had 2 washers between that front nut and the calipers, the other one didn’t. Are washers even necessary? Regardless, both calipers rotate can be rotated like I described before.
How is this problem normally solved?
I meant to describe some negative symptoms. Why is it a problem?
It's a problem because they get off center as you brake. You get one brake pad rubbing against the rim as you release the brakes. So in other words, they don't retract evenly. Ideally, I would want the brake calipers to be an even, fixed, distance from the rim (not loose).
I thought maybe it was an issue of friction. I disassembled one and greased it. I also put lube on the inside of the cable housing. This didn't help.
What might also be a problem is the length of the cable housing. In the front, the housing definitely causes the calipers to tend to one side.
It might also be an issue of unequal tension in the spring. I'm reluctant on bending it though.