I am building up a bike for my wife and last night I began brake and brake cable installation. I installed Shimano 105 dual pivot brakes onto the frame and fork, but I am curious about centering the brakes over the rims.
Front wheel as an example: I snug the nut holding the front brake, eyeball the spacing on between left and right brake pads and rim, and tighten the nut. Then I installed the front brake housing and cable. When I turn the handlebars 90 degrees in each direction, to see if I have a proper length of housing, the force of the brake housing pushes the brakes out of center. Thinking that I do not have the nut attaching the brakes to the fork tight enough I get out the torque wrench and set it to 87 in-lbs (Shimano specs 69 - 87 in-lbs) and find that I have already tightened the nut past 87 in-lbs.
It seems to me that a lock washer or even rubber washer between the brake assembly and mounting point on the fork would go a long way in preventing the brakes from spinning so easily but no such pieces came with the brakes.
What am I missing here? Suggestions?