Originally Posted by
DannoXYZ
You MUST hold the front of the centre-bolt in place while you tighten the back. You need to use a 13mm cone-wrench on the front to prevent it rotating while you tighten the nut in back. It's that very last 10-degrees of tightening in the back that spins the front.
The basic concept is right - you have to hold the brake in position while tightening the nut, or put the brake in position with a tightened nut.
Some brakes have flats on the front, like an older Campy, and some don't. Some of the ones that don't, like the Shimano 6207 (600 or Ultegra grade single pivots from the early '80s) are designed for an Allen key, and the old Weinmann sidepulls have an acorn nut and lockwasher on the front of the brake pivot stud. If these two are jammed together well without destroying either one, they can by used to hold the caliper in place, but with not as much torque as you can get if the brake was designed with a pivot bolt rather than a pivot stud.
With all these techniques the last bit of tightening does the most damage to the alignment.
Moral of the story: after you get them adjusted right, don't let anyone do you the favor of snugging down your bolts for you.