Originally Posted by Retro Grouch
Nothing works 100% of the time. It sounds to me like you've already done all of the common fixes. If you are working with ProMax or Tektro brake arches, a $20.00 set of Shimano Alivios might do wonders. I hate cheap brakes.
The funny thing is, the tektros are about equivalent to ultegra level Shimanos (the tektro dual pivot roads that is). They are good value for the money. Stop knocking things just bcause they aren't "brand name".
I'm going to have to suggest that you pickup a cheapo set of pads anywhere and see if that fixes it. It may be the kool stop, however unlikely that may seem. The other cause could be loose bolts holding the pad, or the entire brake assembly itself. Have you also checked the rim for trueness?