<VV> Another Brake Question

[Roger Gault]

This weekend I rebuilt my '65 convertable's brakes.  Now they have this weird "flutter" to them.  When I apply the brakes, I feel a high frequency (maybe 10-20 times the wheel rotation rate) vibration or flutter.  By the end of my 15 mile commute (mostly freeway), it's nearly gone, but it comes back the next time I drive it.

Work done:
  Replaced all 4 rubber brake lines
  Rebuilt wheel cylinders
  Replaced shoes
  Turned rear drums
  New front drums
  New right front wheel bearings
  Repacked left front wheel bearings
  Replaced the oval spring on the emergency brake reaction rod in left rear brake.
  Replaced emergency brake cable.
  Bled system

Did not:
  Check turned rear drums
  Sand surface of new front drums

So, smart guys, have you ever seen this before?  If it was grabbing, I'd think contaminated shoes.  If it was at wheel speed, I'd think warped drum.  But, as it is, I'm baffled.

Thanks,
  Roger

PS:  The new front drums have small fins on the outside, which I am concerned might be touching the wheels (stock 13"), but I was tired and hurrying when I put the wheels on and did not check.