Joined: Jun 2013
Posts: 4,094
Likes: 2
From: Bozeman
Bikes: 199? Landshark Roadshark, 198? Mondonico Diamond, 1987 Panasonic DX-5000, 1987 Bianchi Limited, Univega... Chrome..., 1989 Schwinn Woodlands, Motobecane USA Record, Raleigh Tokul 2
Hit the wheels with some rubbing alcohol and LIGHTLY touch with a scotch bright pad.
The black marks from the pads changes the friction coefficient and makes the brakes pulse. My guess is that the black mark is hiding an "unsmooth" spot.
If that's not the case, make sure the brakes are toed in correctly.