It is my understanding that a radial tracking arm will be tangent to the grooves at two points on the disc surface, and that this is true of both straight and curved arms. Or have we overcome the laws of physics? Doug Pomeroy POMEROY AUDIO Audio Restoration & Mastering Services Transfers of metal parts, lacquers, shellac and vinyl discs & tapes. 193 Baltic St Brooklyn, NY 11201-6173 (718) 855-2650 [log in to unmask]