Norm Peterson
Corner Barstool Sitter
The '79 GM intermediates used a very similar triangulated 4-link roll-bind arrangement, and I didn't tell the whole bushing-mod story for that car before. After doing the length and cone tweaks, I drilled into the bushing faces in the same general regions as the voids in the WL bushing pictured above. First shot was with a small drill bit, maybe 1/8". Way too much lateral head-toss on bumps and dips taken at an angle, so I made them a lot bigger (forget how much). Huge reduction in head toss, meaning huge reduction in unintended roll stiffness/bind. I think I figured it was at least 80% reduction.Hear, hear! I've been a long time opponent of poly bushings in the trailing arms. SN95 'quadra-bind' was my first concern with them.
Ditto for the 3 link/panhard S197. I wouldn't put poly in any of it except for the panhard, which shouldn't need to twist much. I remember getting a fair amount of push-back on the subject, until poly failure in the upper and lower became more common. I used to think the poly-balls should be okay, but it seems they might have designed them with too much pre-load on the bushings. I'd only use heim joints (edit: or del-sphere) or rubber bushings in any of the trailing arms.
The S197 does benefit from its LCAs being (almost) parallel to the chassis centerline, so providing one spherical joint eliminates most of the requirement for off-axis compliance in the bushing at the other end. Use of the word 'most' is intentional.
Maximum Motorsport came up with a 3-piece poly bushing arrangement for the Fox/SN95 that was similarly intended. Were you on Corner-Carvers back in the SN95/New Edge days?
Norm