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S197 rear LCA Torque Box bolt hole ovaled

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Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
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 '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.

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
 
If you look at the close-up of one end, you'll see that the bushing is contoured such that there is a little flexibility against twist-direction rotation of the LCA itself and little or maybe no bushing material as long as the sleeve. The intent is to add some flexibility in at least one direction without compromising stiffness in the direction(s) that you want relatively high stiffness.

While I don't know anything about WL's material itself, it is an example of voided-bushing technology (normally an OE-level tactic). Just at the aftermarket level rather than OE, which if you look at the OE Ford LCAs you'll see something similar at work. Ford and Whiteline probably feel that some additional compliance needed to be designed into the bushing shape because neither of them are using any spherical at all.

Incidentally, these inner sleeves really aren't 'crush sleeves' in the same sense as crush sleeves used for pinion preload in a differential. I'd defy anybody on the planet to actually manage to crush or collapse an aftermarket bushing's inner sleeve.


Norm

Thank you. I think I'm going to go with these. You had mentioned earlier that the load was supposed to be borne by the sleeve, not the bolt, and this is one of the few aftermarket solutions that does that without going to a metal joint or BMR style, where a fluted poly bushing rotates around a sleeve aided only by grease. I've heard too many stories of the BMR style creaking and I think a metal joint would be too extreme for my application.

Cheers everyone.
 

Grant 302

basic and well known psychic
Were you on Corner-Carvers back in the SN95/New Edge days?
No, I was a drag racer back then. No road courses back in Hawaii, although I was hooked back in the late '80s and early '90s when I visited my brother here in SoCal.

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.

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.

Wow. Sounds like *you* should have been advising a suspension parts manufacturer. Agreed on the use of 'most'. I think they're okay to use if replaced as a regularly scheduled maintenance item. Your modifications would go a long way towards making them last longer, less prone to failure on track, and perform better.

Thank you. I think I'm going to go with these. You had mentioned earlier that the load was supposed to be borne by the sleeve, not the bolt, and this is one of the few aftermarket solutions that does that without going to a metal joint or BMR style, where a fluted poly bushing rotates around a sleeve aided only by grease. I've heard too many stories of the BMR style creaking and I think a metal joint would be too extreme for my application.

Cheers everyone.

I think that's a good choice, but certainly want to hear your opinions. I have the Eibach ones with a similar bushing and they've worked pretty well for dual-duty and are quiet on the street. I've has them on since late 2014. Not as tight as I want for the track, but pretty good compromise for how I use my GT.
 
No, I was a drag racer back then. No road courses back in Hawaii, although I was hooked back in the late '80s and early '90s when I visited my brother here in SoCal.



Wow. Sounds like *you* should have been advising a suspension parts manufacturer. Agreed on the use of 'most'. I think they're okay to use if replaced as a regularly scheduled maintenance item. Your modifications would go a long way towards making them last longer, less prone to failure on track, and perform better.



I think that's a good choice, but certainly want to hear your opinions. I have the Eibach ones with a similar bushing and they've worked pretty well for dual-duty and are quiet on the street. I've has them on since late 2014. Not as tight as I want for the track, but pretty good compromise for how I use my GT.
I couldn't find non adjustable eibachs, and at nearly stock height, i couldn't justify doubling the cost of the whitelines for adjustable lcas. I will keep you all posted once I get these on. My car should be a pretty good test for street longevity and durability.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

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