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True 3-link rear suspension

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I think the only sheet metal I'll need to... relocate, will be the front most part of the spare tire tub in the trunk. A bar all the way to the main hoop would be way longer than needed, I'm just looking to match the LCA length for minimal pinion angle changes. I'm also thinking about slotting at least one of the mounts with a serrated block for real fine tune adjustments.
You really can't have any of the links too long, IMO. Model it out in Suspension Analyzer. Is the SN95 longer in this area than a Fox? On my old Fox CP car, I want to say the top link to the back of the main hoop was 22". Lowers are 18" IIRC. Going up near the main hoop allows an easy and strong way to make a sliding mount with infinite adjustability.
OK, let's start over..
This statement was what I was referencing
"I am going to a TA on my S197 just because I don't want to cut the car up and the stock 3 link is pretty compromised, but in my experience a true 3rd link is the way to go for adjustability and also opens up a bunch of options for upper links with springs, cushions, shocks, etc. to further tune forward bite."

now with regards to a 3 link on an SN95/New Edge
Most racing organization forbid piercing the floor pan with suspension links. Somewhere around here is a pic of an outstanding 3 link in an SN95, problem is/was the upper link had to come through the floor pan and connect to the roll structure.
Similar to this, but it had an adjustable bracket up front, which us why I suggested using a trailing arm for the 3rd link.
View attachment 72864
You can go down the rabbit hole of designing your own suspension, (and it's your car, do what you want) but you can also end up with so much frustration that it's no longer fun, unless you just like fabricating things and cutting them back off. I have done some of this, back in the 90s I designed and built my own kart chassis (basically one giant torsion bar) it was very rewarding, however, I would never in a million years want to do it again, I built 4 prototypes, (I used to bring a hacksaw and welder to the track) before I got it right. I really wouldn't wish that on anybody, especially since all the work has been done before, with the sn95 chassis.
The PM3L is a decent solution to the problem, I think some NASA guys are still running them, I would just run the truck (torque) arm and adjust on that, the mid 80 to early 2K Camaros used that system and it worked fine, They still use it in A Sedan.
I don't disagree about suspension design, it's a cliff. I added SLA to a Fox mustang back in the day and built an entire EM car from the ground up and both of those projects involved hours going back from the software to the shop and redesigning.

But in my experience, getting a live axle to work with a 3 link is easier. (but back to your point, not easy) One can map it all out and I did that the first time, but I learned you can get 98% there by just making all the links as long as possible, as adjustable as possible, make the lowers so they never go higher than parallel to the ground at full compression, the upper point down at 7-10 degrees and tune from there. I tweaked upper angles a little, and played with springs and rubbers in my sprung upper link but overall it was mostly hassle free and just worked. The 600whp EM car was able to sustain over 1g acceleration on course without traction control and be driveable when doing it.

That's all fluff and away from your point, which I mostly agree with. If I were doing a SN95, I'd buy a MM TA and be done but each their own.

DaveW
 
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Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
Thanks for all the input and opinions, I’m not doubting a torque arm is very robust option with great performance. I guess I should have gave a little insight into my life in my opening post, this is a project, a hobby more or less. I enjoy creating things and building custom stuff, so you’re right it won’t end with making my own suspension, but that’s kinda the point.
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
So after I finished the panhard install I pulled the rear end and scannned it. Here is my first stab at the axle mount design. I want it to be bolt on without hindering any maintenance and minimal trunk hacking but still has a good range of adjustments.

5B3361E4-116D-4EF9-A437-9BE8F0CAD62A.png

9CC6BDFF-0FD8-4AEB-A34A-BF5A481AE625.png
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
Above the rear end in that area is the spare tire tub which I’m fine with cutting and moving. At ride height the panhard mount is roughly centered with the diff cover, I think, should’ve taken a picture of that first. I also didn’t think about full droop interference, so I may need to change that. And I was going to make it a slot with serrated blocks to lock the height but those plates are high from the places I found, and with hacking the trunk there’s more room for adjustment at the axle than the front. I’m open for suggestions though, this is just my first draft.
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
Whipped up a Rev2 version with non-adjustable axle side. I'll throw the rear end back in the car this afternoon to check clearances with the panhard mount.

3 Link Axle mount view1_Rev2.jpg

3 Link Axle mount view2_Rev2.jpg

3 Link Axle mount view3_Rev2.jpg
 
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Above the rear end in that area is the spare tire tub which I’m fine with cutting and moving. At ride height the panhard mount is roughly centered with the diff cover, I think, should’ve taken a picture of that first. I also didn’t think about full droop interference, so I may need to change that. And I was going to make it a slot with serrated blocks to lock the height but those plates are high from the places I found, and with hacking the trunk there’s more room for adjustment at the axle than the front. I’m open for suggestions though, this is just my first draft.
I'm a big fan of the aluminum covers with the bearing girdles, but they get real tight on some PHB during suspension movement, that's why I mentioned that.
Looking good though.. there's always something to work around.. lol
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
The more information I read from Ron Sutton, I'm starting to think about an offset 3rd link now, but again need to check clearances with panhard mount.
I've looked through Speedway motors but everything I've found would require modification anyways, If I didnt have access to a waterjet at work I'd definitely be purchasing premade bracketry, but with the WJ its pretty quick and easy.
 
First time poster here, I have an 04 GT with the primary focus of AutoX, until I do some more upgrades and feel more comfortable with taking it to an actual track. I haven't ran the car but a few times but I consistently have issues with the rear suspension not allowing me to exit a turn under power, always lifts the inside rear. My current setup is pretty basic, as I don't have much money to throw at the car with everything else in life going on. I have H&R Race springs, tubular control arms with poly bushings (soon to be modified for heims on one end), MM CC plates, MM full length SFC's, SR Sway bars and racing seats with 5pt cage and harnesses to keep me from sliding all over, running 18x10s with 295s square setup. MM Panhard kit is on the FedEx truck as I type this.

I have done some research and cant find anyone that has converted the rear end to symmetric 3 link setup. I've seen the Steeda 5link kit but I'm not a fan of the upper link mounting to the side of the OE torque box, the evolution 3 link kit looks more like what I want but not a fan of their frame mount either, and I'm not sold on the PM3L. I also want something adjustable that doesn't hang down low like the Torque arm.

Is there a specific reason the upper link should be offset to the right or would a centered link offer more consistent Left/Right turning characteristics?
I'm currently targeting 65% antisquat for nominal position with adjustment means on both ends, is that a good target or should I go higher?

Once I get the Panhard installed I plan on cutting out the upper torque boxes to fab my upper frame mount, so I'm looking to get any advice I can from now until then.

thanks
-Randy

View attachment 72801

View attachment 72802

I don't have any direct information on going to a "true" 3 link in an SN 95, but a 3 link is a 3 link. If you are someone who likes to build things, then I say go for it. I believe a properly done 3 link is the best choice if you don't have any rule constraints on cutting up the car (or you dont mind cutting up the car)...

Here is a photo of my 66 when I was building it, you can see how high I went with the link tower and the upper link goes into the back seat area of the car. I've since cut the panhard off because i screwed up geometry wise , so the car now has a watts link *gasp*.

Offsetting the upper link counters the torque from the drivetrain and will help keep the tires evenly loaded under acceleration. Go look at the fastest modern day solid axle cars (TA cars) and you will see many running an offset 3 link. They run very long links too, the attachment point is up near the drivers seat, offset to the passenger side of the trans tunnel...

20190615_122154.jpg
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
After putting the rear end back in the car, there’s a lot more real estate above and behind the pumpkin than anywhere else (at full droop and ride height) so I’ll probably revisit my first design and tweak it some to maximize the bar length and maybe use a slot instead of the hole pattern, my only concern with the slot is the bar moving from my preset height with the cyclic loading since the bar won’t be level.

B77EFBCC-56A4-41BF-9BC3-0CA633B1A9D7.jpeg
 
I am not terribly impressed with Ron Sutton's actual knowledge of autocross improvement. He is good at selling himself though. Despite that, offset is not bad if you can fit it in the packaging.

Stock car stuff is the way to go, but STAY AWAY from that crap with the holes drilled in it and go sliding on at least one end of everything. Here is the front of the 3rd link on my old EM car.
.em. 3rd link front.jpg

Axle end

em rear end.jpg

That car was TA style, 40 inch lower arms, 3 inch upper and you sat in between them. The 3rd link was an old Coleman sprung unit.

Here is the PHB Axle end
em-phb.jpg

I started this car with the frame mount for the PHB with holes in it, then switched to a slider like on the front of the 3rd link.

Coleman Racing and LeftHander Chassis are pretty good sources of stock car stuff. Howe Racing also. No road race tax on stock car parts.

HTH

DaveW
 

racer47

Still winning after 30+ years
392
497
Exp. Type
W2W Racing
Exp. Level
20+ Years
SE WI
^^^ 100% agree about Sutton (and Coleman and Lefthander and Howe)
 
26
35
Exp. Type
Autocross
Exp. Level
3-5 Years
North Carolina
So after checking clearances I have created a hybrid of Rev1 and 2 to push the mount behind the diff and utilize a 3" slot for adjustment and the central support a piece of DOM instead of bent bracketry for easiest fabrication. This leaves about an inch from the 3link mount to the panhard mount and will give enough adjustment to just run a fixed front mount. Then I can make all the adjustments from a sheetmetal compartment inside the trunk. I think I'll try this route and if I have problems with the bar sliding in the slot, as it will only be held in place by the bolt torque, I'll just splurge and get some serrated plates to weld on. Again any feedback is welcome.

Good to know about Ron too, thanks. Due to the panhard mount an offset link mount would have less room than a centered, but its always an option for the future.

3 Link Axle mount view1_Rev3.jpg
 

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