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True 3-link rear suspension

racer47

Still winning after 30+ years
375
455
Exp. Type
W2W Racing
Exp. Level
20+ Years
SE WI
Sutton isn't necessarily wrong (or right). He's just a slimy used car salesman kind of guy that always has ulterior motives that will make him money.

The mount looks good. The slot mount won't slip. 1000's of racecars have slotted suspension mounts that don't slip.

Those extra curves on the forward mount that follow the case shape aren't doing anything for strength. It will only be as strong as the narrowest section. Other than that, I think its a good design.
 
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5,219
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...


View attachment 73016
FWIW that would need to be boxed in most racing sanctioning bodies. This has been the rub in the SN95/Foxbody platform for years, in order to make all the links work, you have to pierce the floor pan. Then when you do, you, if it is allowed within the rules, it may not be allowed by the safety regs, then, if you can slide it by, you have to climb in the trunk to adjust it, because there is no access from the passenger compartment. This is why developing a workable 3 or 4 link has been such a PITA.
 
4,622
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Just for fun, is there any way you can run links from the axle tube to the chassis at the end of the axle and just get away from farting around with that mid section completely?
You're basically doing a back half anyway.
1646315960501.png
 
19
27
Exp. Type
Autocross
Exp. Level
3-5 Years
Gibsonville NC
Just for fun, is there any way you can run links from the axle tube to the chassis at the end of the axle and just get away from farting around with that mid section completely?
You're basically doing a back half anyway.
View attachment 73039
I looked into that but the panhard mount is pretty intrusive, the upper links would have to be significantly shorter. But given the OE uppers are ~8" shorter than the lowers it probably isn't that big of a deal, just more components.
 
19
27
Exp. Type
Autocross
Exp. Level
3-5 Years
Gibsonville NC
Sutton isn't necessarily wrong (or right). He's just a slimy used car salesman kind of guy that always has ulterior motives that will make him money.

The mount looks good. The slot mount won't slip. 1000's of racecars have slotted suspension mounts that don't slip.

Those extra curves on the forward mount that follow the case shape aren't doing anything for strength. It will only be as strong as the narrowest section. Other than that, I think its a good design.
Thanks, I really just got a little carried away with the anti-rotation mount, I was going to have cutouts inside that maintained the same width as the top narrow part mainly just for the ascetics when all these people flock to look under my car lol, *sarcasm*
 
99
156
Exp. Type
HPDE
Exp. Level
Under 3 Years
Michigan
I love the idea of a properly executed 3 link in a SN95. I started on the design of my own and had visions of a girdle like the one you've designed as well. Nice job on that 3D CAD, btw. I'm too busy to design and fabricate a new rear suspension for the Mustang for now, so I went with an extremely reasonable short term solution- MM Torque Arm. If I keep this car as a track toy for long enough I'll eventually do the fabricated 3 link. But for now, even with it's limitations, it will not be the weak link in the car...I'll take that title ;).

The offset third link is the way to go. It cancels some [or all, depending on how far it is offset] of the torque steer, so the car will behave in a more consistent manner on both right and left hand corner exits. I'm fabricating a tube chassis for my '69 Falcon, and my upper link is offset 8" [7-12% of the track width is the equation]. I had a conversation with Mark Magers from Lateral Dynamics about the effects on roll behavior, he had this to say:

"8" is very close to our offset, great for packaging, and extremely small left/right roll impact to the point where it is negligible - of course, using good engineering principles in regards to link lengths, etc."

When I started the restomod process on my Falcon I decided to go full tube chassis. I began studying suspension design, kinematics, and vehicle dynamics. I gathered a lot of information from Ron Sutton's posts on other forums, great information there. And a lot from other sources. The main thing I landed on was, because we can get close by approximating COG height, F/R location, etc, but it's not exact, building in enough adjustment to be able to tune it in. Plus you'll want the adjustability for different tracks and uses.

All in all, I love the idea, man, if you've got the time and ability to do it. As others have said, you'll definitely want to tie the upper link connection points to the roll cage or some other reinforcement structure. But I think you're headed in a good direction here. Keep us updated!

Brad
 
19
27
Exp. Type
Autocross
Exp. Level
3-5 Years
Gibsonville NC
Hopefully soon I’ll be able to update this, I was finally able to weld the rear mount together but haven’t had a chance to bolt it all on and throw the rear end back under the car for mock up. House projects have taken priority over the car for right now.
 
62
120
Exp. Type
W2W Racing
Exp. Level
10-20 Years
Los Angeles
Dude, that's the mount from hell..
How does it keep from rotating on the old bushing mounts?
That looks like some overkill!

The CAD had a link that went down to the bolt hole near the pinion that was for the NVH weights for rotation, looks like it is one side only now.

From guesstimating the size of the side plate that thing will take 40,000lbs of load, how much horsepower are you making? :D😂 Good for 10g of acceleration!

Pretty cool though, glad your developing and not just bolting on!

Don
 
19
27
Exp. Type
Autocross
Exp. Level
3-5 Years
Gibsonville NC
Yea it’s a little overkill but I didn’t bother gauging up my suspension and measuring stress to run CAE so I just made everything thick to not worry about it. Correct, the rotation is controlled by the long mount running to where the weight was mounted.
 
19
27
Exp. Type
Autocross
Exp. Level
3-5 Years
Gibsonville NC
I guess I'll update this to not leave people wondering. By the time I got around to starting to cut off the torque boxes it had become so swampy miserable hot outside that I just decided to push this off until its cooler or I get AC in my garage/shop. Thankfully I started hacking the drivers side box off and hadn't touched the passenger side so I just threw a spherical in the rear end housing and a double adjustable upper link with spherical on the chassis side as well to run the PM3L for now. Hopefully this setup performs well so I can actually make some events instead of my car sitting on jack stands all year.
 
85
90
Exp. Type
Autocross
Exp. Level
5-10 Years
Virginia
A PM3L works pretty well too. I ran one for awhile and there are plenty of road race cars that run them. At least until cooler weather. Seat time > car modifications

My current garage has AC/Heat and insulated, let me tell you it was a game changer.
 
86
89
Exp. Type
HPDE
Exp. Level
10-20 Years
San Jose
FWIW that would need to be boxed in most racing sanctioning bodies. This has been the rub in the SN95/Foxbody platform for years, in order to make all the links work, you have to pierce the floor pan. Then when you do, you, if it is allowed within the rules, it may not be allowed by the safety regs, then, if you can slide it by, you have to climb in the trunk to adjust it, because there is no access from the passenger compartment. This is why developing a workable 3 or 4 link has been such a PITA.
What would need to be boxed?
 

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