3-link rear suspension torque arm questions

[Stg1Regal]

Done some looking into a 3-link torquearm suspension,like what I see, but I had a couple of questions.

If my car, a G-body ( 82 Regal),dosn't have a kit out on the market for this set up, how does one determine the correct torque arm length?

And for that matter, where to mount the front pivot point.

I know a Watts link will be needed and seen the one from Marcus at SC&C and will likely go that route.

The reason for my asking is... seen over at the BMR website the big plate mounted to the rear of the diff,then covered with a Diff cover, and all the torque arm mount points were incorporated into that, wonder if possible that idea and design one myself, or found one of DENNIS KIRBANS replicated GNX diff covers and design a torque arm off it.

Any way shape or form a decent front mount is required, all the nes I seen, seem to mount near or around the trans out put area or even on the trans crossmember itself.

I have one of the CROSSMEMBERS.COM dual hump cross members, maybe thats a good spot.

Are there any good suspension websites to go too, to determine the length and geometry of the 3-link?

Again thanks ahead of time

[GrabberGT]

Good questions. I think I'll tag along to see what answers you get.

[wendell]

Are you trying to build a torque arm or a three link?

[parsonsj]

I know a Watts link will be needed and seen the one from Marcus at SC&C and will likely go that route.Marcus makes awesome stuff, and you can't go wrong there. I question the need for a Watts link... why not a panhard bar? They work just fine, are lighter, and are easier to fabricate.

Just a thought.

Oh, and what Wendell said. Which is it: a torque arm or a 3 link?

jp

[GrabberGT]

Any way shape or form a decent front mount is required, all the nes I seen, seem to mount near or around the trans out put area or even on the trans crossmember itself.



I assumed Torque Arm based upon the above statement. RRS calls their Mustang Torque Arm system a 3-link oddly enough.

[Randy67]

The GNX torque arm is one idea. Another is to undersling the arm like the Mustang uses, which gets around having to modify the driveshaft tunnel for more room (depending on torque arm length). It doesn't require a special cover for the axle. Just tossing out ideas.....

[Norm Peterson]

The GNX/Kirban device isn't really a torque arm, since the chassis side is fixed in place by a pin. That makes it a lot more like a centrally mounted single ladder bar. I don't think you have much option with where to locate the forward pinned pivot with this arrangement without having to use a few big, soft bushings or else you'll likely create an argument between it and the LCAs.

I have seen a couple of "real 3-link" approaches for these cars, either of which could be made to work. Centrally mounted off the existing pumpkin UCA "ears", or off a pedestal mounted to the passenger side axle tube. Think Factory Five Cobra replica or "right side upper of Steeda's so-called 5-link for Mustangs" for the pedestal type.

As badly as the current Mustang's rather short upper link has been "evaluated", the whole business works better than the converging/triangulated 4-link that was in the previous generation of that car.


If you really want a true torque arm, I suggest that you start by deciding on how much anti-squat (and anti-lift under braking) that you want. That answer, combined with ground clearance and sheetmetal location (and your willingness to modify same) will probably narrow down the choices somewhat, even if you aren't sure where you want the IC to end up.


Norm

[Stg1Regal]

Thanks for the response guys....

Grabber GT
Thats right the same set up is called both names, 3-link or a Torque arm...pending on who you talk to.
The idea is/was to elimanate my upper control arms, very close in the designs of the BMR FABRACATION'S kit for the 67-69 F-Body Camaro or Firebird and RRS's Kit for the Vintage Mustangs (wich I have seen in person ..verry impressive set up)

Randy67
Yep the GNX set up wasn't the best, but knowing it worked with that rear cover was my thoughts for the rest of the set up.
But as mentioned, it wontbe a good idea because of the driveshaft tunnel modificationsthat are needed to run the arm to the front mounting point, so yes a underslung design would be the best, simular to MAXIMUM MOTORSPORTS design for the SN95 80's-90's Mustangs.

NormPeterson
Your right that 3-link for the mustang,with the upper mounted third link does work well.
Still trying to grasp the terms "anti-squat" and "anti-lift",seen those used on several websites wich was selling their 3-links.


Now the fun stuff...

I did get a chance to speak with Marcus from SC&C, that a 3-link works very well when coupled with a Watts-Link set up, but in the confines of a GM G-body metric chassis,there just isnt the room to benifit from it with out adecent amount of work fitting it in.

Now thats not saying it won't work.

Marcus has built one for a G-body test mule a while back and it works very well, and it suited for more road course racing , but can be streetable, but took some decent amount of mods to make it work, plus its a caged car and is running his top of the line front suspension, and some very sticky and big tires in all 4 corners.

So being a budget bolt in .......well talk to him...

But alas.....not to fear as of now using his test car and watching the SN95 Mustangs race road courses he discovered the Watts link set up, and those stangs were doing very good, for just that Watts Link,.

So he designed one fo the G-bodies, and they work well in our " real world" fun driving habits.
And he stated pretty much as good as the 3-link he designed, but has its limits, but most of us wont being driving that extreme everyday.

As for the rest if one wants to build a 3-link for a vehicle chassis that dosnt have kit already for it, according to Marcus, the torque arm should be long as possible and mounted securley to a, lets say the trans crossmember.

Again I dont see why a underslung design couldn't be used.

again thanks ....and those are my thoughts and gained info

[Norm Peterson]

Still trying to grasp the terms "anti-squat" and "anti-lift",seen those used on several websites wich was selling their 3-links.
Squat is what the rear of the car with rear springs of any sort does naturally as load (not weight) is transferred rearward during acceleration. Lift is the same kind of thing that happens back there during braking as load is transferred forward.

"Anti's" are geometric effects of the suspension that oppose these movements (and in extreme configurations can actually make the movement go the "other" way). IOW, some of the load transfer is taken through the suspension linkage rather than through the springs, and since the springs wouldn't be gaining (or losing) as much load, they don't compress or extend as far as they would in the absence of these geometric effects. At 100% A/S, none of the load transfers through the rear springs, and there is no squat at all. How to calculate the percentage is presented in several books (there's a list around here somewhere), and while the percentage at static ride height is not the whole story, knowing roughly what it is (and/or what you'd like it to be) will get you going off in the right direction.



Marcus has built one for a G-body test mule a while back and it works very well, and it suited for more road course racing , but can be streetable, but took some decent amount of mods to make it work, plus its a caged car and is running his top of the line front suspension, and some very sticky and big tires in all 4 corners.
I'd seen the prototype bits for that, and have been wondering ever since what had happened or was going to happen with it. Knowing a little about Evolution Motorsports similar design for the earlier Mustang, I'm wondering what the problem was, as the EVM product did appear to be bolt-on. Sadly, EVM recently had to close their doors, so it may be a little more difficult to find out what they generally did. Link (http://forums.corner-carvers.com/showthread.php?t=40472)


Again I dont see why a underslung design couldn't be used.
The Mustang versions have it a little easier in that the 8.8" axle has some sort of weight bolted up to it that simplifies the axle side attachment a bit. There have also been some Mustang designs that were/are, for lack of a better word, scary (even after redesign). Without having a picture in front of me, I don't see why you couldn't build a low torque arm that attaches to the GNX/Kirban diff cover. Their own traction arm already has a tube that goes underneath, so I don't see much reason you couldn't run it pretty much straight once you got it past the diff itself. But to get the strength without making the TA beam deep, you'll probably end up heavy.


Norm