3 Link advice and opinions

[shmoov69]

Well, like the title says, I am looking for some GOOD advice on a set up for my 69. I have been wanting to put a 3 link in it for about 5-6 years now, but have not been able to let go of the car long enough to do it. My original plan was to copy a later model Camaro rear suspension. But now I see the kits that are being made and they make me wonder if the 3rd gen style would even work. I am not much into buying a kit (even if it is obviously far superior, and expensive!) if I can get something to work alot cheaper with the help of some friends.
I am wanting something that will work better than the leafs at the drag strip and still be able to rip corners. I know that a factory 3 link is not the best out there, but is it better than what I got? What are the drawbacks of copying a factory set up except with coil overs? using the front spring pockets for the lower control arm mounts and making some sort of torque arm to mount to the tranny cross member or something like that. I am no suspension guru, but don't know why it would not be better.
Please give me some feedback on this.
Thanks

[baz67]

Shmoove,

Search is your friend. I know the is a multipage discussion in the archives, forum at the bottom of the forum page. You will get alot of info out of it. You will not get exact dimentions on where everything needs to go. That would be up to you.

[PTAddict]

I think there are two reasons you haven't seen more torque arm style rears on first gens. First, the driveline tunnel is pretty narrow, so there isn't a lot of room to tuck a torque arm up inside the tunnel and still keep dual exhaust. This means low-mounting a torque arm under the driveshaft, which has ground clearance issues and means building a heavier arm since you don't have room to triangulate it for strength.

Second, the math for calculating instant centers for a torque arm is not as straightforward as for 3 or 4 trailing link suspensions, nor can it be as easily adjusted after install without messing up other suspension parameters.

That said, torque arm designs can work really well. They are the hot setup for corner-carving in the '79 and up Mustang crowd, for instance, and obviously they've been made to work pretty well in the 3rd and 4th gen Camaros as well. Some folks think the stock torque arms are too long for optimal instant center (Global West makes a shorter replacement, for instance). Also, the stock 3rd and 4th gen torque arms are weak sheet metal pieces, which is why you see so many companies making stronger tubular replacements.

If you wanted to adapt a late model torque arm style into your '69, you'd need a torque arm (an aftermarket or fabricated one), a rear end with torque arm mounts (not a stock 3rd/4th gen one, they're very weak), lower control arms (you could mount them in the stock leaf spring pockets, make sure they are level with the ground as a starting point), a Panhard bar and mount (once again, stock 3rd/4th gen Panhard needs to be replaced for strength and adjustability), and coil overs and coil over mounts. Then figure out how to route exhaust (maybe go with a single large pipe like the 4th gens).

Looking at that list, it does not look like either a cheap or easy install to me. Particularly when you look at the price for a Quadralink or Lateral Dynamics 3-link, which are guaranteed to have far more thought put into the engineering and geometry than almost any backyard effort.

[Randy67]

Shmoov69,
Look at the torque arms being used on 79-up Mustangs. You can look at: http://www.maximummotorsports.com/ or http://www.griggsracing.com/ for how they do it. Their torque arms are mounted under the differential. It might be an easier way to do a torque arm without using the 3/4 gen t/a.

[shmoov69]

I had looked at the archives the other night and saw a lot of discussion about it, but did not see anything about a copy of the 3/4th gen style. It all seemed to be with a shorter upper link and hacking the floorboard and changing the rear seat. But I may have missed something in there, alot of read!
I am not too worried about the fabbing of stuff, and I think that we can make it for prolly around $500 or so, but I just do not know about the whole idea of copying that style of system. I can't seem to find the exact price for the LD piece. Anyone know the websites for them or the quadralink stuff.
Any more advice?
Thanks again guys!

[Matt@RFR]

Jimmy, our 3-Link kits are $3370. No website yet, but any information that will be on the website, we will happily hand out here too.

Mark can better answer your questions concerning following the late model suspension designs, but he's on his way out to Texas tommorow to do an install and won't be back until Wednesday 2/8. I'm surprised Dennis or Vince hasn't hopped in this thread yet.

Concerning your $500 goal: It obviously depends on how you're going to do the suspension, but I think you're way low. If you buy new link ends, be they rod ends or good bushings, and you run a Watt's, you're looking at $300-$400 or higher JUST for link ends.

[PTAddict]

The Maximum Motorsports or Griggs T/A might be a way to do a semi-budget T/A. Get a complete Mustang 8.8 rear from a boneyard (cheap and strong), then get a MM or griggs T/A kit and adapt/refabricate the front T/A mount, and fab your own trailing links. I would not fabricate my own torque arm unless I had access to a CAD program with FEA. T/As take extremely high bending loads and must be very carefully analyzed from a structural engineering standpoint to ensure they don't fail. And if you overbuild them, they become even heavier and add even more unsprung weight, which is the biggest fundamental issue with the T/A in the first place.

I made a post in the advanced technical discussion area about how to calculate the anti-squat for a torque arm setup, but I worked that out on my own and wouldn't use those calculations until others here review them.

[trayb]

Matt, What do your 3 link kits include?

[sinned]

I figured with all the discussion this topic has had over the years I'd let this one find its way to a past link. I will chime in with this however; a 3-link is the best way to go IF you don't mind doing the sheet metal work inside the cabin to accommodate it. There is no factory 3-link DIY or junkyard way to go here. You are going to have to fab it from scratch or (plug for my buddy) buy one of the well built, over designed, purpose built 3-link kits from Lateral Dynamics. You won't be disappointed with Marks kit or Matt’s skill, and depending on what your time is worth to you it may be cheaper to buy the kit.


I like T/A arrangements, they simply don’t have the adjustability I would like, if you decide you need to dial back the A/S a bit to accommodate for brake hop its not as simple as just moving a link up a notch.

[sinned]

And if you overbuild them, they become even heavier and add even more unsprung weight, which is the biggest fundamental issue with the T/A in the first place.

Even an overbuilt T/A still weighs much less than a pair of leak springs.

[PTAddict]

Even an overbuilt T/A still weighs much less than a pair of leak springs.

True enough, and the extra unsprung weight is concentrated at the center of the axle, which is better than having it at the ends.

[PTAddict]

I like T/A arrangements, they simply don’t have the adjustability I would like, if you decide you need to dial back the A/S a bit to accommodate for brake hop its not as simple as just moving a link up a notch.

I had always assumed the lack of adjustability to be true, as well. However, if my analysis in the advanced tech forum is correct, you could adjust AS in a torque arm setup by raising (more AS) or lowering (less AS) both the front and rear trailing link pivots at the same time. It's just that a TA setup doesn't lend itself to nice graphical constructions to determine the IC - at least I've not run across any examples.

[shmoov69]

Matt, how much of the floor needs to be hacked out and is it still no chance of having a stock back seat? I wasn't planning on doing a Watts linkage, it seems a little overkill for what I need. But I don't know! I am no suspension guy, I can tell you how to put a good roof on though!! LOL! I don't want some killer suspension that will knock the socks off of everything, just a good all around piece, if there ever was one! Heck, I may just put the leaf's back in it until I totaly re-do the car again. I have the fiberglass (composite) mono leafs from Vette-Brakes in it now and havent had much trouble, other than at the strip, it doesn't hook too well.
I will listen to all the advice that I can though! ; )
Thanks

[MrQuick]

I'm surprised Dennis or Vince hasn't hopped in this thread yet.

I was waiting for Den, he ain't got nother eles better to do. LOL

Wait a few months Jimmy.

[MuscleRodz]

a 3 link at a minimum will require you to split the back seat or possibly eliminate it depending on design. If you don't want to cut that much of the car up, go buy DSE's quadralink suspension. Next best think to a 3 link.

Mike

[sinned]

Actually Vince I made some progress today, swapped out those pathetic 750# springs and put the 950's in place. I also spent a couple hours with the air board and did some final 80 grit prep, it isn't going to win any shows but maybe Green Flag will let me on the track after a squirt of paint.

a 3 link at a minimum will require you to split the back seat or possibly eliminate it depending on design. If you don't want to cut that much of the car up, go buy DSE's quadralink suspension. Next best think to a 3 link.

Mike

Naaa, next best thing would be a T/A, then a Satchell, then a truck-arm, then maybe the DSE kit.

[Matt@RFR]

Matt, What do your 3 link kits include?

They include the front and rear crossmembers, a rear end of stock flange to flange width (add $200 for custom widths), C5 brake brackets, all the Watt's stuff and the control arms (your choice of rod ends on both ends or rod ends one one end and rubber bushings on the other). All hardware, a 30mm Craftsman socket for the bellcrank bolt, and an angle finder will also be included in the kits. The parts are sent out uncoated so you can paint or powdercoat to your liking, although we officially recommend either no coatings or strictly clear coatings for crack detection and maintanence purposes.

Coilovers, brakes and rear end guts will be supplied by you. There are too many choices and personal preferences out there for us to feel comfortable in offering these things in 'roller' kits. We are allready a dealer for Strange and a couple shock manufacturers, and we'll be looking into becoming a dealer for several more manufacturers to try and give our customers the best pricing that we can, but still retain all the best choices in hardware.

Matt, how much of the floor needs to be hacked out and is it still no chance of having a stock back seat?

See the attached picture. There is a fair amount of cutting, but none of it is any worse than, say, through-floor subframe connectors. It just looks worse. The first gen Camaro kit requires cutting of the trunk floor for the rear crossmember, but the second gen Camaro and the B-body Mopar kits don't. Also, the stock gas tank will work as-is.

And no, the stock back seat won't work with our kit. A later model style, split bun seat would. We've been toying with the idea of making a 'glass mold for our own back seat for each car that the customer can have upholstered and will bolt in using the stock attachment points.

I don't want some killer suspension that will knock the socks off of everything, just a good all around piece,

A good 3-Link, among some other designs, will do all of the above.

Mark and I are not here to push our kits on anybody. If a good set of leafs will work best for what your goals are, that's what we'll tell you.

With that said, I understand that suspensions designed for road race type cars are much like welding machines, in that the lesser models might do one thing acceptably, but the high end models will do ALL things very well.

[PTAddict]

Naaa, next best thing would be a T/A, then a Satchell, then a truck-arm, then maybe the DSE kit.[/color]

I'm assuming you're speaking purely hypothetically, based on the fact that the DSE is a 4-link design, since nobody to my knowledge is making T/A or Satchell kits. Yes, 4-links will have some amount of bushing and/or link deflection under roll, but the added roll stiffness from that deflection may or may not be negligible, depending on the details of the design. The Tuckers (DSE founders) were former GM suspension engineers, so they didn't just cobble together some multi-link design without understanding the basics.

I'd say, talk to the Tuckers and hear what design decisions they made and why, what are the basic parameters they chose for roll center, instant center, etc and why, how versatile is the design for various applications, what tradeoffs did they make for street vs. track, etc. In fact, I'll go so far as to say that anyone who picks a rear suspension without talking to them is making a mistake, even if you don't choose their product in the end. They are very thorough engineers, and their attention to detail in areas like quality control, durability, ease of installation and maintenance, etc is much greater than in most of the aftermarket.

I haven't had those discussions yet, so I wouldn't feel qualified to say for sure just how good the DSE kit is or isn't yet. The Lat dynamics is good, for sure, from a handling standpoint, and has the adjustability to be versatile. But it is obviously not the simplest to install, heim joints may not be the most durable on the street, etc. All depends on what you want.

[sinned]

I'm assuming you're speaking purely hypothetically, based on the fact that the DSE is a 4-link design, since nobody to my knowledge is making T/A or Satchell kits. Yes, 4-links will have some amount of bushing and/or link deflection under roll, but the added roll stiffness from that deflection may or may not be negligible, depending on the details of the design. The Tuckers (DSE founders) were former GM suspension engineers, so they didn't just cobble together some multi-link design without understanding the basics.

Actually I meant if you were going to build your own suspension, that would be the order of ideal design theroy in my opinion.

You did mean Kyle and the Tuckers, correct. I didn't think his wife worked as a design engineer for GM, and did Kyle work for GM in engineering? I know Mark did but didn't realize Kyle did as well.

[PTAddict]

Both Tuckers (Kyle and Stacy) were GM engineers involved in suspension design, production, and testing. I just went to their site looking for confirmation of this, and found this link on the front page:

http://www.stewartcomponents.com/cgi...002/000231.htm