Triangulated 4-Bar or 4-bar with watts-linkage?
 

Help me!!!
Which setup works best for roadrace use? I have ladderbars with
coilovers and a panhard bar now. So i guess i´ll stick to the coilovers and rebuild the rest, but which typ of suspension works best?

3-link, since you starting from scratch why have you limited your options to 2 of the lesser ideal designs for that application? Satchell, 3-link, T/A, and truck arm are more ideal than the 4-link or C4L.

Ok, do you have any pictures or know where i can find pics of that typ of setup?
Btw thanx :thumbsup:

from doing my own research and asking about a million questions about the same thing. It turns out that the good stuff is pretty expensive. I myself just decided to stay with leaf springs from hotchkis but I will be bringing them inward a bit and relocate my shocks. Not exactly the best set up but a good ride for handling and driving. Plus the whole thing with shocks cost under $600 not bad when you consider that a 3 link will cost about 3grand and you are more likly going to have to use a 9inch rear.

I would agree with this except for the truck-arm choice. I suppose the best question to ask is how do you plan on using your car? Track only, street only, occasional track day, cruiser, racer?? :)

Also, how much are you willing to cut up on your car and of course, your budget.

Do a search for "3-link" and/or "lateral dynamics"

There will also be a suspension story on all the types in the upcomming April issue of PHR (the next issue to come out in about 4 weeks)

I have looked into the Lateral Dynamics setup and it looks
awesome :thumbsup:
Abit expensive though. I have to look into this a bit
more before i make up my mind. The car will meet both
street and road race course.

The direct answer to your question is a parallel four link with a panhard bar.

Here's an example:

http://www.detroitspeed.com/QUADRALink10.html

Maybe you could explain the advantage of a PHR over the triangulated upper links?

Also, why would a PHR be more advantageous than a Watt's link?

Knowledge is power :)

4-link
 

win the 4-link set up in the giving away and you are money ahead. :willy: :willy: :willy: :eek:

Triangulated upper links are a version of the satchell link rear. The angled links should preferably be below the rear for several reasons. One, with the angled links on top, they are usually very short and will bind with very little movement. if they are on bottom they are much longer and less likely to bind. You can cure some of the bind with the use of Jonny Joints. the second reason I have been told is with the angled links on bottom, it lowers roll center height but not sure why. Dennis or Marcus can answer that.

Panhard Bars are better for packaging around exhaust systems. Watt's links are better centering devices for the rear in that they don't allow the rear to move side to side at all. Panhards with enough travel move in a an arc which is side movement. Disadvantage of Watt's is getting the exhaust out the rear effectively. Hope this helps and if I am wrong on anything please correct me. I am a young grass hopper still in training. :lol:

Mike

You and me both.. I learn something everytime I discuss this.

So if the angled bars were moved to the bottom then what would control the rotation of the differential?? (pinion angle)

Ok, I had a long old response typed up it was “lost”. Here is the abridged version. Converging the lower links is known as a Satchell link and is totally different than C4L the Chevelle and Mustang use. The Satchell link has a much lower RRCH due to the converging link that define the roll center being located below the axle rather that above it.

The only advantage to using a PHB over a Watts link is packaging. A frame mounted Watts link allows RRCH to remain constant through range of motion and has a lower unsprung weight.

Steve, the Satchell link controls pinion movement the same way a C4L does; through use of the the parellel links and somewhat through the angled links.

Gotcha, thought he meant move the triangulated upper links to the bottom.. lol.. that had me perplexed :)

As Dennis said, a true Satchell has the converging links on the bottom. Most if not all the factory converging links are on the top and are very short and is done for packaging and are bad about binding. If they are on the bottom, the converging links can be much longer and less affected by binding through normal suspension movement.

Mike

Rear suspension systems can be tricky little devils, and as usual, the "devil" is in the details.

The roll center of any stick axle suspension depends upon what is controlling the lateral movement of the axle assembly, preventing actually (lateral being side to side, not to be snoot about things). It is a pretty hard thing to describe, it depends entirely upon the given geometry of a particular system. They all work differently, but let's tackle the two in the title.

A parallel four link (or three link, or torque arm setup with parallel links for that matter) depends "entirely" upon the Panhard Bar, or Watt's linkage to resist axle movement in the lateral direction, i.e. under cornering forces. IN this case, the roll center is defined by the intersection of the PHB height (keeping things as simple as possible) with the centerline of the axle, and again, to make things simple, let's assume that the links are parallel in top (plan) view. The roll center is an imaginary point in space that the car will roll about, specifically, the sprung mass of the car, under a given lateral acceleration (cornering force), and it is a very important attribute for certain. More important than where it "is" in a static case (not moving, just sittin' on the curb), at least in my opinion is what it does dynamically. PHB's do a really nice job at controlling the roll center in a dynamic sense, the other "better" solution is a frame mounted Watt's linkage, as Den' mentioned.

A converging four link does things a bit differently. IN this case, the angled arms (usually on the top, as in GM A body, late Mustang, plenty of aftermarket setups), not only control the pinion angle, but they are also responsible for controlling lateral axle movement. To find the roll center of these setups, you need to look at the convergence angle and intersection, and frankly, without a picture, it is really hard to describe. In the case of the GM A body, and also the Mustang (and the derivitives of thes in the aftermarket), they suffer from a really high static roll center, and worse, the roll center moves all over the place. Not only that, but think about it, the upper arms are asked to do two different things at the same time. I am personally not too good at multi-tasking, and these setups aren't in usual practice either. If you have ever driven a later Mustang in anger, there is no question that the back end of the car has come around on you in an abrupt fashion, known as snap oversteer. This occurs when (and because) the upper arms fully compress their suspension bushings, and the system becomes rigid (a trait of ALL four link systems in roll, by the way), and not at the time you'd like.

The Satchell setup is essentially a GM A-Body turned upside down, and it can be made to work pretty darned good. The engineer that designed it is named, get this, Terry "Satchell." It's far better than the other type, because the roll center height is a lot lower, but frankly, it suffers the same binding issues as the other four link systems. It's a bear to package too, the long upper links need to go somewhere, and that means no back seat.

So what do you do? For a street car? Whatever you want, and just do a good job tuning it. They will all work pretty good if you aren't nutso about the last ounce of performance. What's the ultimate solution? There isn't one, it ALL depends upon what you want in terms of packaging, performance, cost, ease of install, tune-ability, appearance, etc.

What would I buy? You're joking, right? :unibrow:
M