Who knows the theory of 4 link suspension

[setecastronomy]

During the last days I asked advices on how to relocate the links of my tlt-1.
I was looking for some theory too, but it seems that most people use their rule of thumb.
K.B. suggested:

The rule of thumb for links is to triangulate them like on the Bender chassis, just as you said, and keep the upper and lower links parrallel

Anyway there are some after market chassis where the lower and upper links projected on a vertical plane are not
parallel. Most of the times they diverge towards the axle. I cannot figure out which is the expected behaviour.
In touring cars there is a geometric rule based on the suspension arms to determine the roll center and there are ways to make it closer to the baricenter for better stability. With a 4 link suspension how can I determine the roll center and how can I make it higher ?

After searching in many forums the only thing people agree is that it is a good idea to move the lower links for having better cleareance behind the axle.

[joesbruiser]

You may be able to find some helpfull info in this thread..
Anti Squat and Suspension Tech

[Big Mike]

I'll just pass on what I've found in the course of rebuilding my linkages 4 or 5 times.
One of the first obvious performance enhancements that I saw on a TLT was moving the lower link mount points from the bottom of the axle where they hung up on every little thing, to up in front out of the way. It was easy to move the shock mount points and free up a spot in front of the axle for the lower link mounts. But doing that alone triangulated the link geometry - they were closer together at the axle than at the chassis. It seized up the suspension, the articulation was cut in half. No good. I had to move the upper link mounts as well to bring the links parrallel with each other again. Back to the bandsaw and drill press for a new pair of servo plates, then the suspension was free to move smoothly again.
So far I can pass this along - the closer to parrallel the links are (horizontal view) the smoother things articulate. Triangulating one set of links from a vertical view will cut down on the flex-steering effect. Most guys mount the upper links at the axle close together behind the servo, like I have. Most 1:1 crawlers and monster trucks are the same. Some guys triangulate the upper links in the chassis. Depends on what chassis you run primarily. Personally I'm still working with the stock TLT chassis for now, and triangulating the upper links right behind the servos as close together as you can get them in the center seems to work best for me.

[setecastronomy]

Thank you for your suggestions Big Mike.
You say you are still using the stock chassis, as I'm.
How did you solve the big problem of the very high center of gravity ?
I think you use the stock tranny, with the heavy motor in a very high position compared with other after market chassis. And where do you put the battery ? On the front servo as many others do ?
What about twist (torque roll) ? With your link relocation is it less pronounced than in stock configuration ?

Thanks
Filippo

[Kamikaze]

I have always built my 4 links with the uppers triangulated and level with the ground at ride height, and the lowers triangulated opposite and angled down. I have zero axle steer and the suspension works great.

[Reflection]

I like to double triangulate my links,it gives less axle steer at full twist. On allot of 2.2's though,theres not enough twist there to really benifit from it.

Honestly,I think it helps in some spots to triangulate the lowers in at the chassis. It'll create a skinnier drag path to get hung up on. It might only be a tiny difference,but sometimes the tiniest difference is what wins

Heres the way I have my links set up and it seems to work well for me. It is on a super but could be scaled down to a 2.2 if needed.