Now that parts have arrived, I am able to start figuring out my rear suspension setup. I knew early on that I wanted to run a triangulated four link setup with coil over. The install and geometry looked simple enough until I started down the rabbit hole of research.
Now I am not going to try to teach you about tri four links I am just gonna document my experience figuring out and installing one. Maybe some of the links and info will be helpful to you or you can just laugh as I stumble my way through this.
First thing I came across was the free 4 link calculator online. This is super simple to use and gives you a really good idea of what your setup will be like when its installed in the truck and working.
https://www.crawlpedia.com/4_link_suspension.htm
This page gives you a lot of information about what you are trying to achieve when choosing the link locations of your mounts.
Here is the general set of rules that I tried to follow.
- 25% of your wheel height is your vertical axle link separation. (35″ tires = 8.75″ of vertical separation.)
- Lower Links should have no more than 10 degree slope.
- Upper links should shorter than your lower links (75% is recommended for road use, closer to even for off road use)
- at least 40 degrees of triangulation in either your upper or lower links.
Armed with the calculator, tape measure and enough knowledge to be dangerous I started to plot out my links. When I started this I had some vision in my head where the links would fall on the frame or at least how I wanted to on the frame. So I measured out those ideas.
My initial goal was 100% anti squat, research told me this was a good default starting point for most vehicles. Success… 100% AS
This didn’t look right to me so I went looking for help and found the Pirate 4×4 forums.
https://www.pirate4x4.com/forum/
Quickly signed up for an account and posted my results, with some quick replies my suspisions were confirmed and my upper links are longer than more lower links, causing all kinds of issues. Back to the drawing board.
Attempt number two after sleeping on it and figuring out how I would mount the lower links differently. So I straightened them out and stuffed them further up the frame. Looks like this should work.. 100% AS and uppers are shorter than the lower links. SUCCESS!!
Since the guys/gals over at pirate were so nice I thought I would post my new found success.
FAIL.. Roll axis angle of 5 would cause some interesting driving behavior, basically cause the truck to want to spin out, or at least that is what I have been told. I was told you want that closer to 0 or even -a few degrees. I also learned that 80-100 AS is totally acceptable and will be fine for my application.
So back to the drawing board.
Try number 4?5? did save pictures of all my attempts, but this attempt seems to check all the boxes,
Success! AS of 81%, -3 degrees on my Roll axis and Links are close to the same length but a bit shorter.
Now at this point I was getting a lot of help and someone pointed me to the updated calculators. So armed with an updated calculator I thought I would take another attempt, with the same numbers to make sure it would work.
New calculator has a bunch more settings and more visuals that you can see what your truck layout will look like.
This is when I realized I was entering some of my numbers in correctly, I was entering the full horizontal separation for the links vs half which the calculator was asking for, no big deal I would just cut them in half, seemed all my AS/RA stayed the same… success!!… no so fast. Now I don’t have enough triangulation in the links to keep the rear end centered.
Ok back to measuring and another attemp.
This was easy enough to solve as I knew what by this point what each number would do to the calculation as I moved them around.
So finally landed on what will be my starting point for mounting my Tri 4 Link in the truck.
I had to order a few new brackets as the ones I had would not support the mounting locations I need to use now. I also going to have to fabricated a mounting point on the frame that currently doesn’t exist but extending part of the kick ups in the rear Z of the frame.
That was far too much head scratching.. but at least I have a good starting point. Time to weld some stuff into place.. WHAT COULD GO WRONG?
TWO GREAT VIDEOS I FOUND: