Calling on Triangulated 4 Link Experts - Need some advise Please !

[waid786]

I am building a street rod and I want to use Ford Explorer 8.8 axle with triangulated 4 link setup which my chassis will require. Since the center housing is cast iron, I will have to weld the mounts on the tubes which will force me to use very short upper links which are about 9 inch from eye to eye and are same size as 1994-2004 Mustangs. See attached picture.

If I use Mustang size upper shorter links, do I need to use same size lower longer links which are mounted straight?

How would the suspension geometry change with longer than stock lower links (extra long) are used ?



Thank you

[raustinss]

No you don't have to use the same length arms. Example GM A bodies 64-72 . Now as to the geometry, that's out of my league . I can tell you there's some relatively easy math to figuring out what length and where to mount them would be best ,unfortunately I no longer have the calculations book marked . Sorry. I'll try to find them again , maybe in the mean time someone else can jump in here and help

[waid786]

I building a street rod like this one with this frame. I just want to make sure there is no binding or do some funny things!

Thanks

[waid786]

I went to salvage yard today and took measurements. The Mustang's rear axle upper smaller control arms are about 9" center to center and the bottom are about 18" center to center.

For my project, with Explorer 8.8, my upper control arms will be same size as Mustang about 9" center to center. However, the bottom will be about 24" center to center.

Would this cause any issues?

For reference, here is a picture of Mustang 8.8.

Thanks

[Alwhite00]

Could you put the upper links outboard on the axles and the center mount on the frame?

[waid786]

Could you put the upper links outboard on the axles and the center mount on the frame?

The frame drops down and there is no brace for me to mount to. When I was at the salvage yard, I saw that the older Mustang had triangulated 4 link and the new Mustang had the 3 link with a panhard bar. What was interesting was both the 4 link and the 3 link had the smaller control arm about 9 inch and the longer control arm was about 18 inch or double the size.

[slammed68]

I went to salvage yard today and took measurements. The Mustang's rear axle upper smaller control arms are about 9" center to center and the bottom are about 18" center to center.

For my project, with Explorer 8.8, my upper control arms will be same size as Mustang about 9" center to center. However, the bottom will be about 24" center to center.

Would this cause any issues?

For reference, here is a picture of Mustang 8.8.

Thanks

I wouldn't say that having links that length would necessarily cause issues, but there's a lot more to it than just the length of the links. You need to account for mounting positions and a number of other factors. If you search around on the web you should be able to find a 4 link calculator without too much trouble.

For reference, the triangulated 4 link from ridetech for a first gen camaro has lower links around 26 inches long and upper links around 10 inches long. This is mostly due to packaging constraints and while it may not be optimal, it certainly works well.

[jetmech442]

Definitely not an expert, but I have a few comments that may help. The longer you can make the upper arm, the less pinion angle change you will experience as the axle moves up and down. If the truck is already tight and not doing a lot of travel, that becomes less important. The Side View Angle (SVA) on the A bodies is like,8 inches or so. Using factory geometry pretty much ensures that your okay in this area.

The other variable to consider is antisquat. The pic looks more of a street truck, so dialing in launch or corner exit stuff is probly not an important factor. The only area I could see it causing a weird issue is if the value AS value is high, like 150-200%. This will cause the rearend to raise significantly every time you hit the gas. Driving like that gets old after a few miles.

I initially had the cutlass dropped in the rear with springs AND had the edelbrock anti hop relocation mounts installed(cause I didn't know any better), I think the AS value was in the 200% range if I recall, and touching the gas would cause the rear end to lift(planting the tires really hard), but it made even street driving nearly impossible.

If the lower arms are horizontal, then the uppers will need to angle down. How much down? If you get measurements we can plot it and help out.

Hope this was helpful.

[bikefreak600]

pretty much as said above, the longer the links the less pinion change you get. I would pay attention to antisquat and try to get it close to 100% as possible since you have a fresh starting point. have you considered using multi hole frame brackets & axle brackets ? that could be the difference in making it handle well vs having a poor ride. personally i would ditch the triangulated 4 link and do a 3 link with watts or panhard.. but thats me lol

[waid786]

It been a while since I posted my original post. I received the frame I ordered and will be using 1994-1998 Mustang 8.8 axle which is already setup for multi-link instead of Explorer 8.8. Due to my application, my upper link is going to about 22" inch long and will point little bit down. The bottom link is going to be about 25". I did some mock up with flimsy BMW link and will have it made using 1" DOM tubing. In the picture, the axle is sitting at 0 degree pinion angle and at ride height.

Is there any issues with long upper link that actually point down ?

Waid

[jetmech442]

Nope. no problem at all with top links pointing down, almost all point down to some degree(or top/bottom pure horizontal. Those are some nice long arms man, good stuff. Good idea with he DOM, in your tri 4 those upper arms are responsible for absorbing those bending loads when the truck is cornering so you definitely want some beef in them.

If you want to take a few measurements, we can tell you about where the antisquat should be. If not, no worries, just know that the more you point your arms down the more antisquat you will have.

One more thing, the lower control arm angle directly effects stability in turns. If the axle side pickups are lower (arm angled down towards the rear of truck), then in a turn the axle "self steer" towards the outside of the corner. This can be good for a car wanting to make tight turns, but may feel twitchy at high speeds. The opposite is true if the pickup is higher, not as responsive in slow corners but more stable in fast corners. And again, maybe take all this with a grain of salt. I tend to tinker and tune a lot to get it to feel just the way I want, others just learn to drive the car as it is and that also works well. generally, if the car isn't near extremes then it will drive just fine.

if you want AS, we need:
Camshaft height:
Wheel base:
Height of lower control arm pickup point on axle:
Height of lower control arm pickup point on frame:
Height of upper control arm pickup point on axle:
Height of upper control arm pickup point on frame( or just the angle it is pointing down):

[waid786]

jetmech442,

I will not have the final numbers until I get the tri 4 link kit. This guy on eBay will make me a custom tri 4 link kit to fit my truck using 1" DOM for $275. I am not too crazy about all of the poly bushings but the upper axle bushing will be factory rubber to cushion the driveline little bit. Once I have everything I will let you know.


https://www.ebay.com/itm/USA-MADE-We...MAAOxyzGlQ7t~J

[dontlifttoshift]

The frame side of the lower link should (almost) never be lower than the axle side.

In this case, with all the bars running downhill towards the frame mounts, the car will squat everytime you pick up the throttle. Leaving a stop light - squat. Every. Time.

Strongly recommend picking up herb Adams book, Chassis Engineering. It is not expensive and covers enough information to build a decent understanding of the most basic principles to build a decent hot rod.