I would like to hear others opinions on this subject. I came across this pic of a guys 4-link on IG, and I commented on it saying that I thought the rod ends should be parallel to the rear end because of the pivot point. he then proceeded to get very upset, posting a very long rant about how I was "insulting" his abilities. I've had this same discussion with friends that have done some 4-links, and we seem to be divided on the subject. I would just like to hear what you guys think and why? I (personally) think the rod ends should be parallel to the rear end or you'll get "roll bind", what do you think? And please, don't get upset over this.
What you are shown is more or less a triangular 4 bar,,it;s been around for years in one way or another. We are more familiar with the parallel 4 bar because they were/are more popular with the Street Rodders. HRP
Triangulated 4 link. Very common - many Chevy's used a version and so did 10 Zillion Fox body Mustangs. You can find them under chassis from some of the biggest names, like Morrison, Detroit Speed. Global West, Heidt's, and on and On
May be had to see but this is a 32 frame we used the same basic style triangular setup for my friend Dave's Deuce pickup. HRP
here's a pic of my 4-link, all of my rod ends are parallel, the first pic he has his rod ends at an angle to the pivot point
I think he's asking for opinions on whether the rod end pair centerlines should be co-axial, and that axis should be parallel to the axle's transverse centerline. I've often wondered the same thing, but the reality is I don't think it matters much. Bob
You will have "roll bind" with end parallel, too. Mock it up, then run the rear up over a bump on one side. Thing is, "roll bind" is not a concern, as the rods themselves will twist enough and the ends compress enough to make it a non-issue. Cosmo
I see what you're referring to, but major car mfrs all seem to design links with the ends perpendicular to the run of the bar. Recall the angular four bars on street rods: they had 12 degree ends for attachment to '32-'34 frames, mainly for aesthetics. (I've seen them attached to angular spuds with straight ends, too) Any 'roll' or 'travel' bind incurred might be in an extreme angle, (such as the excessive heights raised and lowered to on lowriders, frame layers, 'donks', etc.) Interesting question. Geometrically 'fused'...
From Chassis Engineering by Herb Adams; http://www.amazon.com/Chassis-Engineering-Building-Performance-Handling/dp/1557880557: the bars need to be angled toward the roll center for anti-squat & roll steer. the way you have it in the first photo is correct.
Theres going to be binding regardless from body roll, but (to me) it seems that putting them at an angle, they're already going to be binding, and body roll will just add more. I may be completely wrong about this, but putting them parallel makes more since to me.
The pivot point of the rear of the car is the "center" of the diff. If you run the bars parallel with the frame, it will bind as the rods would need to compress & extend during body roll. That would be impossible with those massive rods
It looks to me that they will bind either way whether theyre angled or not, if you think of how an axle goes over a bump it will bind in either set up. Correct me if im wrong but theres a tonne of cars out there with a working and correctly handling triangulated 4 bar system with rods perpendicular to the axle.
you understand what I'm saying, they both will bind with body roll. my 4-link has absolutely no binding with up and down travel, with body roll the bushings are flexing slightly, you'll get that with any setup unless you're using hemi joints, but when the rod ends are not parallel to the rear end, there is flexing with simple up and down travel, then body roll would just add more flexing. And this might be a useless debate, the flexing might be so minuscule that it will never be a problem,
Waaaay more info then you prob ever wanted to know or care about on a four link. Easy enough to toss one in, but to understand the geometry of one and the effects the angle/length/position of each link plays takes a bit. Granted, this is an OT site and some of the info isn't relative, but getting the anti-squat set and other misc will be relavant http://www.pirate4x4.com/forum/gene...-version-my-4-link-analyzer-request-help.html
OEM's and aftermarket suppliers have been building triangulated four links for decades. The OEM's use rubber bushings, which allow a lot of compliance, the aftermarket guys generally use urethane bushings, which are stiffer but still offer some "squish". Spherical rod ends won't bind, as they allow motion in more that one plane, bushings will compress as required. The geometry of the links and locations of the pickup points are far more critical than the bushing material. If you just roll a rear axle under the car and weld the link brackets wherever they touch, you run a good chance of ending up with an evil handling car. Even with a live rear axle (as opposed to IRS), you need to learn about roll centre, roll steer, and anti squat. Research is required.
By mounting your bushings parallel with the rear axle, you're asking the small thrust shoulder of the bushings to absorb all the lateral weight transfer when you turn a corner. By angling the bushing, much of that lateral load is taken by the 'barrel' of the bushing.
There needs to be something that gives. A suspension that only allows movement in 1 plane would work only if the axles were free to move in & out (like with an independent suspension). Since that is impossible with a standard axle, the suspension arms need to have that ability.
Just goes to show that Henry Ford had a better way with the wishbone suspension. One pivot point with no bind.
i just ordered a 4 link from pete and jakes, i talked to them on the phone.. (some old guy i did not catch his name) but he said he has been building hot rod chassis for 40 years and the major difference from triangle to parallel 4 link is that a parallel puts more power to the ground and has to have a panhard bar. triangle dose not need a panhard bar and works just fine for a hot rod. so unless your building a drag car triangle is a good fit so thats that im running. as for those pix of sideweeler, im going to have to agree with everyone that just does not seem right, im not saying it wont work but if it worked that great you would see everyone selling there 4 links like that.
I chime in here. [ here is an abbreviated answer with out getting too deep ] The triangulated 4 link [ or a 3 link ] will NOT bind if designed correctly. By “correctly” I mean No solid bushings, so there is some form of torsional and lateral compliance in the links [ eg: ball-joints ] If you look at the above pic the uppers which are triangulated together will have an instant centre further forward of the arms [ you need to draw an imaginary point of intersection of these arms ] This is where the body roll-will pivot from.[ roll centre or roll axis when in conjunction with the front ] If you can imagine this [viewed from behind] as a pivot point at the upper centre of the rear-end housing. The whole rear end arcs from this pivot point during body-roll. Now lets look at the side links from a sideways view. During body-roll one link arcs upwards and forward and the other link arcs downward and forward [I'll use parallel links for an example ]. So during body-roll there will be an upward pinion angle correction [ from static ] If the triangulated links are below the rear end [ pointed either forward or backward ] the roll centre is lower and the pinion angle changes in a downward direction. With shorter upper links [parallel from a side view] you get downward pinion angle change during “squat”, and the more the rear squats down the closer the instant centre moves towards the rear. The shorter instant centre behaves similar to a shorter ladder bar, so the torque reaction at the pinion acts like “anti-squat” fighting the weight transfer during acceleration
i think you guys are getting away from the original question. here is a pic of a different setup, (not 4-link), notice how all the rod ends are parallel to the rear end? my question is... why do you not put the rod ends parallel to the rear end on a triangulated 4-link?
One reason to stay close to known reasonable settings is that anti-squat in the rear unloads the axle during braking and can cause wheel hop (See NASCAR on road course), the first time this happens in an emergency is not the time to learn about it. Oh, I agree, I wouldn't want to load the upper mounts sideways or in shear. They take the place of the panhard bar and need to oriented 90 degrees to their load path. Since they are at about 40 degrees angle, and lateral loads approach centerline loads you could make a case for orienting the bushings 90 to the axle, car makers figured this out a long time ago Triangulated 4 links are an economical and proven moderate performance compromise, they are not the top of the rear suspension food chain but do a "pretty good" job. jm2c Hoop
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