Hi everyone I was wondering what angle to set up the bars on a triangulated 4-bar? Any info would be great. Dennis.
yes im kind of wondering the same question, im curently setting up a 4 link on my 51 ford so i will be following this thread closely
45* is optimum for stability and articulation. More creates binding in the bushings, Less decreases articulation, meaning roll binding. Anything between maybe 30* and 45* will work ok. Less becomes a "why bother" question and more would just be bad.
Would someone please explain to me how a triangulated 4 bar rear suspension set-up with poly type bushings can ever work without binding? What I mean is, the upper bars are trying to move through opposing arcs. Detroit allowed for this by having very flexible bushings in the bars/arms but when a poly bushing is used it has to be binding and trying to tear itself apart. The more suspension movement the worse the binding would have to be.
You're paying attention. The only way such a setup would not bind at all is with spherical bushings or by canting the bushings perpendicular to the arc of travel. You sometimes see this on bagged truck suspensions. In the real world, the binding or rather deflection, required in this setup is minor due to the limited suspension travel. Knowing it's there makes it all the more important to avoid adding to the problem.
I went to Thorbeck Brothers (www.suicidedoors.com). They make a rod end called a pivot bearing. It has enough flex to handle the deflection without binding. Much smoother operation than normal poly bushings.
Bearings will ride harsher but will relieve any potential bind. Polyurethane is not really suited for bushings as it has no torsional shear and they are not a good solution for suspension - this is why Detroit used rubber with a metal shell insert which has rotational and torsional shear. Urethane rides harsher than rubber as well. As suspension guru Herb Adams said about urethane " It looks good on the shelf in the parts store". I would always opt for bearings rather than bushings that bind - but maybe that just comes from race car experience.
this is the kit that i bought http://www.suicidedoors.com/4-link-.../heavy-duty-universal-triangulated-4-link-kit i wonder if i should have gotten the super pivot, when your talking about setting things up at 45* are you talking about the bars going from the center section going out to the frame? so i got the 2 bars going directly under the frame, then from the center section out, but if i "air out" im woried about the driveshaft angle changing binding the driveshaft, or do you put that into account when your setting up the rear end angles ?
Being an old circle track builder/Driver I also agree with the heim joint over the pretty bushings. Looking at the picture for reference the lower bars need another tube brace on top. Not knowing what HP this is going in it may be right for this particular installation but better built lowers would go into any thing I built.
I used a 5.0 mustang 8.8 rear, hung bars on the factory ears and made brackets to weld onto my chassis where the bars fell. I did not use factory type bars because I went with coil overs. My upper bars are bushed with factory rubber and lowers are poly.
I just got finished with my triangulated 4 bar and was thinking the same thing about the binding then I was thinking that since the one side of the bar is welded to the joint and the other end is the adjustment with the locking nut, why not just leave the locking nut loose. It cant unscrew as it is fixed on the rear housing and the front is a welded end to prevent turning. So why cant you just leave the adjusters loose? They will only turn about a 1/4 inch on a 360 circumference on a large amount of rear end travel and prevent the bind.
As far as the 45 degree angle for the top bars, I made a wooden buck to hold the top arms in place in relation to the center line of the rear end.
I am almost done with mine. The top bars are not quite 45 degrees apart. I used 3/4" hiem joints at every connection. I am using airbags in the rear and I have at least seven inches of travel with no noticeable change in pinion angle. Here are some really shitty mock up picture before the bags.
Another option for ends is the bushed ball. There are a number of makers. the Currie Johny Joint is a popular one. http://www.currieenterprises.com/cestore/johnnyjoints.aspx
I would think yes, replace them. I will most likely replace mine also but I'm a long way away from that point.
Dang thats what im afraid of, this project has nickle and dimed me, but it will be worth it in the end, i should have just ordered there super piviot from the begining, then i wouldnt have had to worry about this problem, i have to get my car out of the shop by may weather it my be finished or not so im just trying to get as much done in a short amount of time
+1 on this, stay away from heims on the street, these hybrid joints are the ticket. The factory used soft ruber bushings to deal with the bind, if you go solid urethane you will loose articulation (ride quality and road holding ability) What works on a drag car is not generally what you want on a street car.