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Help needed setting up 4-link

4K views 21 replies 7 participants last post by  aosborn 
#1 ·
I am needing some help setup a 4 link on my 51 ford car i was wondering if anyone on here has done a 4 link, when setting this up should i put the springs in place and measure the distance from the axle to the front of the springs? then use that same location as a mounting spot for the 4 link? i know i just need to do it to make sure everything is square but i just want to make sure when i lower the car that the rear end does not shift one way real far and give the wheels a akward look in the wheel well, Thanks
 
#4 ·
Frame set-up on 4 link rear end

From your post I gathered that you are planning on having this subframe idea set-up to drag the frame on the ground at the low ride position..

The important thing to remember when doing this is that center pivot point on a 4link is not the axle center or the center of the wheel, but the center pivot point on them is the point where the lower trailing arm attaches to the rear frame. The best way to understand the way the wheel will be positioned into the wheel opening at different heights is to use a homemade guage. The gauge should be a length of anything (length of wood, or steel) that is indexed for the mount at the frame and the center of the rear axle. Install the gauge over the mounting bolt for the trailing arm at the point where it mounts onto the frame..... The idea here is to make this gauge act as a compass would, to swing the arc, as you simulate the action of the wheel going up and down in the opening. Doing this will demonstrate that as the wheel travels up and down in the wheel opening, it also moves front and back in the opening.

Understanding these dynamics will make the job turn out much better. Of course with these extreme modifications a perfect positioning will be difficult at every ride height, but work with the idea of a best case scenario to reach your goal.
 
#5 ·
Are you buying a 4 link or a 4 bar, (when the terms are used correctly, they are different ), or making your own?

If you are using a 4 link, with unequal length bars, the approximate center point of the axle swing is at an imaginary point forward of the bars, where an imaginary line drawn through the center of the pivot points converge, and where the axle winds up at any point in is arc it is very dependent on the length and position of the bars in the brackets...(4 links have axle and frame brackets with multiple holes, which allow you to move the rod ends up or down on the brackets to change the anti squat characteristics of you car on launch)

If you are using a set of equal length parallel 4 bars, the pivot position of the rod ends is fixed at the axle and frame, and the axle swings in an arc centered on the midpoint between the upper and lower forward pivot points..it creates a parallelogram as it swings up and down

Either way, it is best to mock up the suspension you are using with the axle and wheels to see where the wheel looks best at the ride height you like. Tack weld the stuff together and jack the car, (or axle), up and down to see where things wind up. If you can, set the bars so they angle down towards the back at ride height... that will give a better ride, and minimize the distance the axle moves forward as it travels upwards. A good rule of thumb is to aim them at the centerline of the crankshaft, at the back of the motor..

If you are making your own bars, the longer the length, the less the axle will move forward when it moves up.

I don't know what year car you are working on, but most post WWII fender openings are not exactly round, so you can cheat some on location. Pre war stuff is really easy to see a wheel in the wrong place. I usually mock up the wheel in the center of the wheel opening at ride height, when it's dropped the tire is up inside of the wheel opening and it is harder to see the lack of concentricity between the wheel and opening.

That's how I do that stuff, it takes longer but WYSIWYG when you are done.

Later, mikey
 
#7 ·
fast68 said:
ive got an uncovered 4 link custom built and narrowed 9" rear setup that was on the 69 fairlane out here i can takepics of it

if you want pics to see how its done, to give you ideas, etc

yes please




and i bought a universal triangulated 4 link kit from sucide doors, i am getting alot of ideas so keep them coming
 
#9 ·
If your looking at dropping it on the ground,You will be better off with the 4 bar set up.. :)And your universal triangulated 4 link kit..Your talking about.Is really a triangulated 4 bar.Don't know why they call it a universal triangulated 4 link kit. Like Mikey said they are not the same... :nono:
 
#18 ·
low50s said:
ok now what about them twisting when i air out, i just dont want them binding
If you set it up right..you shouldn't have any trouble with it binding.They are on alot of cars with air bags. :) Look at a lot of pictures of that set up.It will come to you.Look at more then one . :)
 
#22 ·
In an airbag setup, I would recommend a parallel four bar and a watts link instead of a triangulated system. And I would recommend installing as long of bars as possible. Set it up as described earlier with the bars level at your main ride height. By using long bars, the wheelbase will be altered less through suspension travel than using short bars, and with a parallel set-up, you won't have pinion angle change like you would with the triangulated system. You can either set your wheelbase at ride height, fully compressed, or somewhere in between, it is really up to you.

Andy
 
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