Thread: 4-Bar Help

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I'm trying to get my 4-bar installed and having problems (rookie & 1st attempt). Shouldn't the coilover be mounted vertically? Right now all the bars are equal length but the coilover is tilted back about 20 degrees. Should the mounting bolts for the bars be perpindicular to the ground at ride heigth? What am I doing wrong. Thanks for any input.

Your bar angles are wrong. Can you get another picture that shows the front mount, too? and maybe another from the back to show what angle the shocks are at from the rear....

Do these pics help? I still haven't tacked the coilover mounts or installed the panhard bar.

I'm curious who made the 4 bar kit? It appears from the photos that the bars are all wrong on the angles. Any setups I've installed for a street car the lower bar is parallel with the ground. On a drag race 4 bar set up, the bars are different lengths with the top bar being shorter but even then at the highest setting the lower bar is only a few degrees above parallel... I've always mouned my coilovers vertical, as viewed from the side and not more then 20 degrees in at the top as viewed from the rear... It looks like this setup would need either A. a lower front mount for the lower bar, or B. you will need a very deep C notch in your frame rail to move the rear end up enough to ge the bottom bar parallel with the ground...

I just don't see where that setup is going to give a good ride or decent handling.....

It's a Scott's Hot Rods 4-Bar. The instructions are terrible! They say to look ato pics in the directions, but there are none! I sent them an e-mail to try to get this thing set up correctly. Thanks for the input.

Remove the coilovers and put a floor jack under the pumpkin. Raise and lower the diff through the entire range of motion with an angle finder on the pinion. Find out if the pinion is changing angles appreciably through the range and also if the bars are moving nicely with no binding through the entire range of motion. At ride height and rest, the pinion needs to be parallel with the trans output shaft. It doesn't necessarily need to point at the output shaft, just be PARALLEL with it so that the u-joints will be properly phased with the negative and positive angles cancelling each other out. In other words, you wouldn't want the output shaft at a negative 3* and the pinion at negative something. If the trans shaft is negative 3*, then the pinion should be at positive 3* or somewhere close within 1*.

It has been my experience that angling the bottom bar up somewhat will help to plant the rear tires on acceleration. Draw a vertical line through the middle of the front tire and then draw a horizontal line at the center of gravity (about the same height as the camshaft in the motor) and make a "T" above the front tire, then draw a line through the "T" and intersect with the tire patch of the rear tire. The angle of that line would be the perfect angle for the bottom bar.

It doesn't matter if the coilovers are vertical or not. Depending on the angle, you will just need a stiffer spring on the shock to make up the difference. The more angle on the coilover, the less effective the spring on it will be because you will be using less of the spring (not compressing it all the way as you would if the coilover was installed vertically).

It looks like your shock is fully extended. Do not install the coilover that way. Remove the spring and compress the shock to 55% in plunge and 45% in rebound. That will be the installed height of the coilover.

There's a series of phots on Scott's site showing an installation.

http://www.scottshotrods.com/Cars/Fo...tall/Index.asp

http://www.scottshotrods.com/Cars/35...ssis/Index.asp

I have to say I've never seen a 4-bar with this design. It looks like a cross between a 4-bar and a 4-link.

We bought an IFS front end from Scotts, and the after sale support is almost non-existant. You are pretty much on your own to figure out how to make things work. Some of the parts we got were just wrong and we had to swap them out for the correct parts. It was supposedly a complete hub to hub setup, and yet some of the parts wouldn't line up.

I agree that your bars look somewhat unusual in their design.


Don

I got a response from Scott's and they said that it all looks correct. They said the coil over is designed to be at a 15-30 degree angle. I'm still confused if the lower bar needs to be parallel to ground at ride height.

As Jack pointed out, this is sort of a hybrid arrangement. It is technically a 4-link as opposed to a 4-bar because the angles of the two bars are not parallel to each other like they are on a 4-bar. You have no adjustments on the forward bar mounts, so you can't try different angles like you could with an adjustable 4-link. The intersection that the two bars make toward the front of the car is the instant center of the arrangement and where this imaginary point is in relation to the center of gravity of the car will determine the characteristics of the arrangement so far as how the car hooks. If this is a street-driven vehicle, I don't think it's gonna make two hoots worth of difference where the instant center is placed, so long as it isn't under the ground or 20 feet in the air.

I do think that the ride and handling will be pretty harsh with this arrangement because of the lack of compliant material at the mounting points. It was obviously designed for purposes other than a good ride on a street car/truck. The track bar shown in the links Jack gave is normally used only in drag racing. Street cars usually use a Panhard bar or triangulated links to control lateral diff movement.

I will be using a panhard bar and not the diagonal brace that is shown in the pics. I just talked to Scott's on the phone and they said that I do have it installed correctly. I wish I had found this site before buying it. There's a ton of info here. All I can hope for now is that the ride isn't terrible. It's going in a 59 Chevy 1/2 ton truck.

O.K., panhard bar. The shorter the bar is, the more it will want to yank the diff left to right as the diff moves through suspension movement and the more bind you will get in the mounting points of your 4-link. Make the bar as long as is humanly possible within the confines of packaging it to fit into the truck. Construct a bracket that welds to the diff and anchors the bar very close to the backing plate at the wheel. On the other end, construct a bracket that welds to the frame and positions the end of the bar as close as possible to the backing plate. At ride height, the mounting points of the bar left to right need to be level. Note that I didn't say the bar needs to be level, but that the mounting points of the bar need to be level. You can twist or bend the bar into a pretzel to clear other components, so long as the bubble on your level is at neutral when placed on the MOUNTING POINTS of the bar at the frame and diff. It will make little difference whether one or the other of the mounting points is a little ahead or behind the other to miss other components on the truck, so long as you don't carry it to extremes. Let me say this again, MAKE THE BAR AS LONG AS HUMANLY POSSIBLE.

Originally Posted by rcs72

I got a response from Scott's and they said that it all looks correct. They said the coil over is designed to be at a 15-30 degree angle. I'm still confused if the lower bar needs to be parallel to ground at ride height.

When they're taling angle of the coilover, they are more then likely talking about the angle as viewed from the rear, not from the side!!!!

I don't like panhard bars at all..... By design they move the rear end from side to side on bumps.... Why not a Watts linkage instead. But if you have to use the Panhard bar, then as Tech emphasized, make it long and the mount points level to minimize the deflection the bar creates. With coilovers and their limited travel it's not really a big problem, I guess. But in theory and application they are totally wrong.....

I also noticed that scotts pic showed air bags and not coil overs .........this may make all the difference in the world on how it rides..on a light truck install.....

I did send the side view pic to Scott's and they said it is fine mounting the coil over tilted back 20 degrees. They did tell me to cycle it to make sure theres is no binding. They have a lot of pics on there site with coil overs but none that really show if the coil over is tilted to the back. I really hope once it's installed it doesn't ride like sh*t.