setting up an adjustable front beam

[advinnie]

Hi all I have a adjustable front beam with two adjusters one on each tube. But what do they mean when the say you need to pre tension the beam does this mean that one adjuster should be up and the other down or should both adjusters be in the same position ie both up, down or in the middle? Cheers all

[Ol'fogasaurus]

There are three styles of adjusters I know of, AVIS (an example: http://www.mooreparts.com/store/product ... -King-Pin/ , Sway-a-way (an example: http://www.mooreparts.com/store/product ... -King-Pin/) and Wright (I couldn't find a picture but it you have a copy of Baja Bugs & Buggies by Jeff Hibbard on page 54 they show a picture) with the AVIS being the most common used for the street and as I understand it is the easiest to install.

(I think this is correct) With adjusters in your beam you can raise the front end, lower the front end or change the time that one or the other of the springs stacks come into full use. An example of the latter might be: with a jack under the beam and your wanting to lower the car and smooth out the suspension/ride at the same time you loosen both the upper and lower adjusters to the height you want the front end to sit at then tighten say the lower adjuster (remove the jack and cycle the suspension to be sure you have the ride height you want). Once you have the beam where you want it then jack the beam up again but a little higher then set the upper adjuster. Drive the car to check the ride. You may have to do this a couple of times to get it right.

At least four other things to know: one is that you can go too low/too much tilt and it may be hard to get the front end aligned. There are shims and longer bolts that go under the lower tube in the beam to allow alignment and two, you can get dropped spindles to lower the front end. Three: on BJ cars they now make some eccentrics that are drilled a bit different than stock to also help with alignment. Four, you may have to change the shock to shorter ones when lowering or longer if raising.

My advice is worth slightly less than you paid for it.

[Marc]

From the Henry Elfrink book "Volkswagen Technicak Manual" (1964):
"A progressive spring rate has been obtained by mounting the suspension control arms to the torsion bars at a slightly different angle which has the effect of preloading one torsion bar with respect to the other"

The angle is actually determined by the position of the torsion bar center anchor point in the beam tube, not by the relationship between the arm and the bar, but the principle's remains - the lower arms and bar carry more of the weight; in the "free" position (disconnected from the spindle and shock absorber) the lower arm has more angle than the upper. Look at the location of the center grub screws on a stock BJ beam, you'll see that the upper one points more downward than the lower. This is what you want to emulate with your adjusters. The method will vary depending upon what type of adjusters you have, your ride height and shock absorber length, but the ultimate goal is to end up with the lower torsion bar carrying more of the load than the upper.

On pre`60 cars the lower arm had 4° more angle than the upper; `60-`65 (with 8 leaves) changed the angle on the lower arm to reduce the preload to 2½°. `66-up balljoint front ends have 8½° more preload.

The below pictures are of the third (thankfully obsolete) type of adjuster, called the "Select-a-Drop". It doesn't affect the lower torsion bar at all, instead it just yanks on the upper one to angle it downward (this reduces the weight carried by the upper, which naturally means that the lower has to carry more). One problem with this setup is that the center section of the top tube is free to shift from side to side, which makes it impossible to have a stable camber setting...I call it "Select-a-Flop".

[advinnie]

When I got the car it had no front beam at all so I have nothing to compare this one to. The way ive set it up once it was on the car was to jack up the car pull down on the upper arm so the adjuster was at its highest point and lock it on then do the same to the lower one and yes both adjusters are in the same position and both adjuster screws are pointing in the same direction. Does this make sence? The type of adjusters i have are i believe Avis style.

[Ol'fogasaurus]

Thanks Marc for the clarificatioin, I reread what I wrote and it was lacking.

I have forgot about the select-a-drop; I had seen one recently but I did not know what it was, I just thought it was a home made conversion.

advinnie, do you have a BJ or a K&L beam?

[advinnie]

Ball joint mate whys that?

[Ol'fogasaurus]

Ball joint mate whys that?

Just curious mate. Two different styles of torsion bar front ends; on the street the BJ beam is probably simpler to work with but there is nothing wrong with the K&L either.

Lee

[Marc]

Because the shock absorbers limit the downward travel of the lower arms you may need to disconnect them in order to set the Avis adjuster at its "highest" setting (adjuster block as far up as it will go, limited only by the slot in the static part).

To preload the bars so that the top one carries less weight, the top adjuster may need to be reset with some load on the wheels. Unless you have access to the right kind of hoist it's hard to get under the front end and work with it resting on the tires. I have a couple of stout crates to put under the front tires when I need to do this. I then can set the upper adjuster where I want it by using a floorjack under the frame head to raise/lower the car as needed.

[Marc]

...I have forgot about the select-a-drop; I had seen one recently but I did not know what it was, I just thought it was a home made conversion....

They do look pretty crude, don't they? State of the art 45-50 years ago. That's a K&L beam in the photos, you can tell because the grub screws are towards the top of the beam tubes. The most creative use of one I've seen was done by John Kelly of Ghia Specialties before he left Seattle to semi-retirement on the coast. He rearranged the components to allow the use of an electric motor to turn the lead screw (via a gear-reduction system). The motor resided in the spare tire well and was controlled by a switch under the dash so the ride height could be adjusted on the fly. I'm suppose someone's done something similar using an airbag, too.


John and wife Carla are now innkeepers at a B&B on the coast (Moclips WA). He still has some copies available of his sheetmetal-working videos ("Custom Metal Bodywork" and "Tuck Shrinking") for $20 each. More about those here: http://allshops.org/cgi-bin/community/c ... 0138836765

Check out their Facebook page (and the "View Tower" that he built): https://www.facebook.com/pages/Gull-Win ... 05?sk=wall

[Steve Arndt]

Select a drop = stiff wagon ride.

I had avis on one car. They wear out, can slip, and are hard to adjust. The Sway A Way are much stronger and easier to adjust on a car with pre load like a baja.

[Ol'fogasaurus]

Select a drop = stiff wagon ride.

I had avis on one car. They wear out, can slip, and are hard to adjust. The Sway A Way are much stronger and easier to adjust on a car with pre load like a baja.

I agree with the opinions Steve made. I don't know about the Select a Drop but seeing pictures of it, Steve's opinion does sound about right. For overall longevity, the Sway-a-Way units are probably the strongest of the bunch of adjusters and will last longer. I started to document a BJ off-road beam build a while back and made a serious mistake in reading the instructions (13 through 15) and made a big Aw $#it!. My advice after doing the goof it to read the instruction very, very carefully many times then check off each step as you accomplish it. The instructions that come with the kit are not quite the same as the Sway-a-Way instructions; I would download the Sway-a-Way instruction (http://www.swayaway.net/joomla/images/I ... USTERS.pdf) and follow them. The first instruction should tell you that there could be a problem. After you have properly done one beam or goofed it up then you reread the instructions again then it all makes sense. I would also mark out the instructions that apply to K&L so you don't get confused.

[Marc]

The problem with the Select-a-Drop (besides the aforementioned random-camber issue) is that the further you lower the car the more load is carried by the lower spring stack - the upper stack is typically somewhere between going along for the ride and resisting the lower stack, so naturally when you go very low with them the ride approximates that of NO suspension.
Avis adjusters are basically the same as the stock Porsche 356 setup, and work just fine on a street vehicle - but they have no place off-road.

[Marc]

...I would also mark out the instructions that apply to K&L so you don't get confused...

Good idea. The Sway-a-Way design puts their adjustment bolt at 90° to the stock grubscrew position, and the latter is different between BJ and K&L beams. When I divorced my first wife and gave her a car, I included an "Idiot Book" but the only printing I could find was a later one that covered Type IVs. It was well worth my time to spend an hour or so with a black marker redacting all of the text that didn't apply to a Beetle!

[advinnie]

Hi all I have a front beam with avix adjusters on it but how do I set it up? By that I mean do I just position both adjusters at the same angle or not? I only ask due to the fact that I have heard that I need to pre tension one of the spring leave is this true if so do I per tension the upper or lower spring leaves?
Thanks for your help

[Marc]

I've merged your latest post with the thread you started on the subject last August - I thought that we had this covered back then. On a stock balljoint beam, the lower torsion bar stack carries slightly more of the load than the upper, accomplished by the lower grub screw position being slightly higher on the beam tube than the upper, so that the lower arms have 8½° more angle (from horizontal) than the upper arms.
When you lower the front end by reducing the angle of the arms, as all adjusters do, it changes the way that the suspension reacts when a bump is encountered. At stock ride height, the wheelbase actually gets shorter when the wheel starts going up which makes the wheel sort of "step over" the obstacle. The less initial angle on the arms, the less this effect...if you start out with the arms horizontal, the wheelbase needs to get longer as the wheel rises so the suspension actually resists movement - this is why lowered cars have a "stiffer" ride (unless the lowering is achieved without changing the control arm geometry, as with drop spindles, smaller tires, or "ladder-mounting" the entire beam).
Displacing the adjuster angles to emulate the stock arrangement can't overcome this problem, but it will help by not exacerbating it. The more you displace the angles the more of the front end weight gets carried by the lower stack so you don't want to get too extreme or it could be overstressed and break, so I'd recommend that you don't exceed 10-15° difference.