Trailing arm alignment

[Bad Bob]

This is where I'm at with my IRS conversion. The trailing arm pivots are tacked for now. Do the single spring plates go inboard the trailing arm like this? This way seems to line up fine.[img]

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To get the camber adjusted before welding, my plan is to clock the spring plates about 3/8" off the lower stop, ( at the same angle ) and move the inner pivot bolt position up or down and place a level on the axle bearing surface. Should I set the level with a little positive camber to compensate for the arm twisting when the car is on its wheels? I'm sure someone has been down this road before.

[Bad Bob]

Or, has anybody made an adjustable pivot point?

[Jprather]

Hi Bob,

Good topic and perfect timing. I would also like to know more about the camber adjustment. I had a shop do the IRS conversion for me and the camber is different between the rear wheels. The shop just dismissed it and said I should not expect them to be the same. I have had the worst experiences with shops so I have decided to do my own work from now on.

I can't add much to this conversation but I will be following. Looking forward to what the forum has to add.

[Steve Arndt]

A jig is available for 100 bucks which will (should) put you at stock camber angle and make it equal on each side of the car.

For a baja that is jacked up high you have a good idea about changing the setting. When I started my project of lengthening some stock arms I set them close to the down stops like you mentioned. Then I welded the bearing housings in plumb (straight up). On a stock arm they would have had slight positive camber at this point in the range of travel of the arm/spring plate.

A similar game can be played with at the pivot point variable that I was doing with the bearing housing position on the arm.

You should tell us your intended use of the car. Is it road, road racing, offroad, etc. Those influence your ride height and the camber you end up with.

[Bad Bob]

Hey Steve, this is for a street car. I did use the jigs to tack the pivots, but measuring the axle bearing cup shows 1 deg. neg camber on the right and 1.5 on the left. This is with no load on the suspension. I suspect this is from the arms twisting over the last 45 years. the question is, how to adjust to end up with 0 deg. under load?

[Steve Arndt]

Are you positive your arms aren't bent, twisted, damaged?

Do you have it mocked up with urethane bushings at the spring plates? and the pivots?

There is more than 1 degree of adjustment built in. The scissor effect with bolt hole tolerance between the spring plate and trailing arm allows some rotation. This can be used to adjust them for camber. Try changing one arm one way and the other the opposite and you may be able to get them both just right right (at say 1.25, half way between 1 and 1.5).

At full droop you should be at slight POSITIVE camber. At full compression you should be negative. For street use aim for zero or just a touch of negative camber at ACTUAL ride height.

[Bad Bob]

I swapped the arms and now have positive camber. This is with rubber bushings. Since it's only 1 deg. positive, I'll leave them there and relocate the shock mounts.

[Steve Arndt]

Wheel alignment and some camber adjustment is available by scissor/shifting the angle between the trailing arm and spring plate at the 3 bolts. That is what I meant.

Switching arms side to side is usually done for extreme lowered cars where they have too much negative camber and it correct it back some. If you don't want it that lowered then I would try adjusting the camber with the arms in their normal position left and right.

[dd-ardvark]

QUOTE Or, has anybody made an adjustable pivot point

Yes is the answer. The IRS inside adjustable pivot I built gave 9 degrees positive to
negative 9 with no change in toe. I copied the porsche 911 one, no need in reinventing something.


David / dd-ardvark

[dd-ardvark]

Have a look at this..., this what your talking about?

http://s1356.photobucket.com/user/dd-ar ... ort=3&o=24

[Bad Bob]

David, that looks like the ticket. How much travel ( in inches) do those have?

[Jprather]

Wheel alignment and some camber adjustment is available by scissor/shifting the angle between the trailing arm and spring plate at the 3 bolts. That is what I meant.

Switching arms side to side is usually done for extreme lowered cars where they have too much negative camber and it correct it back some. If you don't want it that lowered then I would try adjusting the camber with the arms in their normal position left and right.

Steve,

Can you explained the scissor effect a little more? I am hoping that this may help me with my project. Thanks

[Jprather]

Never mind Steve. I searched for scissor and found the info. I hope this helps.

[Jprather]

In case anyone wants to know. Here is a pretty good thread on the scissor effect

http://www.shoptalkforums.com/viewtopic ... r#p1170069

[dd-ardvark]

Bad Bob, to your travel Q. - It gives 3” of movement or 1.5” from center up and down. This is where I got the neg. 9 degrees to pos. 9 out of the chamber adjustably.
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Have a look at this Porsche 911 inside adjustable pivot.

http://forums.pelicanparts.com/porsche- ... boxes.html

If you take note that a vw beetle has transmission frame horns and Porsche doesn't. So this 911 adjuster shown above won't work . Additionally these require shortened trailing arms.

I love when I'm told something can't be done..., so I closed my garage door and made a set of Inside Adjustable Pivots with a blind nut on the inside of the frame horn that use stock irs arms.

Difficulty level - challenging to say the least.

If you'd like, I'll see if I can find the drawing on this. In the mean time, heres a link to what the pieces look like before assembly.

Page down about halfway. Its about another topic, but it shows the pivot.
http://www.speedsterowners.com/topic/na ... iling-arms

David / dd-ardvark