Camber adjustment with IRS

[juse]

What options there are to make an IRS rear-axle fully camber adjustable?
I know that Porsche 944 trailing arms have an adjustment for toe and camber, but converting to Porsche bits is too $$$ for my budget.
Swapping trailing arms and rewelding shock mounts wont go with Finnish authorities.
Oliver; is there any high-tech "käfer-cup way" for this?

Justin

[Steve C]

Hi

You can just use the early 944 spring plates and then you would just need to drill 1 extra hole in your bug trailing arm to make it like a steel 944 arm.

Steve C

[juse]

I would go the porschepart-way if I had the money...I would like to do several other things if I had the money...but with a low budget I`ll have to make up something else.
Justin

[Wally]

Justin,
IMO there is no camber adjustment possible in the rear, not even with the porsche parts. The porsche parts only allow fine ride heigth adjustments (it has an extra excenter bolt for this) and toe adjustment. Toe adjustment is already possible with all IRS and swing-axle set-ups...
This question was also discussed in another GL forum, if I remember correct. It was suggested that camber was only to be altered, when you would reweld the pivot point of the arm (in the corner fork/torsion housing) at a higher level (if you want to reduce camber).
Walter

[ricola]

It is possible to adjust camber, I've done it!
Enlarge the holes in the spring plate and rotate the trailing arm in these holes.
For example, if you want more -ve camber on the rear right wheel, as you look at the hub from the side, rotate it anticlockwise, then tighten up again...

Hope this helps,
Rich

[Wally]

Rich,
I must have my suspension definitions mixed up, I guess, since I thought camber meant the 'vertical-ness' of the wheel. i.e. if the wheel stood 100 % straight or vertical, than camber was '0'. And if you have a swing axle with a lot of lowering, you got a lot of negative camber.
Also when you proceed as you describe, with elongated holes and the trailing arm goes down i.e. turns anti-clock wise, then you will also raise the cars suspension? When than as a side effect the camber also changes, than I really wouldn't describe it as a adjustable camber setting methode, but than again I'am really no suspension guru...
Or have I got it all mixed up???
Thanks in advance for any explanations.
Walter

[lightning bug]

Wally- You are correct.

Rich- You are speaking of caster, not camber.

Both get mixed up alot.

[ricola]

Sorry, I'm correct on this one as I have done it!
Wally: you are correct in what camber is...

If you think of the axis of the rear stub axle, it is not in line with the rotation axis if you rotate it in the way I described. The rotation axis being the inner trailing arm bush and a point in the middle of the 3 bolts on the spring plate. I agree that the caster of the assembly is changed but don't think it has any real affect on this suspension design.

Rich
PS when I said elongate the holes on the spring plate, do it in such a way that enables the movement that I described, not all parallel.

[Steve C]

hi

To get the most out of what you have as far + camber is concerned, jack up car, loosen the bolts & nuts on your spring plate, put a jack under the shock mount and raise it until all slack is taken up, tighten bolts, this will give you maximum + camber, your moving the arm anti clockwise like Rich said, if want a little more do what Rich said to do with bolt holes.

Steve C

[lightning bug]

I'm sorry. I thought you were speaking of something else. My apologies Rich.

[ricola]

Don't worry, I had to think about it for a while to convince myself it would actually work after a friend told me of this method...

Rich

[Chris Percival]

So basically you are lowering the car, without changing the splines on the torsion bar, to gain some camber?

[juse]

So I could weld an eccentric adjustable fixing onto the springplates connection holes (similar to the one on front controlarms inner mounting)?
I have understood that Porsche 944 uses something like this?
Justin

[ricola]

No, the ride height doesn't change noticably, you just change the angle of the hub in the spring plate. The 944 has an eccentric bolt for this...
Rich

[Chris Percival]

I still don't get it, maybe I am just being dense. Can someone draw me a picture?

[ricola]

Visualise a straight line, which goes through the inner mounting and the centre of the spring plate/trailing arm bolts. This is the axis that you are rotating the arm about... The hub axis goes from the end of this line out at an angle.
So, if you rotate the arm, as the hub axis is not on the same axis as the rotating axis, the end of it will go up or down, giving camber change.

Does that make sense?

[Chris Percival]

Sorry, I must be thick, I just can't see that. Surely the hub can only be at a position transcribed by the arc set by the forward mount of the trailing arm?

[juse]

When I said;

"So I could weld an eccentric adjustable fixing onto the springplates connection holes (similar to the one on front controlarms inner mounting)?
I have understood that Porsche 944 uses something like this?"

I meant that could this eccentric adjust camber/toe as it does on 944?
This wouldnt change the ride height, but the angle of the line that draws trough trailing arms connections compared to tire.
And for clearing the subject; I am talking about camber here, nothing else this time.

Justin

[ricola]

Chris
Grab me at the weekend at the Volksworld show and I'll explain. My car will be in the clubs area...

Rich

[Chris Percival]

:) Ok, will do (if I am going, I think I am)...

[juse]

What about these camber-boxes that are common on racing Porsches?
Has anyone installed one on a Beetle?
http://www.aerotechnik.com/dijitrace/itm00066.htm
http://www.autometricsmotorsports.com/images/Cars/Ron/ron_930_trailing_arm.jpg

Justin

[Richie]

Those camberboxes work wonders when installed in a Porsche. You can decrease camber after extensive lowering and it lessens diving under hard braking. Unfortunately there is not enough room in a bug unless you're handy with a large hammer :D
I haven't installed them in a bug, but I did on various track Porsches. I did however do a similar thing to a bug by elongating the holes, in which the M 14 bolthead fits, upwards and filling the bottom part with a crescent shaped piece of metal. This way I decreased the amount of camber. The reason for having too much camber was because the IRS-arm adaptors were welded in too low.
Keep us posted if you ever decide to fit camberboxes to your bug.

Cheers,

Richard

[juse]

After considering those boxes a bit more I figured out that they might not work with torsionbars. Any kind of camber adjustment from the inner connection of the trailingarm would put some axial bending stress on the bars. So this leaves only one choice for camber adjustment with an stock IRS: from the springplate fixing point.
Those camberboxes would make an ultimate set-up with coil-overs, after eliminating torsion bars by connecting the springplates to chassis with rod-ends (heim-ends,uniballs).
So any opinions of my idea to add an eccentric to the springplate as on 944?
Justin

[Wally]

Justin,
Wouldn't the spring plates absorb the axial bending stresses you mention ? The resulting axial stresses would then be minimal IMO. The springplate also absorbs the 'normal' camber changes when the wheel goes up and down, doesn't it?

Chris,
I still don't get it either how elongated holes or excenter bolts in spring plates would change camber instead of either changing ride heigth and thus changing caster (not a misspelling this time) imo or lengthening the spring plate and thus changing toe.
The working of the camber box I understand I think.
Anyway, sometime I may learn his also...
Walter

[juse]

I`m not sure of the springplates stress absorbing charasteristics, has anyone installed these in to a Beetle?
Richie; did those Porsches use torsionbar or coil-over with the camberbox?
And for the eccentric on springplate, I understand that on 944 it adjusts toe and camber simultaneously, and this only moderately. Any Porsche-owner comments on this?
Justin

[Richie]

Justin,

These cars had coil-overs, but IMO it doesn't matter if you use them with torsion bars or coil-overs. Just don't overdo it. Porsche moved the fulcrum (I think it's named that way?)-point 10 mm upwards in their 930 (old 911 Turbo) to reduce the rear squatting under acceleration. The 930 uses torsionbars so it seems it can be done.
Good luck,

Richard

[juse]

Ok, thanks Richie. I`ll see if I can make those boxes myself.
By the way; what does IMO mean?
Justin

[Richie]

Sorry Justin, IMO is something I picked up during forumsurfing.
I believe it means: "In My Opinion".
Good luck and keep us posted about the camberboxes!

Richard