Lower control arms

[Nick9one1]

I have a sandrail built on a 1303 Beetle chassis (the one with McPherson struts).
I'd like to build new arms so they have more camber adjustment.

Below are some images of a standard lower arm/ARB. And an arm someone else has made.



Rose joints are overkill. So I'd like to build something similar that can house the original bushes and balljoint- which is press in.

I came across this design..

I would just need to find a tube with an ID the same as the poly bushes/balljoint and weld some M18 threaded rod to it.
But basic rod is 4.8, which I don't think is weldable?

Any thoughts?

 

[Brad93]

Highly stressed component, originally pressed or cold forged, replaced with a piece of tube that has had some random all thread welded into it. Good luck with that one in court.

 

[PhillipM]

Just use an offset polybush in the original arms?
Although I can't say I'm a big fan of polybushes especially on something light like a sandrail, too much friction, I tend to avoid them wherever possible.

 

[minimutly]

Be careful. The threaded end that attaches to the bush in the pic looks like it's welded around the end only. If the weld fails then it's curtains. Properly made ones will be tig welded with a wrap around second piece tig welded to both pieces. Personally I wouldn't use an adjustable lower arm, I would make it fixed length and do away with the threaded bit.

 

[Moose McAlpine]

Highly stressed component, originally pressed or cold forged, replaced with a piece of tube that has had some random all thread welded into it. Good luck with that one in court.

Don't have to appear in court if you also don't survive the inevitable crash!

Follow me for more legal loopholes.

 

[Nick9one1]

Thanks. As I suspected.
Looks like rose joints are the only suitable solution (like this).
Although there isn't really much pointing making the inner side adjustable, as it would change the location the ARB joins the arm. Would make sense to leave that as a bush.

 

[frank horton]

there will a pre manufactured susp arm made already.....dread to think of the cost tho....
look in the US for "better" idea's...
Home made things for that use need to double the thickness of the orig to keep some of the strength but then often somewhere they r just to fat to fit prop...
then of course it all starts to get out of hand making everthing fit...
This is why there are companies making KIT's...loads'a money.....

 

[piman]

Nick,

a common modification for adjusting camber is to vary the location of the upper mount, i.e. locate it further inboard. That may be an easier and safer modification.

Alec

 

[tigdlo]

This forum is wierd somethimes, someone buys some cheap far east aftermarket suspension components and bolts them to their car - 17 likes. Someone wants to design and make something, tumbleweeds or you are going to kill every other road user within a 2 mile radius in a nuclear style explosion as soon as you get to 13 miles an hour and go to court and we should bring back public hangings for people like you.......

Camber adjustment may be better taken car of at the hub to strut joint, the bottom bolt would be the pivot and the top bolt adjusted in a slotted hole, standard on many VAG cars around the 90s. To get an appreciable camber change altering the length of the track control arm you will also be changing the track by a considerable amount too.

Are you needing more camber adjustment because the car is lifted compared to the original beetle? If so, how has that been acheived? If the suspension has more travel in rebound than the standard car then ball joint alignment would need to be a greater consideration, although should always be considered and checked when making any suspension modifications.

That red arm isn't well designed in my amateur opinion and should not be copied. Look up shear and moment/bending loads of beams and you should be able to understand why as there appears to be no reinforcement where the ARB/tie bar is attached, see the first 10 seconds of this rant, https://www.youtube.com/watch?v=5kp3oVMgYVw&t=554s If used for a lifted car, to give the ball joint the travel required, I wouldn't expect the thread of the rod end to be aligned with the axis of the tube

Probably best not use welded M18, or any size threaded bar of any grade for suspension components, too many unknown variables.

Depending on the use of the car I would probably keep it sinple, make the arm the correct length to get the camber I want within the original adjustment with the standard ball joint in a housing that gives it the correct angular alignment for the ride height/suspension travel and make it thicker/heavier than the standard arm.

 

[JohnH]

Cant you just modify the standard adjustable inner bush shown in the diagram.
Modify the mount to take larger round bits and make new offset round bits to fit on a new bolt.

These are off an old BMW. Standard on the right and modified on the left.

Below is the modified mount;

 

[pedrobedro]

You'll need a left hand and a right hand thread at the ends of the tie bar to get fine adjustment.

 

[tigdlo]

You'll need a left hand and a right hand thread at the ends of the tie bar to get fine adjustment.

Changing the length of the lower control arm 1mm with give an approximate 0.1 degree camber change so an M18x1.5mm thread would give 0.075 degree for half a turn, plenty fine enough but a bit of a faff having to unbolt it to make an adjustment though, not likely much of an issue unless it's a race car.

The left and right threads would have to be on the same end of the control arm because the tie bar/ARB would prevent it from being rotated.

 

[Nick9one1]

Nick,

a common modification for adjusting camber is to vary the location of the upper mount, i.e. locate it further inboard. That may be an easier and safer modification.

Alec

Hi, thanks. That was my other thought. The top mounts already have camber adjustment, but may be able to get a small amount of castor too.
Because the car is running 944 hubs, it needs more adjustment than expected.


These are usually sold as castor plates but could mount at 90 degrees.

like this




But I dont think there will be enough adjustment

 

[Nick9one1]

This forum is wierd somethimes, someone buys some cheap far east aftermarket suspension components and bolts them to their car - 17 likes. Someone wants to design and make something, tumbleweeds or you are going to kill every other road user within a 2 mile radius in a nuclear style explosion as soon as you get to 13 miles an hour and go to court and we should bring back public hangings for people like you.......

Camber adjustment may be better taken car of at the hub to strut joint, the bottom bolt would be the pivot and the top bolt adjusted in a slotted hole, standard on many VAG cars around the 90s. To get an appreciable camber change altering the length of the track control arm you will also be changing the track by a considerable amount too.

Are you needing more camber adjustment because the car is lifted compared to the original beetle? If so, how has that been acheived? If the suspension has more travel in rebound than the standard car then ball joint alignment would need to be a greater consideration, although should always be considered and checked when making any suspension modifications.

That red arm isn't well designed in my amateur opinion and should not be copied. Look up shear and moment/bending loads of beams and you should be able to understand why as there appears to be no reinforcement where the ARB/tie bar is attached, see the first 10 seconds of this rant, https://www.youtube.com/watch?v=5kp3oVMgYVw&t=554s If used for a lifted car, to give the ball joint the travel required, I wouldn't expect the thread of the rod end to be aligned with the axis of the tube

Probably best not use welded M18, or any size threaded bar of any grade for suspension components, too many unknown variables.

Depending on the use of the car I would probably keep it sinple, make the arm the correct length to get the camber I want within the original adjustment with the standard ball joint in a housing that gives it the correct angular alignment for the ride height/suspension travel and make it thicker/heavier than the standard arm.

Thanks, Some very interesting points.

the original knuckles/hubs/wheels/brakes have been swapped for Porsche 944 (direct fit but geometry is slightly altered). As a result there is a fair amount of positive camber.



After taking in your comments I wonder if it would be best to 'simply' extend the existing control arm to bring the camber to 0 degrees, then as you suggested, use a top mount adjustment plate

 

[PhillipM]

It's a pity the frame is already painted the best solution would probably have been to just bring the top mounts with a cut and weld, like you're saying with the top mount plates.
Although given the lack of reinforcement up there I'd be inclined to keep the OEM rubber top mounts anyway just to keep shock loads down on the 'wings' there

I would be taking a look to see if you can use offset mounting bolts in the uprights to damper joint though, as Tigdlo mentions - that could be a very cheap and easy way to do things if there's something suitable around.

 

[tigdlo]

I take back my previous comment on making the arm longer and the correct length being the simple solution, I assumed it was lifted and a longer arm would put the lower balljoint back in it's original position.

Altering the length of the control arm and moving the top mounts will adjust the camber but will also change the KPI altering the scrub radius, i doubt it will move it out of an acceptable range but I would personally want to know where it was to be sure.

If you are more inclined to the longer control arm solution because you want to replace as it's ugly and doesn't really fit with the whole aesthetics of the car you can still do that, they don't have to be longer. Also they would have to be longer outboard of the tie bar/ARB mount increasing the load on the arm.

If you do decide to adjust the knuckle to strut joint you can to it very simply by sloting the hole in the direction you want it to go, add a couple of thick, large washers, set your camber and tack them in place, I think given the changes that have been made I would do this, it's practically free and easier than anything else to get the car usable.

 

[hotponyshoes]

If you thread one end of the tube, put an insert in that with a locknut, then the rose joint threaded into that with another locknut you'll have infinite adjustment without needing a thread in each end or needing to rotate the tube.

 

[Nick9one1]

for completeness, here is the original thread for the adjustable arms https://germanlook.net/forums/showthread.php?t=11598
and another discussing the geometry changes between the 944/beetle stub axle https://www.thesamba.com/vw/forum/viewtopic.php?t=665668

I think the first thing I need to do is get a baseline of exactly where the geometry is now.
I found really interesting project for home camber, castor and toe measurement https://www.diyfabshop.com/alignmentkit. It's a shame it doesn't also do kingpin inclination.

 

[bricol]

Hi, thanks. That was my other thought. The top mounts already have camber adjustment, but may be able to get a small amount of castor too.
Because the car is running 944 hubs, it needs more adjustment than expected.
View attachment 511599

These are usually sold as castor plates but could mount at 90 degrees.

like this




But I dont think there will be enough adjustment

You are confusing castor and camber - you've already got more castor adjustment than I've ever seen on a car! Looks like you could go negative on the castor, which would make it a very tense, hard working drive!

 

[Nick9one1]

sorry - Wrong way around in post #13. Otherwise correct.