Modifying Trailing Arms For More Camber Options

[yeahmag]

I'm considering building a jig for my trailing arms and then sectioning them and clocking them for more negative static camber and toe. I simply can't get more than just shy of 2 degrees and I need more. No shims are in and the tub is fairly straight. She's already lowered to the point that I've had custom length and valved Penske double adjustable shocks made and run ridiculously high spring rates.

Has anybody done something like this of found another way to pick up more rear camber?

[JamesM]

https://tangerineracing.com/shop/ols/produc...ng-arm-brackets

I think these are going the opposite direction of what you are looking for, (decreasing camber to eliminate the shim stack) but im wondering if you couldn't work something out with a similar concept of modifying the removable mounting bracket.

[ChrisFoley]

Hey Aaron, was that you I heard being interviewed on air about the flooding last week?

[ChrisFoley]

I usually have no trouble getting close to 2.5 degrees on a lowered car with stock trailing arms.
My solid brackets are for lowered street cars to eliminate use of too many shims.

I have tooling to do the trailing arm cut and reweld procedure (and add a bulkhead to increase stiffness - still the best/lightest/stiffest way to improve stock trailing arms) but I've never used that procedure to increase negative camber.





1/27/2023: edited for clarity

[slivel]

We couldn't get the camber that we needed on my car and solved the problem by welding up the hole on the inner suspension mounting ear and redrilling for more camber. I think my tub was slightly tweaked.

[yeahmag]

Hey Aaron, was that you I heard being interviewed on air about the flooding last week?

Not me, but man did we have a lot of rain. Pasadena and SoCal in general is just not prepared for that.

[yeahmag]

We couldn't get the camber that we needed on my car and solved the problem by welding up the hole on the inner suspension mounting ear and redrilling for more camber. I think my tub was slightly tweaked.

I've considered that, but was scared of putting the stress further out "on the lever" of an already stressed part. Seems to me like taking the same approach Chris has with a bulkhead and rotating the section to increase the static camber is pretty safe...

[slivel]

We couldn't get the camber that we needed on my car and solved the problem by welding up the hole on the inner suspension mounting ear and redrilling for more camber. I think my tub was slightly tweaked.

I've considered that, but was scared of putting the stress further out "on the lever" of an already stressed part. Seems to me like taking the same approach Chris has with a bulkhead and rotating the section to increase the static camber is pretty safe...

When you change the shim stack, you are departing from the plane of the surface of the inner mounting ear are you not? In my case the tub was tweaked enough that the toe was also difficult to get set so when we welded up the hole we applied some extra metal on the one side to compensate for that as well. In a perfect world, the horizonal and vertical component of the face of the inner mounting ear would describe the factory toe and camber of the rear wheel as the pivot shaft runs perpendicular to it. Any change to the angle will necessarily put some stress on the movement. With rubber bushings it is well within the ability to handle it but when you go to something less compliant there will be stress.

[dr914@autoatlanta.com]

usually by now the swing arms have twisted into the neg camber position and without shims and with shorter springs three degrees is par for the course. If your swing arms are that straight, just buy a used set and get all of the neg camber you need and sell your nice straight ones to someone who needs them !!!

I'm considering building a jig for my trailing arms and then sectioning them and clocking them for more negative static camber and toe. I simply can't get more than just shy of 2 degrees and I need more. No shims are in and the tub is fairly straight. She's already lowered to the point that I've had custom length and valved Penske double adjustable shocks made and run ridiculously high spring rates.

Has anybody done something like this of found another way to pick up more rear camber?

[yeahmag]

We couldn't get the camber that we needed on my car and solved the problem by welding up the hole on the inner suspension mounting ear and redrilling for more camber. I think my tub was slightly tweaked.

I've considered that, but was scared of putting the stress further out "on the lever" of an already stressed part. Seems to me like taking the same approach Chris has with a bulkhead and rotating the section to increase the static camber is pretty safe...

When you change the shim stack, you are departing from the plane of the surface of the inner mounting ear are you not? In my case the tub was tweaked enough that the toe was also difficult to get set so when we welded up the hole we applied some extra metal on the one side to compensate for that as well. In a perfect world, the horizonal and vertical component of the face of the inner mounting ear would describe the factory toe and camber of the rear wheel as the pivot shaft runs perpendicular to it. Any change to the angle will necessarily put some stress on the movement. With rubber bushings it is well within the ability to handle it but when you go to something less compliant there will be stress.

While I'm not sure I completely follow all of this, I do have the inner ear scabbed and I run the Rebel Racing Teflon rear bushing kit. One option I can do without much negative consequence is to relocate the hole on the outer adjuster up and forward. It wouldn't be much of a gain, but it would be some. I'm guessing I can use the shims as a mm-to-degree reference for the estimated gains.

[SirAndy]

I just bought a set of slicks that don't like any negative camber.
Specs call for 0 camber with -1 max.

Not sure if that route is cheaper, but certainly less work.
(IMG:style_emoticons/default/biggrin.gif)

[bkrantz]

Back in the day for my IT race 914, I raised the outer hole for the trailing arm pivot. Just weld and re-drill.

[slivel]

We couldn't get the camber that we needed on my car and solved the problem by welding up the hole on the inner suspension mounting ear and redrilling for more camber. I think my tub was slightly tweaked.

I've considered that, but was scared of putting the stress further out "on the lever" of an already stressed part. Seems to me like taking the same approach Chris has with a bulkhead and rotating the section to increase the static camber is pretty safe...

When you change the shim stack, you are departing from the plane of the surface of the inner mounting ear are you not? In my case the tub was tweaked enough that the toe was also difficult to get set so when we welded up the hole we applied some extra metal on the one side to compensate for that as well. In a perfect world, the horizonal and vertical component of the face of the inner mounting ear would describe the factory toe and camber of the rear wheel as the pivot shaft runs perpendicular to it. Any change to the angle will necessarily put some stress on the movement. With rubber bushings it is well within the ability to handle it but when you go to something less compliant there will be stress.

While I'm not sure I completely follow all of this, I do have the inner ear scabbed and I run the Rebel Racing Teflon rear bushing kit. One option I can do without much negative consequence is to relocate the hole on the outer adjuster up and forward. It wouldn't be much of a gain, but it would be some. I'm guessing I can use the shims as a mm-to-degree reference for the estimated gains.

If you are setting this up for track work, I recommend removing the rear spring and letting the trailing arm run through the normal travel. While doing this look at the outer camber /toe adjuster which should not be tightened down. Also look at the inner ear and see where the neutral position is for least tension. Then try to set the alignment settings that you want to end up with and it will become obvious where you need adjustment. You may be able to get everything you need on the outside, but I was not able to on my car necessitating some modification of the inner point. The precision of 70's vintage car building in the 914 left a lot to be desired. Tubs were not built to today's standards, and they do flex and rust /corrosion plays a factor.
I use and am a big fan of Tangerine Racing reinforced trailing arms. With my full cage , my car is very torsionally strong. This needs to be done on a track car running 2 to 3 times the stock hp, big brakes and wide sticky tires put huge stress an everything. Good luck with your project.

[brant]

I also wonder if you might have bent swing arms or a tweeked chassis.
I've never had a 914 that couldn't get to -2 degree's
and I currently have my race car at -2.5 with stock arms/pick up points, and chassis

[ChrisFoley]

With the trailing arms out of the car its not hard to check if they are tweaked.
Set the pivot shaft horizontal and the axle center at the same elevation. The wheel flange should have 1.5 deg negative camber.

[campbellcj]

Interesting thread - I'd have to dig up my alignment sheet to confirm but pretty darn sure mine is at around -2.5 rear as well with no mods. Height is set pretty low but not crazy.

[r_towle]

Adjustable inner ear mount…..hmmm

[eeyore]

Is it possible the arms are flipped side to side?