Custom bracket to raise the rear upper control arm

[99gst_racer]

I'm working on fabbing a set of these to raise the inboad pick-up by 1". I spent some time measuring and drawing last night. It seems that for the arm to clear while being raised 1", it would also need to be kicked outward about 1".

That's where I get concerned. 1" seems like too much positive camber gain but maybe I'm wrong. And I don't think it can be compensated for unless you can shorten the upper arm or lengthen the lower arm, which would require an an adjustable arm for either.

Thoughts on this?

This basically shows where the new hole would have to be:

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[crash89]

What is the reason for this? Just a different solution for front camber or..??? Im pretty interested in seeing how much this changes things, for sure. Seems like a cool idea.

 

[99gst_racer]

The purpose of raising the pivot point is to raise the rear roll center. It would perfectly compliment the subframe I just finished.

 

[greengoblin]

If it has to be moved out that far to clear the bolt head fort the bracket perhaps you could use a lower profile and bring the arm in more.?

 

[99gst_racer]

How far could the pivot point be moved outward comfortably? How much do most poeple shim the the mount out to gain camber after lowering?

I just remeasured and I do have more room that I thought. I mght be able to pull it in about .400". So, it would be outward about .600" from the original hole. That shoudln't be a problem, right?

 

[4g63tc]

why not just Modify the 3g tubular arms to accept Heim joints, kicked out at a 45 degree downward angle? that way the camber, and pivot point, can be adjusted, wile leaving the stock brackets untouched.

I've been kicking around this idea in a search for adjustable uppers in the rear.

 

[99gst_racer]

why not just Modify the 3g tubular arms to accept Heim joints, kicked out at a 45 degree downward angle? that way the camber, and pivot point, can be adjusted, wile leaving the stock brackets untouched.

I've been kicking around this idea in a search for adjustable uppers in the rear.

I'm all about some aftermarket arms, but to raise the roll center, the pivot point needs to be raised. And that can only be done at the mounting bracket.


I think I can make it fit with it kicked out .600". This is about where it would be. If I can find some 3/16" plate tomorrow, I'll cut and weld up a prototype bracket this weekend and and see how it fits.

 

[greengoblin]

Paul you should talk to Brain and Eric. They just did all the alignment stuff to there cars recently. I'm sorry I can't be more help. My advice is keep is as close in as possible. Not every ones cars is going to be the same and some may even require more shiming from one side to the other. Also still think changing the bolt out to a high grade low profile unit would be a good idea.

Also remember if you shorten the arm you are goign to affect other things like the camber curve.

Kevin

 

[jdsoza]

I love the bracket idea! Having to move it out just over one-half inch will definitely cause some positive camber. Adjustable arms will be needed. My thought which might be dumb is this, If you are moving the arm up one inch, wouldn't it technically pull the knuckle in giving more negative camber? since the distance at say factory angle is ""y" point (control arm) to the knuckle "z" point is a set distance. wouldn't changing to the new angle "x" (raised pickup) need a technically longer arm since its higher to retain stock camber, but if you used the short arm it would pull the knuckle in giving negative camber?

 

[fjm9898]

jdsoza i see where your getting at but i think it works in a opposite way after the car is lowered. when you lower the car the knuckle is being raised which in turn deflects the upper arm up, making it shorter. this is also why the camber change happens as well as the roll center change when you lower the car. when this bracket raises the arm back up with will become longer again. this would also probably correct the arm deflection and fix a slight camber change but then pushing out making the camber change even higher back to positive.

i think making a custom tubular arm would be bad ass (like the 3g) with camber adjustment at the ball joint to the knuckle, kinda like the SPC front arm.

 

[greengoblin]

I love the bracket idea! Having to move it out just over one-half inch will definitely cause some positive camber. Adjustable arms will be needed. My thought which might be dumb is this, If you are moving the arm up one inch, wouldn't it technically pull the knuckle in giving more negative camber? since the distance at say factory angle is ""y" point (control arm) to the knuckle "z" point is a set distance. wouldn't changing to the new angle "x" (raised pickup) need a technically longer arm since its higher to retain stock camber, but if you used the short arm it would pull the knuckle in giving negative camber?

Remeber the cars on lowered cars the arms are angled up. If you move the inboard pickup point up you bring the arm angle back down and that adds positve camber back. Remeber the arm swings in an arch. As the car goes into bump camber negative camber is added. As it goes in to droop negativecamber is reduced. If Paul moves the pickup point up and out it will add more positive camber than just shiming a lowered car.

If the arm is shortend or lengthed it will also effect the camber curve.

I hope that makes sense.

Kevin

 

[turbosax2]

Paul you should talk to Brain and Eric. They just did all the alignment stuff to there cars recently.

We used the SPC camber kit on Brian's car, so I can't say how much affect 0.5" of spacing would have on camber.

But...if you wait until next weekend, hopefully my car will be getting the new suspension, corner balancing, and alignment. I wasn't completely satisfied with the SPC kit, so I'm going to try using spacers instead. I plan on measuring camber with no spacers, then slowly increasing to get a nice plot of how camber changes. Of course, no guarantees this translates directly once the arm has been raised.

 

[jdsoza]

i guess i should've been more clear, i was going from stock height perspective. I definitely agree with what you guys are saying about a lowered vehicle. anybody seen the Nagisa arms for an RX7 FD3S? They don't adjust at the ball joint, but at the mounting on the body. They can go like +-10 degrees, this should compensate for enough camber.

 

[99gst_racer]

Worst case senerio, I could also whip up an adjustable chromoly upper arm to compensate for the kicked-out pivot point. I was really trying to keep costs down on this venture though.

 

[greengoblin]

Why is keeping cost down so damn hard? Oh yeah its because we want it all.


With your lower arms you have already built you may have enough camber adjust in the lower arms to compensate. You would even gains some track width. The real question is can the axle move as much as needed.


Kevin

 

[99gst_racer]

With the adjustable lower arm, you could definitely compenste and keep a stock upper arm. I'd be willing to bet the axle would handle the extra bit of width. I'd bet you wouldn't have to extend the lower all that much.

Though, the adjustable upper arm woud be great for anyone that doesn't have an adjustable lower.

 

[fjm9898]

well if you going through the trouble of making an adjustable rear might as well make an adjustable front

 

[jdsoza]

@ Paul, can you pm with some of the materials you would need to build an upper arm? I got a friend who's a fabricator and might be able to help out with some materials. for how much you're doing for all of us dsm guys, id be willing to chip in for r&d.

 

[99gst_racer]

@ Paul, can you pm with some of the materials you would need to build an upper arm? I got a friend who's a fabricator and might be able to help out with some materials. for how much you're doing for all of us dsm guys, id be willing to chip in for r&d.

I already have all of the materials. I'd just need to jig it up and buy a bender. But I'd like to try to achieve raising the inboard pivot point successfully without using an aftermarket arm (if possible).

 

[99gst_racer]

I welded up a bracket tonight just to see how it fit. This is raised 1.00" and moved outward about .475". It only clears the backside of the mount by about .100" and it's right up against the mounting bolt head. I'd like to get the rear clearance to at least .250", so it seems the best I could do it have it pushed outward about .600". And that should be OK if used with either and adjustable upper or lower arm. Although, I would be curious to see how much camber it gains with stock arms on a car lowered at least 1.5".

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[psycho]

I remember using 10 washers on my car. And I still have 1 degree of negative camber. How's that for "every car is different". Haha

 

[fjm9898]

well could you make aftermarket arms like i explained for those who want them

 

[lowell]

How about a thicker mounting plate with a countersunk bolt?

 

[snowborder714]

That will move the arms out, which we don't want.

 

[turbosax2]

I forgot to get a baseline height before lowering my car so I'm not sure how far from factory it is lowered. I have about 14.5 inches from the center of the wheel to the fender.

No spacers on the rear control arm: -1.5* camber
0.60" of spacer on the rear control arm: -0.2* camber