Upper Control Arm Geometry Correction

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GTMaracucho

GTMaracucho

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Hi my friends, I planning built my own upper control arms, and i need infromation about the correction of geometry.
If you can recomended a good book to read, will be apreciated.

Regards ... Jose
 
Correction "from what"?
 
If you raise the caster then you will have a bump steer problem that you will have to fix.
 
GTMaracucho said:
About the Caster problem of stock arms
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Ok. I thought maybe that's where you were going. Wasn't sure. I had a friend years ago who relocated the upper control arm brackets at the top of the frame rail like 1/2" toward the rear of the car and he ended up with like 6* caster using the stock arms. It was different, but it worked.
 
brian6pac said:
If you raise the caster then you will have a bump steer problem that you will have to fix.
Click to expand...

I've never seen anyone get bump steer from increasing caster using offset bushings. So how does increasing caster create bump steer? Bump steer has to do more with the travel of the tie rod. Read here:

Technical Articles
 
By raising caster you move the upper control arm back, this moves the steering arm down. Now you have to lower the car or raise the steering arm. Or you could move the idler arm and pitman arm down, that would be difficult.
 
RustyRatRod said:
I've never seen anyone get bump steer from increasing caster using offset bushings. So how does increasing caster create bump steer? Bump steer has to do more with the travel of the tie rod. Read here:

Technical Articles
Click to expand...
I used to set up bump steer on race cars so I understand all of it, did my first one in 1979.
 
RustyRatRod said:
Ok. I thought maybe that's where you were going. Wasn't sure. I had a friend years ago who relocated the upper control arm brackets at the top of the frame rail like 1/2" toward the rear of the car and he ended up with like 6* caster using the stock arms. It was different, but it worked.
Click to expand...
Do you
brian6pac said:
By raising caster you move the upper control arm back, this moves the steering arm down. Now you have to lower the car or raise the steering arm. Or you could move the idler arm and pitman arm down, that would be difficult.
Click to expand...
I'm talking about this !!!!

Screenshot_2018-01-01-19-40-38.png
 
What are you using for pivots, IE tubing with factory Mopar style or poly bushings, or heim ends? What I would do is take careful measurements of a stock "known good" arm and lay that out. Then obtain (buy) a set of the Moog offset bushings. Measure them to see how much offset they provide. Then "tack up" a prototype with enough strength to hold it together, and short enough beads you can knock it apart. Assemble and attempt to align the front end. You will easily see if you are running out of adjustment room. If you are using heim ends this should be easier as they have more range.
 
GTMaracucho said:
Do you

I'm talking about this !!!!

View attachment 1715414793
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O.k so before you get carried away with reinforcing it put it together and set your toe just use a tape measure it's easy. Now jack up the front 2" and measure the toe again or better yet don't adjust the torsion bars so you can let it all the way down and check the toe.
 
RustyRatRod said:
I've never seen anyone get bump steer from increasing caster using offset bushings. So how does increasing caster create bump steer? Bump steer has to do more with the travel of the tie rod. Read here:

Technical Articles
Click to expand...

By putting in offset bushings you just putting a band-aid on a sagged frame. Putting it back were it was in the beginning.
 
GTMaracucho said:
I'm planning built a tubular ones
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I understand. Your picture is pretty self explanatory of what you're wanting to do. Good luck with it and keep us posted. How much caster are you aiming for?
 
RustyRatRod said:
I understand. Your picture is pretty self explanatory of what you're wanting to do. Good luck with it and keep us posted. How much caster are you aiming for?
Click to expand...
This is the cuestion. This is the reason that I need a good book in order to know what I doing
 
GTMaracucho said:
This is the cuestion. This is the reason that I need a good book in order to know what I doing
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I'm not sure there's a better book than the Mopar Performance Suspension book, ninth edition. I don't think it touches on control arm mods, but it has tons of information that I have no doubt will help. Mancini has them pretty cheap I think. That's where I would START.
 
RustyRatRod said:
I'm not sure there's a better book than the Mopar Performance Suspension book, ninth edition. I don't think it touches on control arm mods, but it has tons of information that I have no doubt will help. Mancini has them pretty cheap I think. That's where I would START.
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Thanks a lot
 
Yes the mopar books are great the front suspension racing manual has all the info you need to understand front end geometry.
Here is a page from it of what happens to bump steer when you lower the outer steering arm, and that will happen if you raise caster a lot.

img500.jpg
 
GTMaracucho said:
Hi my friends, I planning built my own upper control arms, and i need infromation about the correction of geometry.
If you can recomended a good book to read, will be apreciated.

Regards ... Jose
Click to expand...

The Control Arm itself doesn't really change the geometry. I think you're thinking of the Hotchkis E-body upper control arms kit. The Hotchkis "Kit" is one upper control arm assy and one bracket to relocate the rear chassis pick up point.

When Hotchkis computer plotted the E/B-body front geometry, they found an improvement relocating that rear chassis pick up point.

When Hotchkis computer plotted the Abody front geometry, they found no improvement relocating anything.

You can move the upper ball joint rearward to get positive caster. Firm Feel & Hotchkis, tubular upper arm do this.

If you don't know how to much to move the ball joint back, you should just buy some arms.
 
Kern Dog said:
No.
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Well it might not be a problem for you guys out on the west coast but for the east coast chuck holes, cars here back in the 70's need alignments every 6 months or so, and after a while you can't get 0 camber any more, so moog came up with the offset upper control arm bushing.
 
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