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front suspension height and torsion bar adjustments

Started by preid, March 15, 2013, 11:23:44 PM

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preid

I want to first measure my front suspension height and compare to factory setting before determining how much I may need to adjust torsion bars, so, I have 2 questions:

1)  The service manual says to determine the front suspension height as follows:  "measure distance from lowest point of one adjusting blade to floor (meas. A) and from lowest point of steering knuckle arm to floor (meas B), The difference should be 1 7/8" +/-1/8".  Question is, can anyone explain or have a pic that shows where the adjusting blade is?  There is a pic in the manual but it isn't much help.

2)  Assuming I need to adjust the torsion bars, I plan on:
a.  raise front end only, setting the frame on jack stands
b.  rotate adjusting bolt as needed (thats all the manual says to do), however, I've seen mention in posting here where you should also loosen LCA pivot nut before adjusting bolt.  See link below.

http://www.dodgecharger.com/forum/index.php/topic,84884.0.html

Does anyone know for sure if I need to loosen the pivot nut? 

3)  Once torsion bars are adjusted, check/correct wheel alignment.

Really appreciate any help on this!

thanks.

green69rt

I don't have my manual in front of me now but....   set your car on a level surface(????)  now measure from the lowest part of the adjusting arm to the floor ( whats this mean???, the arm that is pushed by the screw that you use to turn to adjust the height.) Really this does mean the lowest part of the arm.  Not the pin, not the round part that supports the pin but the lowest part of the arm.  The screw pushes the arm and raises the car??  This is the arm that is inside the lower control arm.  Then you need to find the stearing knuckle and measure that distance.  The dif is the 1 and 7/8. So find the lowest point on the blade to start.  I know it's really hard to get the info from the manual but keep working. Hope this helps. To do this adjustment do NOT take weight off the front end!!! leave it as is and take the measurements.  No jacks, supports or anything else.  The front end height and allignment is made using the cars normal resting weight.

preid

Quote from: green69rt on March 16, 2013, 12:22:23 AM
I don't have my manual in front of me now but....   set your car on a level surface(????)  now measure from the lowest part of the adjusting arm to the floor ( whats this mean???, the arm that is pushed by the screw that you use to turn to adjust the height.) Really this does mean the lowest part of the arm.  Not the pin, not the round part that supports the pin but the lowest part of the arm.  The screw pushes the arm and raises the car??  This is the arm that is inside the lower control arm.  Then you need to find the stearing knuckle and measure that distance.  The dif is the 1 and 7/8. So find the lowest point on the blade to start.  I know it's really hard to get the info from the manual but keep working. Hope this helps. To do this adjustment do NOT take weight off the front end!!! leave it as is and take the measurements.  No jacks, supports or anything else.  The front end height and allignment is made using the cars normal resting weight.

Thanks for the feedback!  See pic attached, is the red arrow pointing to the lowest part of the adjusting arm that you described?
Yes, I do realize I need to take these measurements w/ the car resting on its wheels.  I have a 2nd question in my orig. posting that asks about the adjustment procedure where I know you will need to take the weight off the wheels, can you take a look and provide any insight?

thanks,
Paul

HPP

Lift the car so the front tires are off the ground, crank in/out one complete turn of the adjusting nut, drop, bounce, roll back and forth at least 5' in one direction, recheck height, repeat as necessary.

Picture of height check below;


preid

Quote from: HPP on March 16, 2013, 10:11:21 PM
Lift the car so the front tires are off the ground, crank in/out one complete turn of the adjusting nut, drop, bounce, roll back and forth at least 5' in one direction, recheck height, repeat as necessary.

Picture of height check below;



Perfect, HPP
That picture helps a lot.  Thats a lot clearer of a picture than whats in my manual.

thanks again!  :cheers:

XH29N0G

I know this is an old topic, but I want to make sure I understand correctly.

The X carline (charger) The measurement of "A" would be from the adjusting blade, which is the black arrow in the first attached image rather than the yellow arrow or the green arrow.

The measurement of "B" would be to the housing (double yellow arrow) in second attached image.

Right?
Who in their right mind would say

"The science should not stand in the way of this."? 

Science is just observation and hypothesis.  Policy stands in the way.........

Or maybe it protects us. 

I suppose it depends on the specific case.....

green69rt

I think you have it right.   Hard to see if the point on the steering knuckle is correct, but it looks right.  Figure 2 in the previous post looks correct. My recollection is for a 69 Charger.   I think other models or years may be different.

ws23rt

Quote from: preid on March 15, 2013, 11:23:44 PM
I want to first measure my front suspension height and compare to factory setting before determining how much I may need to adjust torsion bars, so, I have 2 questions:

1)  The service manual says to determine the front suspension height as follows:  "measure distance from lowest point of one adjusting blade to floor (meas. A) and from lowest point of steering knuckle arm to floor (meas B), The difference should be 1 7/8" +/-1/8".  Question is, can anyone explain or have a pic that shows where the adjusting blade is?  There is a pic in the manual but it isn't much help.

2)  Assuming I need to adjust the torsion bars, I plan on:
a.  raise front end only, setting the frame on jack stands
b.  rotate adjusting bolt as needed (thats all the manual says to do), however, I've seen mention in posting here where you should also loosen LCA pivot nut before adjusting bolt.  See link below.

http://www.dodgecharger.com/forum/index.php/topic,84884.0.html

Does anyone know for sure if I need to loosen the pivot nut?  

3)  Once torsion bars are adjusted, check/correct wheel alignment.

Really appreciate any help on this!

thanks.

I would like to answer the question about loosening the lower control arm pivot mount nut.
Since I have not seen it said in print it is only from my experience that it can make a difference.
First the lower control arm shaft has a snug rubber bushing that is pressed into the adjuster arm/hex mount for the t bar.
It is intended to flex the small amount that the t bar will twist in operation.

If the LCA nut is torqued when all load is off the t bar than as the bar is loaded the bushing has to flex much more than intended.

When the nut is left loose and the car is lowered and adjusted for height the shaft of the LCA can turn in the K member without twisting the bushing as the LCA and the t bar find their position.

At that point torquing the nut will hold the shaft fixed in the K member and the t bar will twist on the rubber bushing the amount intended.

I admit that with a new bushing it may slip on the shaft but the fit is tight and it just may tear the rubber. An old one is less likely to slip.

Lets say the car is on the ground way low and the LCA shaft is torqued in the K frame. The t bar is now one with the K frame but for the bushing.

Now adjusting the height (lowering the LCA) will twist the bushing and the t bar together. So now the height is good but much of the twist load is in the bushing.

After driving some the LCA shaft in the K frame may slip giving up some load from the bushing and now more is on the t bar. This will show up as the LCA is lower. (car higher).

I believe this is why it is best to leave the LCA connection at the K frame loose till the height is right. Now the Bushing can flex both ways as the t bar flexes both ways.

So torque the LCA nut last with the car on the ground.


HPP

The factory manual instructions are for making slight variations to a car that has already been assembled in the factory and has a certain "set" already  in the assembly.

If you are rebuilding a suspension from new, you are correct that you would want to wait to torque everything to spec until there is weight on the car and you are close to desired ride height as tightening everything down while it is hanging will introduce errors and open you up to potential issues later.

In my experience, an alteration of less than two inches of height change at the fender, not control arm bumper change, does not require a resetting of the pivot nut. If you wanted to move things around more than that, it might be worthwhile to loosen the thing up and reset them.