ride height question

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my68barracuda

my68barracuda

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per the FSM the ride height for my 68 Barracuda should be 1 3/8 +/- 1/8

I have read that the ride height needs to be set prior to an alignment as later changes to the ride height can affect the alignment.
I have also found the Skosh Chart with recommendations for caster and camber.

so my questions are
1) is the OE ride height specification still a valid requirement and that is what folks run?
Or with changes to tire diameter, stiffer rear springs and stiffer front torsion bars do folks tend to set the 'stance' they are after, lock down the ride height, then move forward with the alignment process.

2) and for best straight line stability my thought is that a car that is level to the ground would be the most stable, all other things being equal. I am defining level as a car with the same ground clearance at the front edge of the rocker panel to the ground and at the rear edge of the rocker panel to the ground. I am thinking that with stiffer rear springs I may need to bring the front of the car up a bit to level it. Hence the ride height question...
 
Dana67Dart said:
1 3/8" ?????? Where is that being measured from?
Click to expand...
The FSM lists two measurements to determine ride height.
A, from the bottom of the adjusting lever to the ground
B, from the bottom of the lower ball joint to the ground
The 1 3/8 is the result of A - B
 
The factory numbers are realistic. Bottom line is it is not specific other than factory tire size, and only sets the height based on the A and B measurement. If you follow the A to B with any tire size you will get the optimum set up for suspension angles. No matter if it is a 14” tire or 20” tire. JMO
 
I always set mine "where it looks good" to me.
 
For modern tires, etc. I set up about 1" between the LCA bumper and frame and make sure both sides are equal by measuring from the LCA to the frame (takes out any variance in bumper height). The factory setting will have the front end too high for my tastes and their method is a pain to set up not on an alignment rack.
 
The method of setting ride height spelled out by the FSM completely removes tire height out of the equation, it was specifically designed to.

The FSM essentially sets the angle of the lower control arms. If you change the tire height the car will be higher or lower from the ground, but the suspension remains at the same angles and the distances from the control arms to the bump stops remain the same. The suspension geometry is what the FSM spec’d.

Now, is the FSM spec still relevant for you? Depends on two things primarily- whether or not you use radial tires and what size torsion bars you run. And then of course you should also consider how you’re using the car, as always.

If you run radials, the FSM spec is no longer ideal. The control arm angles at ride height set how your caster/camber curves start out, and those curves are better suited for bias plys using the stock configuration. If you run radials you want negative camber gain for best handling, and that’s not what you get with the factory ride height specs.

You can get negative camber gain if you set the ride height so that the angle of the control arms is almost parallel to the ground. That represents and significant drop in ride height though, basically it makes A-B zero. And in order to pull that off you also need larger torsion bars. And depending on how big your torsion bars are, you also need to shorten the lower bump stop and raise the upper bump stop to re-center the range of travel.

Now, if maximum handling isn’t your primary goal, then you don’t need to do all that. But you also don’t need to use the FSM spec, as long as you leave yourself enough suspension travel for the size of the torsion bars you’re running. If you’re running stock torsion bars you better stick close to the FSM spec or you’ll bottom the suspension out all the time. If you run larger diameter bars than stock, then you can lower the car some and improve your suspension geometry and handling.

One thing I would NOT do, regardless the use of the car, is raise it up higher than the FSM spec. The suspension geometry goes to hell if you do that, so unless you’re trying to make your car a 4x4 I’d set it at the FSM spec or lower. If all you’re worried about is straight line stability then the rake only matters as much as it effects your caster. If you can get good positive caster it doesn’t matter if there’s rake for straight line. Now of course for turning stability you’d want your roll centers at close to the same height.
 
Last edited:
Ha! I set my ride height on my 68 using the factory method. Then watched the alignment tech measure from his rack to the left and right wheel lip opening. Old school, not knowing Mopars.

I have .920 T bars and feel I can run with less suspension bumper clearance so I readjusted later. (Knowing it would affect alignment) I also cut 1/2" of rubber from the rectangular-shaped bumper to add clearance before bottoming. Eventually I'll move these "light" t-bar to my /6 Valiant and source heavier bars for the cuda.

A car with a slight nose-down attitude is more aerodynamic thsn a nose-high or level car. This per the Direct Connection chassis manual.
 
thanks for all of the informative replies, great information.

I do have a question for 72bluNblu

what do you mean by "negative camber gain"
I understand negative camber to be the top inside edges of the tires are tipped in towards the center of the car.
and that negative camber can be achieved in the normal alignment process. So how is leveling the control arm to achieve negative camber better?
I appreciate all that you wrote and understand most of it but not this one statement.

thanks
 
my68barracuda said:
thanks for all of the informative replies, great information.

I do have a question for 72bluNblu

what do you mean by "negative camber gain"
I understand negative camber to be the top inside edges of the tires are tipped in towards the center of the car.
and that negative camber can be achieved in the normal alignment process. So how is leveling the control arm to achieve negative camber better?
I appreciate all that you wrote and understand most of it but not this one statement.

thanks
Click to expand...

He`s probly got a better answer, but have you ever seen a mopar w/ the wheels leaning in , during a wheely ? Its what they do.
Main reason I butted in , is , I am curious what ur front fender heigth is measured at the center of the fender , in the static position .
And anyone elses -----------------
 
my68barracuda said:
thanks for all of the informative replies, great information.

I do have a question for 72bluNblu

what do you mean by "negative camber gain"
I understand negative camber to be the top inside edges of the tires are tipped in towards the center of the car.
and that negative camber can be achieved in the normal alignment process. So how is leveling the control arm to achieve negative camber better?
I appreciate all that you wrote and understand most of it but not this one statement.

thanks
Click to expand...

Wheel alignment numbers are constantly changing as the suspension travels up and down. The alignment you have set is called the static alignment. But the wheels travel in an arc as they move up and down because the control arms are a constant length.

How those alignment numbers change depend on your suspension geometry and are called the camber and caster curves. Toe change through the travel arc is typically called bump steer.

Radials usually perform better if the camber becomes more negative as the suspension is compressed, the loaded wheel tips in at the top to counter the movement caused by car pushing it outward, so the tire patch stays planted.

When the control arms are close to parallel at ride height they’re at the middle of the travel arc which means under compression the camber becomes more negative, giving better handling.

This article is about the FMJ spindles, but it talks about the suspension geometry and lists actual number for the curves. The posted number are actually for a car lowered about 1”, it’s noted on the pictures but it’s easy to miss.

https://www.hotrod.com/articles/mopp-0503-swapping-a-and-b-disc-brake-spindles/
famous bob said:
He`s probly got a better answer, but have you ever seen a mopar w/ the wheels leaning in , during a wheely ? Its what they do.
Main reason I butted in , is , I am curious what ur front fender heigth is measured at the center of the fender , in the static position .
And anyone elses -----------------
Click to expand...

Uh yeah that’s wrong. With the wheels off the ground the suspension is at full extension, which tips the tops of the wheel out. Which is positive camber, not negative. Again you can see those numbers in the above article.
 
Consider this and base it on the sum of the parts used!

The factory designed parts were put in the optimum operating position based on the simple A/B measurement. This in turn allowed for the proper alignment procedure to happen. The upper/lower bumps are basically centered in the operation range. While this was a simple basic setup, times have changed with wider taller wheel/tire combos and such. Base your approach on the sum of parts used for your application! If full stock and taller tire, stay close to factory. If full custom then base it on such. Drop or raise the front then bump stops and more will need to be modded.
 
72bluNblu said:
Wheel alignment numbers are constantly changing as the suspension travels up and down. The alignment you have set is called the static alignment. But the wheels travel in an arc as they move up and down because the control arms are a constant length.

How those alignment numbers change depend on your suspension geometry and are called the camber and caster curves. Toe change through the travel arc is typically called bump steer.

Radials usually perform better if the camber becomes more negative as the suspension is compressed, the loaded wheel tips in at the top to counter the movement caused by car pushing it outward, so the tire patch stays planted.

When the control arms are close to parallel at ride height they’re at the middle of the travel arc which means under compression the camber becomes more negative, giving better handling.

This article is about the FMJ spindles, but it talks about the suspension geometry and lists actual number for the curves. The posted number are actually for a car lowered about 1”, it’s noted on the pictures but it’s easy to miss.

https://www.hotrod.com/articles/mopp-0503-swapping-a-and-b-disc-brake-spindles/


Uh yeah that’s wrong. With the wheels off the ground the suspension is at full extension, which tips the tops of the wheel out. Which is positive camber, not negative. Again you can see those numbers in the above article.
Click to expand...

This and 100% of stock suspended mopars says it all.

thumbnail - Copy (2).jpg
 
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