Ride height setting confusion

[1973dust]

I'm trying to get the ride height and alignment properly set after doing a full front-end rebuild over the winter. I do have a factory service manual and, assuming I am really measuring at the correct locations, I'm currently at 1 3/4" which is 1/8" lower than stock. I am measuring to the extreme lower point of the ball joint and the "rib" directly underneath the torsion bar socket on the adjuster. I think the front-end looks 4x4 height currently. I'm at 26 3/4" from the floor to the fender opening and the k-frame is 7 1/2" off the floor. What is really confusing me is that I only have about 1/2" clearance to the LCA bump-stop which, I would think, should be much greater at my current ride height. If I lower the car to the height that looks right to me, it's practically sitting on the bump-stop. I'm hoping someone can give me an idea what I am doing wrong. FYI, I do intend to shorten the sway-bar links and bolts once I get the ride height ironed out.

 

[toolmanmike]

I adjust mine to my liking. Bounce it a few times and re-measure at the top of the wheel openings then take it in for an alignment.

 

[mopowers]

Set it where you want it. You can always cut down the bump stops a little.

 

[RustyRatRod]

My service manual gives the spec between the bump stops and the frame where they make contact. But adjust to your liking. A small bit at the time until it sits level but where you want it.

 

[toolmanmike]

I kind of like the way they sit.

 

[1973dust]

So these cars were as high as mine is when new? If so, I would think they were always using the bump-stops as part of the suspension with factory torsion bars. I've just installed 1.03 PST's and have read on here that I would still want about 1" clearance at ride height. I'll definitely have to shorten the bumpers when I lower it down to where I would like. I assume you all agree that the car currently looks too high.

 

[1973dust]

I kind of like the way they sit.

View attachment 1716062891

View attachment 1716062892

Yes, I love the stance of both of your cars. Do I remember right that you have 15's on the rear and 14's on the front of the blue car? My front tires are taller than I would prefer at about 26" but they will have to do for now.

 

[toolmanmike]

Yes, I love the stance of both of your cars. Do I remember right that you have 15's on the rear and 14's on the front of the blue car? My front tires are taller than I would prefer at about 26" but they will have to do for now.

The Swinger has 14's and 15's. The 66 are both 15's with those wheels.

 

[toolmanmike]

Yes, I love the stance of both of your cars. Do I remember right that you have 15's on the rear and 14's on the front of the blue car? My front tires are taller than I would prefer at about 26" but they will have to do for now.

I would lower it down a bit at a time until you get where it looks good.

 

[AJ/FormS]

The factory height will set the lower control arm in the center of it's camber curve. When it is there, (which is nearly level from the rear, level being determined by an imaginary line drawn between the center of the T-bar and the center of the LBJ) you will have the least amount of wandering due to toe-change, as the suspension cycles up or down.
If you have modified any parts or intend to not use the factory alignment settings then your camber curves may no longer be valid.
To find your camber curve, you would have to ask the alignment tech to generate them, and it won't be cheap. Once you have those, they will show you what ride height would likely be best.
But the fact is, that if your wheels are not stock, or more specifically that the offset of the spider is not in the stock location and or the tire is a different diameter than what the car left the factory with, then it will wander anyhow.
So where do you draw the line?
Well let me tell you, lol; after a bunch of alignments (I was an alignment tech with unlimited use of the rack, after hours), The only way I could minimize the wandering was by creeping ever closer to the stock specs.
If you don't spend a lotta time at hiway speeds, this may not be an issue for you. But as for me, I live in a rural area and it's 20 to 30 minutes to the nearest towns and my car was my DD.
The Zerk is Not part of the measurement, you probably know that, and I suppose that what you are calling a rib, is actually the adjusting blade... which would be correct for the factory T-bars....... but may not be with the 1.03s. I know that with 1.03s, I could not use the blades..
I think I started with the LCAs parallel to the road using an imaginary line between the center of the LBJ, and the center of the T-bar, as noted above. This gave me a height of about 6 inches at the K-member, and plenty of room on the bumpstops.
I tried 5.5 but that put the suspension very nearly on the stops and altho it cornered swell there, the ride was too harsh for me. Eventually, I landed on 5.75 at the K. and it's been there for IDK, 18 years or so. Or maybe I went back to 6.0 I forget.
My 68Barracuda has a different spec than the Duster ; at 1.375

 

[Dana67Dart]

Dang my dart sits low in the front. I have about 1/2 " between bumper and the stop.

Front

Rear

 

[Ahoey]

View attachment 1716062869

View attachment 1716062863

View attachment 1716062865
I'm trying to get the ride height and alignment properly set after doing a full front-end rebuild over the winter. I do have a factory service manual and, assuming I am really measuring at the correct locations, I'm currently at 1 3/4" which is 1/8" lower than stock. I am measuring to the extreme lower point of the ball joint and the "rib" directly underneath the torsion bar socket on the adjuster. I think the front-end looks 4x4 height currently. I'm at 26 3/4" from the floor to the fender opening and the k-frame is 7 1/2" off the floor. What is really confusing me is that I only have about 1/2" clearance to the LCA bump-stop which, I would think, should be much greater at my current ride height. If I lower the car to the height that looks right to me, it's practically sitting on the bump-stop. I'm hoping someone can give me an idea what I am doing wrong. FYI, I do intend to shorten the sway-bar links and bolts once I get the ride height ironed out.

Very nice car. I was wondering if you would know the stock rear ride hight for your car.

 

[YY1]

I've never had any ill effects from setting them where I want them (within reason) in over 38 years.

...but you have to tell the alignment guy not to change it from where you have it.

 

[racerjoe]

What size torsion bars do you have? If you have big bar, you can run the car much lower. You will just need a shorter LCA bump stop and a taller one for the UCA. This is common practice on guys running big bars and lowered ride height.

 

[MoparLeo]

Ride height actually it is called suspension height as it is a suspension to ground measurement not a vehicle height. The number is a relationship of lower ball joint to torsion bar pivot height difference.
The ground clearance/fender well filling is based on tire height .
All Factory specs (regardless of whether it is a suspension, engine, etc...) are always based on assumed factory spec'd parts.

 

[1973dust]

What size torsion bars do you have? If you have big bar, you can run the car much lower. You will just need a shorter LCA bump stop and a taller one for the UCA. This is common practice on guys running big bars and lowered ride height.

No idea how I got RustyRatRod's name at the top of your quote but I have 1.03 bars, so yes I will be able to drop the height. I'm just confused why I only have a 1/2" bump-stop clearance with the suspension settings at close to factory height.

 

[1973dust]

Very nice car. I was wondering if you would know the stock rear ride hight for your car.

Thanks, it looks a lot nicer in pics than my amateur paint and bodywork really is. It is currently sitting 27 1/4" from the floor to the center of the rear wheel openings. That is with 235/55R17 rear tires and stock leaf springs from a V8 BBP 1974 Valiant 4-door.

 

[racerjoe]

Thanks, it looks a lot nicer in pics than my amateur paint and bodywork really is. It is currently sitting 27 1/4" from the floor to the center of the rear wheel openings. That is with 235/55R17 rear tires and stock leaf springs from a V8 BBP 1974 Valiant 4-door.

I’m at 24.75” front and 25.5 in the back. 25.5” tires, which is much shorter than yours.

 

[Ahoey]

I’m at 24.75” front and 25.5 in the back. 25.5” tires, which is much shorter than yours.

Thanks for your in put. Want to buy new or rearc originals, car sat for 39 years with a full load of parts in trunk. So she’s got a bit of a saggy bottom. Don’t want to shackle it looks like lame *** punk ****. Would just like to know what the car was bought with

 

[MoparLeo]

Original Factory tire size options depending on engine size:
6.95-14 on a 14 x 4 1/2" wheel = 24.7" Tall
D78-14 on same wheel.
E70-14 0n a 14 x 5 1/2" wheel. = 25.3" Tall

 

[Dana67Dart]

I'm just confused why I only have a 1/2" bump-stop clearance with the suspension settings at close to factory height

That's about what I have.
New video by Dana Nance

 

[1973dust]

That's about what I have.
New video by Dana Nance

Thank you very much! I guess if a picture is worth a thousand words, a video is worth ten thousand. Being able to actually see what is happening was interesting. As you said, it looks like your bump-stop clearance is pretty much identical to mine so I just have to do what everyone has said and lower the car to my liking and shorten the bump-stops as needed. I assume your car is set to near factory ride height?

 

[Dana67Dart]

. I assume your car is set to near factory ride height

56 years ago!

I'm not sure I would cut the stop down.

My theory about the shape of the stop is it is thin at the top and gets fatter.

When the stop first contacts the frame it applies a small amount of force to the frame in a progressive ( I hate that word) fashion, becoming larger till it will no longer compress and the suspension is locked.

If the stop is cut down to the fat part only, the travel will go from movement to stop instantly. Seems hard on the components.

 

[1973dust]

56 years ago!

I'm not sure I would cut the stop down.

My theory about the shape of the stop is it is thin at the top and gets fatter.

When the stop first contacts the frame it applies a small amount of force to the frame in a progressive ( I hate that word) fashion, becoming larger till it will no longer compress and the suspension is locked.

If the stop is cut down to the fat part only, the travel will go from movement to stop instantly. Seems hard on the components.

I will actually make my own tapered stops similar to the factory shape but just shorter. I've got access to similar rubber at work and I can always swap back to the factory height if needed. I agree with you that I'd rather not give up the "progressive" action of the factory style stop. As a side note, are you the original owner of your Dart? If so, that is pretty cool. My dad has a 70 Challenger that he bought new that my son and I are planning to get back on the road in the near future. It really needs a full resto.

 

[72bluNblu]

View attachment 1716062869

View attachment 1716062863

View attachment 1716062865
I'm trying to get the ride height and alignment properly set after doing a full front-end rebuild over the winter. I do have a factory service manual and, assuming I am really measuring at the correct locations, I'm currently at 1 3/4" which is 1/8" lower than stock. I am measuring to the extreme lower point of the ball joint and the "rib" directly underneath the torsion bar socket on the adjuster. I think the front-end looks 4x4 height currently. I'm at 26 3/4" from the floor to the fender opening and the k-frame is 7 1/2" off the floor. What is really confusing me is that I only have about 1/2" clearance to the LCA bump-stop which, I would think, should be much greater at my current ride height. If I lower the car to the height that looks right to me, it's practically sitting on the bump-stop. I'm hoping someone can give me an idea what I am doing wrong. FYI, I do intend to shorten the sway-bar links and bolts once I get the ride height ironed out.

Your setting is pretty close to factory, and yes, they looked like 4x4's. Even in the promotional pictures you can see a lot of the cars were almost nose high. So, you didn't do anything wrong at all. The 1/2" to the factory bump stop is also close to correct, these cars in stock trim used the lower bumpstop quite frequently. It's a progressive bump stop that helped to make up for the ridiculously soft factory torsion bars. Most people with stock set ups don't even realize that they're constantly all over the lower bump stops. A dab of grease on the top of the bump stop and a trip around town will pretty much always show contact with factory settings and bars.

I run my Duster at about 24 7/8" from ground to fender. It's lowered about 2" from factory. Following the factory method for measuring A-B to determine the ride height I'm pretty much at 0. I run an upper bumpstop that's about 2.75" tall, and a lower bump stop that's about 3/8" tall. But I also run the earlier style QA1 LCA's, which aren't as thick and therefore add more clearance. I end up with a little less than 1" of clearance at the bump stop. Which yeah, is probably a bit more than factory. But because I run a short, non-progressive polyurethane bumpstop, I don't want to be using it all the time. I want my suspension to stay off the bump stops, where the factory basically counted on using the bump stops.

The factory height will set the lower control arm in the center of it's camber curve. When it is there, (which is nearly level from the rear, level being determined by an imaginary line drawn between the center of the T-bar and the center of the LBJ) you will have the least amount of wandering due to toe-change, as the suspension cycles up or down.
If you have modified any parts or intend to not use the factory alignment settings then your camber curves may no longer be valid.
To find your camber curve, you would have to ask the alignment tech to generate them, and it won't be cheap. Once you have those, they will show you what ride height would likely be best.
But the fact is, that if your wheels are not stock, or more specifically that the offset of the spider is not in the stock location and or the tire is a different diameter than what the car left the factory with, then it will wander anyhow.
So where do you draw the line?
Well let me tell you, lol; after a bunch of alignments (I was an alignment tech with unlimited use of the rack, after hours), The only way I could minimize the wandering was by creeping ever closer to the stock specs.
If you don't spend a lotta time at hiway speeds, this may not be an issue for you. But as for me, I live in a rural area and it's 20 to 30 minutes to the nearest towns and my car was my DD.
The Zerk is Not part of the measurement, you probably know that, and I suppose that what you are calling a rib, is actually the adjusting blade... which would be correct for the factory T-bars....... but may not be with the 1.03s. I know that with 1.03s, I could not use the blades..
I think I started with the LCAs parallel to the road using an imaginary line between the center of the LBJ, and the center of the T-bar, as noted above. This gave me a height of about 6 inches at the K-member, and plenty of room on the bumpstops.
I tried 5.5 but that put the suspension very nearly on the stops and altho it cornered swell there, the ride was too harsh for me. Eventually, I landed on 5.75 at the K. and it's been there for IDK, 18 years or so. Or maybe I went back to 6.0 I forget.
My 68Barracuda has a different spec than the Duster ; at 1.375

The camber curves are available for a lowered car, they were published for a car lowered 1" from factory buy Bill Reilly. The curves were published in data form in this article, for both the factory 73+ A-body disk spindle and the FMJ spindles. Swapping Disc-Brake Spindles - Mopar Muscle Magazine

The best suspension geometry for the A-body suspension with radial tires comes very close to being when the LCA is parallel to the ground, or A-B = 0. You can actually see this in the tables published in that article. Because the length of the control arms doesn't change, the data points are not going to change substantially. Lowering the car doesn't change the data points, it just means that you're moving along the curve (through the data points) from a different starting spot. Which is important, because if you start from the LCA level to the ground all the upward travel of the suspension adds negative camber, which is exactly what you want for best handling with radial tires. Now, making static camber and caster adjustments does change those curves a little, but really, for the most part you can look at those curves and have a decent idea of what you'll get. If you're setting up for competition the devil is in the details and you'll want to measure your own car, but for most street cars, even ones set up for handling, the general idea of what the curve is doing is just fine.

Now, why is the factory ride heigh the way it is? Well, the factory ride height puts the control arms at an angle. From where the suspension starts at the factory ride height, you get positive camber gain initially, which is better for bias ply's. Which is why it was designed the way it is. But it's not good for radials, which do better for handling with negative camber gain. Fortunately, because torsion bar suspension is very ride height adjustable, we can literally correct for the factory setting the car up for bias ply's just by lowering the car and adjusting the bump stops around the new center point. The best handling for a radial tire equipped A-body ends up being lowered quite a bit from factory.