Caster & Camber VS Height

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fjr

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I have a 1965 Barracuda that I've upgraded from 9" drums to 74 Duster disc brakes and used urethane UCA bushings from Just Suspensions. I don't have power steering. Having read up on the alignment advice here at FABO and at slantsix.org, I want to my car to have:
  • Camber: -0.25° L / -0.25° R
  • Caster: +1.25° L / +1.75° R
  • Toe-In: 1/8”

I've been having a hard time getting the local alignment shops to adjust to my specs. I know that, as the torsion bars are adjusted to raise the ride height, camber becomes more negative but, on the alignment rack, raising the height seemed to make camber more positive. The front is adjusted a bit low (much less than the 2" factory spec) at this time.

I bought the Moog PN 7103 offset bushing kit to get more caster & camber adjustment but I'm wondering if the real problem is that the alignment mechanics don't understand a-body suspensions. I have a new idler & pitman arm to install this month and would rather not replace my UCA bushings unless necessary.

Can I get -0.25° camber and +1.25° positive caster with my already-installed concentric urethane UCA bushings with just a bit more ride height?
 
If you adjust with 1/2* less camber on the left, it will pull to the left on modern roads. Used to be the roads were crowned a lot more than they are now. I would adjust caster evenly.

You might get a little more camber raising the ride height. Trying to "adjust" caster with the front ride height is futile. Lowering the car from the rear however, would have much more of an effect, but I don't recommend either, unless you have air shocks in the rear that are pumped all the way up.

You probably hit the nail on the head with the mechanics not know how to do it. All they are used to now are cars where they can "set the toe and let it go" and most still don't get that right.
 
IIRC, the 1/2° difference in caster was advised by alignment mechanics. My FSM specifies +0.25° more camber on the left (preferred camber: +0.50 L & +0.25 R),I think caster should be the same L & R too but my last alignment ended up with positive camber and negative caster and was out enough to cause major shoulder wear on my tires.

I was hoping that if I could get some negative camber with the ride height adjustment, I might have adjustment left in the eccentric cams to get a little positive caster.
 
Jacking the ride height up in the front will increase camber. It will have little to no effect on caster, because the pivot point is in the rear. If you adjust the rear ride height, that would have a much more profound effect on caster, since you make the pivot point in the front, but again, the ride height is not an adjustment for caster. You need to find someone who knows alignments. I could align that car in 30 minutes to those specs provided nothing is bent and it's not been in an accident. At the very most, it MIGHT need the offset bushings, but that's not a huge amount of caster you want, so I doubt it.
 
RustyRatRod said:
You probably hit the nail on the head with the mechanics not know how to do it. All they are used to now are cars where they can "set the toe and let it go" and most still don't get that right.
Click to expand...

Alignment shops usually rely on some sort of computerized system based off of factory specs. The way it works is you set the car up on the rack with turn plates and sensors. Then you input year, make, model etc. and the specs come up on a screen. Adjust the components to proper range and test drive.

Keep in mind these specs are based on the assumption that the car has all the original equipment and tires and is set to factory ride height. And, though I am not 100% sure on this, most shops probably don't have accurate information in their alignment system for anything before the '80s. They likely won't do it because they don't want the liability of a 'custom' or guesstimate setting which may differ from whatever info they can find.

Could they do it the way you want? Probably but again, no one wants the liability.

There are tools/methods to do it at home.
 
I did alignments for almost 20 years. We stood behind everything I did. I strayed from specs all the time. You cannot align based on specs alone. You have to align based on tire wear. That's why a follow up checkup in about 1000 miles is so important. So that the alignment can be zoomed in in if necessary. We always include that in the original alignment price and THAT is the only way we would not stand behind it, is if the customer never brought it back for that checkup.
 
Increasing ride height increases camber. The higher you go, the more positive the camber will get. Lowering the car decreases camber- once you're in negative camber territory, lowering the car will make the camber more negative.

Which is one of the reasons why our torsion bar suspension is great for setting up a performance handling car. Lowering the car with the torsion bars also gets you more negative camber, and that's exactly what you want.

As far as the alignment shops, good luck. A lot of the chain shops will not align to anything other than what's in their computer, and what's in their computer is the factory specs for bias ply tires. You may be able to appeal to reason by explaining that the specs in their computer were for bias ply tires and will be horrible for the radials on your car, but only the "technicians" with half a brain will understand that. You may have to find an independent shop.

If they get squirrely you can sometimes talk them into putting a modern car into the computer. Unfortunately, most modern cars run more negative camber and a TON of positive caster. You can tell them to just get as close to that as they can get, but if you look at the specs for a SRT8 Challenger you'll see what I mean. The minimum camber specs will work good, but you'll never get anywhere near those caster specs without adjustable UCA's, and you won't want them if you have manual steering. The only good news is with the stock UCA's you probably won't get more than +3 caster anyway, and that would be fine.

SRT8


FRONT WHEEL ALIGNMENT
PREFERRED SETTING
ACCEPTABLE RANGE
CAMBER - LEFT
−1.05°
−1.60° to −0.50°
CAMBER - RIGHT
−1.35°
−1.90° to −0.80°
CROSS-CAMBER * (Maximum side-to-side difference)
+0.30°
−0.25° to +0.85°
CASTER - LEFT
+8.30°
+7.30° to +9.30°
CASTER - RIGHT
+9.00°
+8.00° to +10.00°
CROSS-CASTER * (Maximum side-to-side difference)
−0.70°
−1.30° to −0.10°
TOE - TOTAL**
+0.20°
0.00° to +0.40°
 
Most alignment guys don't know enough about the machines....but you can turn the spec comparison OFF so that the numbers are white instead of green or red. That's how I normally did it.
 
RRR hit the nail on the head. These new computer machines give you a print out with green and red and all the cutsie numbers that to you and I don't mean squat. Also said above it's the shops way of showing the customer "See all adjustments are in the green so all is good".
I also agree to keep the caster as close as possible as that 1/2* difference will cause the car to pull. As RRR said we did use caster to compensate for road crown back when they would crown the road to the right for water run off. Some states still do it and can be clearly seen with a trained eye.
So all that aside, You are setting the car up to handle,thus going negative on the camber and getting as much positive caster as the cams allow. I have RRR beat by a few years. I started using a John Beam(NOT Jim Beam )Vis-u-liner back in 1972 when these cars were the latest thing on the market. I still use turn tables,trammel bar, and bubble gauges to do alignments today. You have to be at least 60 years old to know what a trammel bar is (or close to it ! ). Keep checking around you may find a grey beard that will know what you want and how to do it ! Good luck
 
That's pretty cool. The very first alignment I did was about 1976. We had the caster/camber bubble gauge and a toe stick (trammel bar). That was all. In 1980 when I was in the 10th grade, I was able to take auto shop. The machine we had there was actually very cutting edge for the time. It was a computerized Sun alignment machine with the string set that attached the front and rear heads and the two fronts. I actually prefer the old stuff, because unlike the computerized machines, you actually see and know what you are doing much more so than with a computer. It is all basic grammar school geometry, but using the computer, it actually does a lot for you, rather than you figuring it out yourself. I always loved doing alignments. I have thought about finding an old hunter A111 and setting up out here and advertising locally by word of mouth that I can do classic car alignments. I may still do it if things pan out.
 
The shops I've been dealing with don't have a problem with using a custom alignment spec. The problem is that they don't seem to understand the alignment procedure for an a-body even though I bring my FSM, which increases the time the car is on the rack.

The only time they got the alignment around where I wanted it was when the LCAs were pretty much riding on the bumpers. It was low enough for rough pavement to put a dent in my oil pan so we had to raise it up to where is it now (~ 8-3/4" from adjusting blade to floor, P195/75R14 tires).

It looks like I misunderstood how camber changes with height and installing the offset bushing kit is pretty much unavoidable to get the alignment I want.

My car has the slant six stock torsion bars and a 1-1/8" Addco front stabilizer bar. The car is mainly highway-driven and is never raced. Any advice about what would be good height setting so that my car is low enough to rarely bottom-out on bumps?
 
I would set it to stock ride height. Either one of three things is happening. Either the alignment shops you've taken it to haven't a clue how to adjust it, or you have some bad parts, such as control arm bushings, for example, or it has been wrecked at one point in time and not repaired correctly. I tend to think it is the first problem from your description. Most alignment shops nowadays look at older cars as a waste of time because they actually have to make caster/camber adjustments, instead of only setting the toe, so no one every really learns how to do it correctly. It's becoming a lost art of sorts.
 
fjr said:
My car has the slant six stock torsion bars and a 1-1/8" Addco front stabilizer bar. The car is mainly highway-driven and is never raced. Any advice about what would be good height setting so that my car is low enough to rarely bottom-out on bumps?
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With the slant 6 torsion bars, if you go much lower than the stock ride height you'll bottom out the suspension frequently. If you want to lower the car any from stock, you need to increase the torsion bar size to reduce the amount of suspension travel you need to have.
 
As far as I know, the car has never been hit. Previous alignments with the stock 9" drum system never reported any issues and the car steered well afterwards. The bushings are all new as I got a front-end rebuild kit with urethane bushings from Just Suspensions.

By stock ride height, the spec calls for 2” ± 1/8” side to side (bottom of adjustment blade to bottom of steering knuckle arm). If I understand this correctly, the bottom of the adjusting blade is the lowest part of the torsion bar anchor in the lower control arm. The bottom of the steering knuckle arm would be the lowest part of the lower ball joint at the spindle. Mechanics seem to have trouble with this, especially since they need to use a straight-edge to span open area of the alignment rack. My 1975 FSM shows the ride height spec as being 10-15/16” – torsion bar anchor to ground for 1975 a-bodies.
 
Good informational thread.Haven't done an alignment,in twenty years. Always liked the spindle mount style bubble gauges here. How are the local circle track racers,getting theirs done? Those are always done ,to a non factory spec.
 
Here's an alignment chart you may want to consider. I went with + 2º caster, - ..75º camber and 1/16" toe-in. I got greater steering effort (ps), less self-centering action, and sharper turn-in response.I set the ride height at the lower limit of factory tolerance.
 

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Awesome thread, great info...

I just went through a very similar situation myself.

Just bought a 72 Valiant. The guy I bought it from had lowered the front end via the torsion bars and it had an awesome stance. He had 14" AR rims for it but said they were rubbing on the control arms and needed a wheel alignment so that they would fit. In my ignorance I believed him, took it to a local shop for the alignment. They had a hard time finding the specs for their machine but managed to find them but said there was no way they could get it in spec without cranking the torsion bars back up (replaced ball joints and pitman arm as well)

It handles and steers great (for all stock parts) but now the front end sits higher than the back and looks goofy (and the front rims still rub on the control arm...grrr)

Any suggestions? I have thought about raising up the rear to level the car back out but would be great if I could lower the front a bit, maybe just not as much as it was but I dont know much about alignments and I dont think there are many shops that do around here either
 
Duece said:
Awesome thread, great info...

I just went through a very similar situation myself.

Just bought a 72 Valiant. The guy I bought it from had lowered the front end via the torsion bars and it had an awesome stance. He had 14" AR rims for it but said they were rubbing on the control arms and needed a wheel alignment so that they would fit. In my ignorance I believed him, took it to a local shop for the alignment. They had a hard time finding the specs for their machine but managed to find them but said there was no way they could get it in spec without cranking the torsion bars back up (replaced ball joints and pitman arm as well)

It handles and steers great (for all stock parts) but now the front end sits higher than the back and looks goofy (and the front rims still rub on the control arm...grrr)

Any suggestions? I have thought about raising up the rear to level the car back out but would be great if I could lower the front a bit, maybe just not as much as it was but I dont know much about alignments and I dont think there are many shops that do around here either
Click to expand...

What alignment specs were they using? Usually if it's lowered and they can't get it in spec it means they're using the stock specs, which are incorrect for radials. You want something more like the skosh chart posted above, say -.5* camber, +3 caster and around 1/8 to 1/16 toe in.

You still may need to install a set of offset UCA bushings though to get both the camber and caster to those specs. Plus, if you lower the car a bunch you'll need larger torsion bars to keep from bottoming the suspension. Most of the stock torsion bars can barely do that at the stock ride height.
 
I still got this in my garage. Saved it from someones scrapmetal bin years ago;

IMG_0598.jpg


IMG_0595.jpg
 
72bluNblu said:
What alignment specs were they using? Usually if it's lowered and they can't get it in spec it means they're using the stock specs, which are incorrect for radials. You want something more like the skosh chart posted above, say -.5* camber, +3 caster and around 1/8 to 1/16 toe in.

You still may need to install a set of offset UCA bushings though to get both the camber and caster to those specs. Plus, if you lower the car a bunch you'll need larger torsion bars to keep from bottoming the suspension. Most of the stock torsion bars can barely do that at the stock ride height.
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They were using the stock specs, so that would explain it.
My plan is to flip the drum brakes for discs down the road but I have an engine/tranny re-build that I want to do first. When I change over to discs perhaps I will look at larger torsion bars and an alignment tech that knows what the hell he is doing.

Any cheap/easy ideas on how to get the back end up an inch or two to level it out in the mean time?
 
Duece said:
Any cheap/easy ideas on how to get the back end up an inch or two to level it out in the mean time?
Click to expand...

This might not be for everybody but it worked well for me. I junked out a Duster / Demon for parts.

Tore down my original 67 spring packs, AND the junker, and "combined" them

I used the longest leafs out of the two, except for the "eye" leafs which are original

If I remember, mine now has 1 more leaf than factory. It stiffened it right up, and set it "exactly" where I want it.

Before I tore it down for paint last fall. It was supposed to be painted early this spring.............

Those are 'Stang Buttitt 17" on the rear, 14's on front

 
when you raise the front end the upper A arm goes down forcing the upper ball joint forward and that will reduce castor.
..or do i have that backward?
 
It does, but I'm not sure it balances itself out or gets behind through its travel. A taller front tire would gain you caster with all else being the same. A bodies have a lot of antidive built into the upper arm design.
 
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