Front End Alignment Specs vs Behavior (Return to Center)

basstrix · Oct 10, 2024

After rebuilding the front end and performing the alignment, the steering wheel does not return to center. The wheel returns partially and then will hold steady. I didn't think to check it in both directions, so at this point, I can say for certain that it does this on a right turn. Which of these parameters might be responsible for this partial return to center behavior?

L-Camber: -0.2
L-Caster: +2.8

R-Camber: -0.8
R-Caster: +3.0

The caster values may be a tiny bit off because I only eyeballed the turn plates...I'll square them up with the laser this weekend and re-check, but I don't expect any change in Camber. It's also possible I have excess preload on the steering box....I was trying to eliminate play and tightened it a bit....but that was a few months ago and this return seems worse than before the rebuild. I've also read that the idler can play a role...the replacement matched up with the old one, so I'm thinking that is unlikely.

bucketlist fastback · Oct 10, 2024

Positive caster is needed. Search this website.. guys have to go well out of normal specifications to get proper return to center steer.

Bentworker · Oct 10, 2024

basstrix said:
After rebuilding the front end and performing the alignment, the steering wheel does not return to center. The wheel returns partially and then will hold steady. I didn't think to check it in both directions, so at this point, I can say for certain that it does this on a right turn. Which of these parameters might be responsible for this partial return to center behavior?

L-Camber: -0.2
L-Caster: +2.8

R-Camber: -0.8
R-Caster: +3.0

The caster values may be a tiny bit off because I only eyeballed the turn plates...I'll square them up with the laser this weekend and re-check, but I don't expect any change in Camber. It's also possible I have excess preload on the steering box....I was trying to eliminate play and tightened it a bit....but that was a few months ago and this return seems worse than before the rebuild. I've also read that the idler can play a role...the replacement matched up with the old one, so I'm thinking that is unlikely.

Just to be positive you are defining positive caster as the lower ball joint being forward and the upper ball joint being rearward?

basstrix · Oct 10, 2024

Bentworker said:
Just to be positive you are defining positive caster as the lower ball joint being forward and the upper ball joint being rearward?

Of course.

Bentworker · Oct 10, 2024

I’d go with your suspicion of the steering box, and the idler arm bushing. I thought Opentracker was making a roller idler for 71-73s

Ron Tanzi · Oct 11, 2024

The best settings for alignment (with a stock suspension) I found is to use +2* positive caster and -.50* camber. These settings give me good straight line stability and steering wheel return to center. This has been my alignment setup for many years. When I used the stock factory alignment specifications my car handled terrible. I found this alignment information in Mustang and Fords magazine a very long time ago. The factory specs were intended for bias ply tires. I have experienced no excess front tire wear issues with these specs either.

Ron

bucketlist fastback · Oct 11, 2024

Ron Tanzi said:
The best settings for alignment (with a stock suspension) I found is to use +2* positive caster and -.50* camber. These settings give me good straight line stability and steering wheel return to center. This has been my alignment setup for many years. When I used the stock factory alignment specifications my car handled terrible. I found this alignment information in Mustang and Fords magazine a very long time ago. The factory specs were intended for bias ply tires. I have experienced no excess front tire wear issues with these specs either.

Ron

Yes, that is precisely what I’m talking about. I work in a heavy truck shop and sometimes they have to use wedges under the I-beams to get that positive caster.

Stanglover · Oct 11, 2024

I currently have 3 deg pos caster and I'd like to put more in as I feel I need to steer the car back to straight ahead. As far as I know, there are shims that can be used, but custom upper control arms are the better way. 3 degrees was as much as my 'guy' could get without stressing the components.
These are the specs that Opentracker post for Radial tires.

basstrix · Oct 11, 2024

Stanglover said:
I currently have 3 deg pos caster and I'd like to put more in as I feel I need to steer the car back to straight ahead. As far as I know, there are shims that can be used, but custom upper control arms are the better way. 3 degrees was as much as my 'guy' could get without stressing the components.
These are the specs that Opentracker post for Radial tires.

Thanks, this is the type of feedback I'm looking for. These are the specs that I've recorded from various sources. The top 3 rows were from Opentracker. Mine was set at -0.5 Camber, +3.2 Caster prior to taking it off the turn plates. I've got it back on the plates and will bring it back to where I had it before the test drive.

basstrix · Oct 11, 2024

Ron Tanzi said:
The best settings for alignment (with a stock suspension) I found is to use +2* positive caster and -.50* camber. These settings give me good straight line stability and steering wheel return to center. This has been my alignment setup for many years. When I used the stock factory alignment specifications my car handled terrible. I found this alignment information in Mustang and Fords magazine a very long time ago. The factory specs were intended for bias ply tires. I have experienced no excess front tire wear issues with these specs either.

Ron

Very good info. Mine is tracking straight and stable, it's just not returning all the way back to center. Sometimes, memory plays tricks, but it seems like it returned better before all the new parts and the additional caster. Prior to taking it off of the turn plates, both sides were set to +3.2 caster and -0.5 camber.

Do you have manual or power steering? Mine's power. I may put the old idler arm back on. It has no play...but is missing the dust seals. The new idler was very stiff when installed....I'll have to take it apart to check now that's is been driven a little bit.

rcadd1ct · Oct 11, 2024

Bentworker said:
I’d go with your suspicion of the steering box, and the idler arm bushing. I thought Opentracker was making a roller idler for 71-73s

Mine didn’t want to return with 4 caster due to the steering box being tightened to remove slop.

Went to a lares quick ratio and open tracker roller idler and it is perfect

Using the street performance specs

https://opentrackerracing.com/tech-info/

basstrix · Oct 11, 2024

@Sheriff41 I tried to IM you but the system wouldn't let me. If memory serves, you've done a bit of alignment work?

Sheriff41 · Oct 11, 2024

@basstrix , My days of doing front end alignments are more decades ago than I like to think about. The tools and technology have advanced since then but the geometry remains the same. We all know caster is set to keep the car going straight down the road and ease steering effort. Caster should be sufficiently set for the steering to self-center. Either something in the suspension is too tight to allow the self-centering or there is not enough caster setting to aid this affect. We used to use shims placed behind the UCA shaft bolts to get additional caster angle.

Your camber is in range but I'm surprised your +3.2° is not working for you. Too much positive caster increases steering effort and would be noticeable. As @Stanglover mentioned above, the custom UCA available really aid caster setting for modern tires (different rolling resistance than old belted tires our cars came with). Larger wheels and tires can change the geometry for alignment settings slightly. What size tires are you running on the front? Significantly different from the stock offset and diameter?

basstrix · Oct 11, 2024

Sheriff41 said:
@basstrix , My days of doing front end alignments are more decades ago than I like to think about. The tools and technology have advanced since then but the geometry remains the same. We all know caster is set to keep the car going straight down the road and ease steering effort. Caster should be sufficiently set for the steering to self-center. Either something in the suspension is too tight to allow the self-centering or there is not enough caster setting to aid this affect. We used to use shims placed behind the UCA shaft bolts to get additional caster angle.

Your camber is in range but I'm surprised your +3.2° is not working for you. Too much positive caster increases steering effort and would be noticeable. As @Stanglover mentioned above, the custom UCA available really aid caster setting for modern tires (different rolling resistance than old belted tires our cars came with). Larger wheels and tires can change the geometry for alignment settings slightly. What size tires are you running on the front? Significantly different from the stock offset and diameter?

Thanks for your input. I'm using a Longacre digital gauge and their bracket that registers on the wheel. The front wheels are on turn plates, which are on a set of crib stands that have rollers attached. The rollers let the wheels move laterally with the idea of helping it to settle after being jacked up or making an adjustment. I use a self leveling laser to make sure the front tire is parallel to the rear when the turn plate is at zero.

My front tires are very stock-ish size-wise. Fronts are 215/70/15, Rear 255/60/15. Nothing remarkable...just a simple classic stance.

I think I'll tweak the settings to get back to my intended values (before the test drive/settling in), then drive it. After that I'll probably swap out the Idler, and next, back off the adjuster on the sector shaft....

One last question for you, Chuck, is it common to get some settling/changes in adjustment after driving? I think my setup is less than ideal, where an alignment rack is much better suited to eliminating variation due to settling and the like.

Sheriff41 · Oct 11, 2024

basstrix said:
Thanks for your input. I'm using a Longacre digital gauge and their bracket that registers on the wheel. The front wheels are on turn plates, which are on a set of crib stands that have rollers attached. The rollers let the wheels move laterally with the idea of helping it to settle after being jacked up or making an adjustment. I use a self leveling laser to make sure the front tire is parallel to the rear when the turn plate is at zero.

My front tires are very stock-ish size-wise. Fronts are 215/70/15, Rear 255/60/15. Nothing remarkable...just a simple classic stance.

I think I'll tweak the settings to get back to my intended values (before the test drive/settling in), then drive it. After that I'll probably swap out the Idler, and next, back off the adjuster on the sector shaft....

One last question for you, Chuck, is it common to get some settling/changes in adjustment after driving? I think my setup is less than ideal, where an alignment rack is much better suited to eliminating variation due to settling and the like.

Yep, I don't see anything out of the ordinary. Yes, you may get a slight change in settings once the car is driven, but they should be negligible.

Your setup is probably fine, though you do need to make sure your plates and stands are all four level with each other.

There is an art to performing alignments. I learned from an old mechanic that had been doing alignments for years using a Bear alignment rack. I probably learned a small fraction of what he knew about alignments.

rcadd1ct · Oct 11, 2024

I had issues getting repeatable results at first

Come to find out the drought dropped one corner of the garage 3/4”

So when I drove in it never was the same.

Now I know that I have spots on the floor I have shims to land on and I verify every time I align it.

I started with all the quick truck stuff but their levels timed out with me doing everything myself so I went with the longacre and the car on ramps on all 4 corners so I can work on the car.

Pain to get set back up after an adjustment, but it is working for me now.

Ron Tanzi · Oct 12, 2024

basstrix said:
Very good info. Mine is tracking straight and stable, it's just not returning all the way back to center. Sometimes, memory plays tricks, but it seems like it returned better before all the new parts and the additional caster. Prior to taking it off of the turn plates, both sides were set to +3.2 caster and -0.5 camber.

Do you have manual or power steering? Mine's power. I may put the old idler arm back on. It has no play...but is missing the dust seals. The new idler was very stiff when installed....I'll have to take it apart to check now that's is been driven a little bit.

I have variable rate power steering with the stock Saginaw box.

Ron

cjstaci · Oct 13, 2024

When I rebuilt my front suspension, I used shims for the uca, as I recall, the alignment shop was able to get 4 degrees of caster. Camber was set at 1 degree and 1/8” toe in. The tires are 245/60/15 radial ta’s. It did increase the steering effort but it drives straight on a flat road. I do have a little bit of play, probably in the steering box.
Since you tightened your steering gear, as long as there’s no binding it should be okay. If your steering returns to center on right turns but not left turns, could possibly be an internal steering gear issue.

basstrix · Oct 13, 2024

cjstaci said:
When I rebuilt my front suspension, I used shims for the uca, as I recall, the alignment shop was able to get 4 degrees of caster. Camber was set at 1 degree and 1/8” toe in. The tires are 245/60/15 radial ta’s. It did increase the steering effort but it drives straight on a flat road. I do have a little bit of play, probably in the steering box.
Since you tightened your steering gear, as long as there’s no binding it should be okay. If your steering returns to center on right turns but not left turns, could possibly be an internal steering gear issue.

I swapped out the new Idler Arm for the old one. The idler was very difficult to turn at the joint attaching to the Center Link. The old Idler has bearings/bushings on both ends....I installed in when I rebuilt the front end back in the 80's...it's much easier to move and still tight. Hopefully that will do the trick. Will know later today.

Stanglover · Oct 13, 2024

basstrix said:
I swapped out the new Idler Arm for the old one. The idler was very difficult to turn at the joint attaching to the Center Link. The old Idler has bearings/bushings on both ends....I installed in when I rebuilt the front end back in the 80's...it's much easier to move and still tight. Hopefully that will do the trick. Will know later today.

Just curious, what brand / make idler arm did you put in there?
The geometry of some repops may not be as the original and if so, that will undoubtedly cause problems. That could be what is causing some of your issue.
Here's a sketch I did to illustrate what I mean. Sorry, this copy is not very clear.
The part I put in my car was the Rare Parts brand (from NPD) and while it may look different the geometry is the same and I have no issues with steering in that regard.

Front End Alignment Specs vs Behavior (Return to Center)

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