Front End Alignment Specs vs Behavior (Return to Center)

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.

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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?

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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

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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.

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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

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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

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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?

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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.

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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.

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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.

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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.

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