[xSHAKEandBAKEx]

I was involved in a side swipe on my LT1 impacting the rear quarter panel, door, rocker, and rear wheel.

The car bump steers like crazy, steering feel is uneven side to side with it being lighter to the left , and it just doesn’t feel connected to the pavement especially when making left turns.

After each of my 3 alignments in the last month with totally decent numbers on the sheet when I left, I’d find the left front and back left toe was almost double the value (.10 to .20 or close to) after an alignment check.

[Msquared]

SAI (steering axis inclination) on the rear is...not exactly a thing, I think. It literally only matters up front, where there is actual steering going on; and I think it's only accurately measurable on an alignment rack by moving the steering through a range so the machine can measure the change in camber as steering angle changes. With a non-steering suspension, I don't know how the machine could possibly measure SAI. Now I'm not the Einstein of alignments, so maybe there's a way I don't know about, but I can't imagine what it would be. So I'm guessing a rear "cross-SAI" (a an alignment parameter I've never even heard of before) is a misinterpretation of something. Besides all that, even if a knuckle is in fact jacked, that shouldn't make the alignment change after you leave the shop. It's true that a bent knuckle could throw SAI off, but then it should also throw off rear toe/camber/caster as well. If they were able get those settings into spec and pretty close from one side to the other (the "cross" measurements), then the knuckle probably isn't bent.

My bet is that something wasn't tightened properly, or that a ball joint or bushing somewhere is bad and didn't get replaced as it should have. For example, my neighbor's Jeep Wrangler had to get its entire rear axle/housing replaced after an accident. He asked me to ride in it to hear a noise after he got it back, and it turned out they had loosened the front trailing arm bushing bolts to let the arms swing down for the axle replacement, but they forgot to tighten them again after it was all back together. He had brought it back to them two or three times to find and fix the noise, and they had no clue. I'm a social worker and diagnosed it in 30 seconds and fixed it in five. This shit happens all the time. In your case, I would nut-and-bolt every part of the rear suspension, and anything else they touched. Or I would have a shop do that. I bet something is loose or bad.

[bishopts]

to add to that. ive noticed when im doing alignments that are way out of spec, i will set everything as good as i can get it. then re compensate the alignment heads while its still on the lift. i will usually do this 3 times at minimum before i take it off the lift.
when doing this i will usually notice every re compensation the specs will be off from what they were considered "good" but gradually be closer and closer to not needing adjusment.

[WhiteMale]

Are talking about Caster and SAI is another word for it?

[bishopts]

Originally Posted by WhiteMale

Are talking about Caster and SAI is another word for it?

Caster is the relation of the upper and lower ball joint/mount point in a forward and backward relationship.

SAI is a inward or outward tilt of the wheel in turns that is a result of caster and camber positions.

Caster and camber both have affects on SAI. Its not used in alignments normally because its mostly geometric math related to caster camber and steering angle. And you don't align vehicles with the wheels turned.

[atx_traveler]

rear toe is held with an eccentric. my bet is you need a new bolt since these are TTY and likely to be stretched and not holding.

[Msquared]

To be more clear about SAI's definition, it's the inclination of the steering axis from a frontal view. The axis is defined by the upper and lower points on which the axis turns when the steering wheel is turned. Caster is the angle of that steering axis when viewed from the side. For an old-school double-A-arm suspension, those points are the upper and lower pivot points, and for an old-school strut they are the lower ball joint and the upper strut bearing. For our cars, the lower pivot point is a virtual one. It's defined by extending lines through the two lower lateral links to their intersection point.

As far as I know, most/all cars have some positive SAI (axis leans in toward the center of the car at the top). Some have a lot in order to minimize scrub radius (e.g. 88-96 Corvettes), but it seems like engineers have decided that 6 degrees or less is desirable. The problem with SAI is that it causes a loss of camber as you turn the steering wheel. The tighter you're turning, the more camber you lose. That sucks, but it can be counteracted by caster at a proportion of 1:1 (1 degree of caster counteracts the camber loss of 1 degree of SAI)...to a point. You can't realistically dial in 14 degrees of caster to counteract all the camber loss of the massive SAI in later C4s: all manner of weird things start happening if you try.

Anyway, adding negative camber by moving the top of the strut (or UCA) or moving the lower control arm(s) also increases SAI because that moves the pivot points for the steering axis. Changing camber at the strut:knuckle interface, like our cars do, does not increase SAI. So only some types of camber adjustment affect SAI. Caster does not affect SAI: you can change caster without changing SAI. AFAIK, SAI is measure by moving the steering lock to lock and the alignment machine measures camber change (I assume after it factors in caster).

But again, since SAI literally involves the steering axis, then I don't know why or how anybody would measure it in the rear suspension. There is an axis back there, but since the rear suspension has no active steering, then I don't know if we can really even call a "steering axis." And I definitely don't know why anyone would care! And finally, a changing SAI won't be caused by a bent knuckle. Somethings is moving/changing as you drive. atx_traveler is on to something with the eccentrics. The rear camber is also adjusted with eccentrics. These things suck, and they can move if not really tightened correctly. That's the first place I'd look.

[xSHAKEandBAKEx]

[QUOTE][/QUOTE] Here are my alignment specs.

Apologies, I thought I had them on there but I think my original post got moved. Thank you so much for all of the great information.

The SAI I was referring to was for the front end which feels loose right now to say the least, along side the left overall feel of the car. I’m not getting a lot of feedback from the front left wheel but I can feel everything like I should in the right front wheel.

I didn’t see any wheel impact marks on the front left wheel but the alignment shows how off everything was after the alignment.

I suspect something loose in the rear as well on the wheel that was hit because the toe keeps changing after each alignment by quite a bit where the right side doesn’t change. Also to note, when they set the front toe at .10 and .10, it always comes back at like .18 per side or so for the front wheels after a tank of gas and an alignment re check because I could feel it going out.

[bishopts]

I would take it somewhere else. If you have the ability in your area take it to someone who specializes in alignments.
I had a similar problem with the alignment angles always being different after i aligned a car and it was one of the alignment head brackets for the wheels was slightly bent

[atx_traveler]

Also 2nd the recommendation to take it somewhere else.


The "steering feel is uneven side to side with it being lighter to the left" tells me that your steering angle sensor has a discrepancy with the actual centering of the steering wheel. Either the sensor was not reset to match the center OR your steering wheel is not centered via the tie rods. Is your steering wheel crooked going straight?

[xSHAKEandBAKEx]

Originally Posted by atx_traveler

Also 2nd the recommendation to take it somewhere else.


The "steering feel is uneven side to side with it being lighter to the left" tells me that your steering angle sensor has a discrepancy with the actual centering of the steering wheel. Either the sensor was not reset to match the center OR your steering wheel is not centered via the tie rods. Is your steering wheel crooked going straight?

The last alignment sheet was from the dealer. They reset the sas and recalibrated the sensor after 2 Alingment from the body shop, and the more I drive the worse it got, with the car still feel sloppy to the left but the steering is wheel is crooked to the right now…

The biggest thing I noticed besides the steer angle being off is way more sway in the steering from left to side, softer giving more play to make simple lane changes where the steering before was tight and centered.

[Msquared]

To close one line of inquiry, your SAI in those spec sheets is fine. Cross-SAI is merely the difference between one side and the other, but as mentioned before, that's a function of the other settings. There's no "SAI adjustment," so to speak. From what little I can see online, SAI in the 14ish range is correct for this car. We don't really need to keep discussing that spec.

What I do see is that your left rear toe went from 0.13 to 0.25 between the last two alignments...at least on paper. That may point to slipping toe adjusters (the aforementioned eccentrics). That really needs to be looked at. The spec on torquing that adjuster bolt is way more than most people think. Did I mention that eccentrics for alignment adjusters are the spawn of Satan?

The person that commented on steering angle sensor (SAS) brought up a good point. I don't know enough about how that works to say if you're in good shape after the dealership reset or not. But the other thing to check is whether the steering wheel was actually removed from the steering shaft and "reclocked" differently on the splines to make up for an off-center steering wheel. I've seen this done before by shops that don't know what they're doing. It screws up steering geometry because it leaves you with steering links of different lengths on each side. It's the wrong way to deal with an off-center steering wheel, and I could imagine it also confusing the SAS. A long time ago I had a dealership do this on a Passat I owned. The proper way to adjust steering wheel angle is with the threaded tie rods. If those don't get the job done, then you have a bigger issue with the rear not tracking correctly with the front. However, I think that would throw your thrust angle off, and yours is perfect, so don't think that's the issue.