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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
So brought the car to get a full alignment I was told they couldn't straighten the rear even by adjusting the panhard bar it would get to the point that the drive shaft would bind if he went any further. Here is a picture of the results. I did just rebuild the rear end but I can't imagine anything I did would cause this, what's the general consensus. could something just be bent? As for alignment those numbers mean nothing to me but the guy told me that was pretty far off .any thoughts?
When I was at Hunter, I got to see a lot of alignment printouts for the vehicles we tested. It was usually normal to see a small negative camber value on the rears of a solid axle vehicle. Not much, but it was a nonzero amount. I think this is a screenshot before I tweaked the alignment on my 85. You can see a minimal amount of camber on the rear, but it is basically nonexistent. .03 is what I would expect, but your .3 and .5 are pretty excessive. Seems like the rear end is bent at those values. My other guesses are: Shop didn't do the rolling comp correctly, which skewed alignment values, bearing races are minused on your axles so they aren't parallel to horizontal anymore, axle tubes got bent. Runout on the hub is taken into account during the alignment process, so a bent flange at the wheel hub shouldn't change alignment values.
No amount of suspension adjusting will remove a 1/2 degree of camber from each side on a solid axle. Adjustable control arms will let you dial in the thrust angle of the rear end and that's about it.
When I was at Hunter, I got to see a lot of alignment printouts for the vehicles we tested. It was usually normal to see a small negative camber value on the rears of a solid axle vehicle. Not much, but it was a nonzero amount. I think this is a screenshot before I tweaked the alignment on my 85. You can see a minimal amount of camber on the rear, but it is basically nonexistent. .03 is what I would expect, but your .3 and .5 are pretty excessive. Seems like the rear end is bent at those values. My other guesses are: Shop didn't do the rolling comp correctly, which skewed alignment values, bearing races are minused on your axles so they aren't parallel to horizontal anymore, axle tubes got bent. Runout on the hub is taken into account during the alignment process, so a bent flange at the wheel hub shouldn't change alignment values.
No amount of suspension adjusting will remove a 1/2 degree of camber from each side on a solid axle. Adjustable control arms will let you dial in the thrust angle of the rear end and that's about it.
did you intend to have your driver vs passenger camber that different on the front?
No. I mentioned that screenshot was before I actually aligned anything. I'm not sure what I settled on back then. This was around 5+ years ago. I slapped on some new strut mounts the day before I took this photo, so that is why the camber was off by a good margin. I measured best I could to put them where the old mounts were, measuring off hard points on the body to the tip of the strut. Close enough for what I needed at the time.
Currently, I run -1.5 degrees on each side, zero toe, and 4.5 degrees of caster. No point in having any cross camber or caster for what I do with the car.
No. I mentioned that screenshot was before I actually aligned anything. I'm not sure what I settled on back then. This was around 5+ years ago. I slapped on some new strut mounts the day before I took this photo, so that is why the camber was off by a good margin. I measured best I could to put them where the old mounts were, measuring off hard points on the body to the tip of the strut. Close enough for what I needed at the time.
Currently, I run -1.5 degrees on each side, zero toe, and 4.5 degrees of caster. No point in having any cross camber or caster for what I do with the car.
thanks, sounds great... also just for reference is the SAI value you show in the screenshot typical of what you would in the end expect... seems like it is from things i have found informally, but this is a number i have been having a hard time finding the true actual optimal value for our set-ups
Looks to me like either the rear housing or the CAs are bent.
I believe he meant that the amount of adjustment he had to make to correct the alignment was putting stress on the drive shaft that's what I understood from the shop
thanks, sounds great... also just for reference is the SAI value you show in the screenshot typical of what you would in the end expect... seems like it is from things i have found informally, but this is a number i have been having a hard time finding the true actual optimal value for our set-ups
Nothing is modified on my spindles or struts to alter SAI beyond factory allowances, although the strut mount point is moved 1" upwards with the aftermarket caster/camber plates. The cross between them is probably from me not paying attention when I torqued the struts to the spindle. I might have had the spindle pulled up on one side but not the other. I can't say I've worried about it too much. There are many other threads here about opening up the mount holes to allow SAI to be adjusted more.
I would expect my SAI numbers to be pretty typical, seems close enough to the original values from the OP.
When I was at Hunter, I got to see a lot of alignment printouts for the vehicles we tested. It was usually normal to see a small negative camber value on the rears of a solid axle vehicle. Not much, but it was a nonzero amount. I think this is a screenshot before I tweaked the alignment on my 85. You can see a minimal amount of camber on the rear, but it is basically nonexistent. .03 is what I would expect, but your .3 and .5 are pretty excessive. Seems like the rear end is bent at those values. My other guesses are: Shop didn't do the rolling comp correctly, which skewed alignment values, bearing races are minused on your axles so they aren't parallel to horizontal anymore, axle tubes got bent. Runout on the hub is taken into account during the alignment process, so a bent flange at the wheel hub shouldn't change alignment values.
No amount of suspension adjusting will remove a 1/2 degree of camber from each side on a solid axle. Adjustable control arms will let you dial in the thrust angle of the rear end and that's about it.
are axle tubes getting bent a common thing? Forgive my ignorance on this matter
.03° is basically ZERO in an automotive application. I don't think I've ever even seen alignment specs carried out to more than 1 decimal place in the degree specs; and even then, you can bump or jiggle a car on the rack, and the measurements often will settle back down to more than .1° from where they were before, anyway. I can't feature how a vehicle with rubber bushings and a sheet-metal unibody could EVER be precise enough to warrant alignment measurements in thousandths of a degree. Measure with micrometer, mark with chalk, cut with axe.
Axle tubes don't so much "bend", as become loose in the pumpkin. They're steel but the pumpkin is cast-iron. The factory jams the tubes into the pumpkin and then uses those little plug welds that are about 3/8" dia, 2 on each side, to hold them in place. Those welds always crack, and when that happens the tubes can wobble around all over the place, and usually the welds themselves leeeeeek besides. That's where any camber or toe comes from: camber is from when the tubes move up or down from their correct position, and toe when they move front or rearwards; or, if they weren't located accurately when the welds were welded. Solid axle rears don't really have caster since they don't steer.
No, changing axle seals won't affect alignment, at least not in the first couple of decimal places.
putting stress on the drive shaft
That makes no sense whatsoever. Sounds like he was pumping your rectum full of sunshine for some reason. For one thing, if you have a stock Panhard bar, it isn't adjustable, anyway; you bolt it on, and whatever it is, is what it is. The axle's centering changes as the rear articulates though.
Thrust angle means that the rear is not pointed straight behind the front. Makes the car "crab" or "walk sideways". It comes from the wheelbase not being the same length on both sides, although that can be caused by front alignment sometimes too, since some front adjustments also move the front wheels front or rearwards. But if you measure from one of the fixed points on the chassis, from say the front control arm mounts or one of the factory index holes on each side, to the axle end of the 2 rear control arms, that length should be the same, within a few tenths of an inch.
Note that the factory tolerance is 3mm, which is about 1/8". We can do better than that if we try but that gives a good idea as to how many decimal places are appropriate.
.03° is basically ZERO in an automotive application. I don't think I've ever even seen alignment specs carried out to more than 1 decimal place in the degree specs; and even then, you can bump or jiggle a car on the rack, and the measurements often will settle back down to more than .1° from where they were before, anyway. I can't feature how a vehicle with rubber bushings and a sheet-metal unibody could EVER be precise enough to warrant alignment measurements in thousandths of a degree. Measure with micrometer, mark with chalk, cut with axe.
Axle tubes don't so much "bend", as become loose in the pumpkin. They're steel but the pumpkin is cast-iron. The factory jams the tubes into the pumpkin and then uses those little plug welds that are about 3/8" dia, 2 on each side, to hold them in place. Those welds always crack, and when that happens the tubes can wobble around all over the place, and usually the welds themselves leeeeeek besides. That's where any camber or toe comes from: camber is from when the tubes move up or down from their correct position, and toe when they move front or rearwards; or, if they weren't located accurately when the welds were welded. Solid axle rears don't really have caster since they don't steer.
No, changing axle seals won't affect alignment, at least not in the first couple of decimal places.
That makes no sense whatsoever. Sounds like he was pumping your rectum full of sunshine for some reason. For one thing, if you have a stock Panhard bar, it isn't adjustable, anyway; you bolt it on, and whatever it is, is what it is. The axle's centering changes as the rear articulates though.
Thrust angle means that the rear is not pointed straight behind the front. Makes the car "crab" or "walk sideways". It comes from the wheelbase not being the same length on both sides, although that can be caused by front alignment sometimes too, since some front adjustments also move the front wheels front or rearwards. But if you measure from one of the fixed points on the chassis, from say the front control arm mounts or one of the factory index holes on each side, to the axle end of the 2 rear control arms, that length should be the same, within a few tenths of an inch.
Thank you for the information. Just wanted to make sure that there was nothing I could have done doing removal and installation of the rear to cause this. I'm going to read your information again a couple of times to get this brain to get a better understanding🤪
01-01-2024, 11:33 PM
Adjustable control arms will let you dial in the thrust angle of the rear end and that's about it.
