This will be a little bit complicated, because I don't have one handy to make pictures, and I can't find a pic online.
You can only approximate the location by measuring it, final adjustment needs to be made by measuring the wheel's caster, but you can get it close enough by measuring the old location, assuming that it wasn't bent. You need to find the location of the inner locknut on the original, and just use that as your starting point to get it to the alignment shop. If you didn't move the nut, just install it as is. If you are planning to remove the nut for cleaning/painting, you need to measure from the edge of the nut to the center of the mounting hole, write that down and retighten it to the same position after painting. If you have already painted it, you can probably see still where the clean part of the threads are, which will indicate the original location of the nut.
When you take it to get aligned, you need to make sure that the shop is even interested in adjusting the caster first. Having worked briefly in a tire shop in my younger days, I can tell you that most places don't do caster because modern cars have no adjustment, and frankly mechanics don't want to mess with it. It's usually adjusted only when you complain after getting a bad alignment. You will have to make sure you say specifically that you're there for caster adjustment, and check the printout they give you to make sure they bothered adjusting it.
When it comes time to have the caster adjusted, since you have the book, you have the original specs. The original caster spec is good for bias ply tires, but no good for radials. Bias ply tires are flexible, and go egg shaped at higher speed, which gives an extra degree of positive caster, because the point of road contact is one degree or so behind the centerline of the spindle. Radial tires stay round until much higher speeds, so the caster will need to be adjusted +1 degree positive for radial tires. You should take the shop manual specs with you to compare the specs they give on the printout with the specs in the book, if you're running radials, have them add one to the caster in the book, but if you're running Coker bias or similar, use the original data.
Thanks for taking the time to help answer my question! Good point on radial tires which I do run. So your saying that their a alignment machine that is needed to set the caster? You cannot set the caster at home with a bubble level? Thanks Dave
you could possibly do a decent home alignment, not perfect, but good enough.
There is a tool available to do rough caster/camber at home, I have one, and it works well, but it attaches to the wheel hub magnetically and doesn't factor out runout or surface damage on the hub. for some reason, when I try pasting an image of it, it covers the text, no matter how I change the html, so google caster camber adjustment tool and you'll see it.
the one I have:
The problem you will have doing it with a level are manifold:
number one, the place you put the level must be chosen to negate runout. I mean to say that you will need to the rim to rest the level on, but the rim can vary from true by enough to throw off your measurements by degrees. So you will need to clean the rim and use a dial indicator to find the points of highest and lowest axial runout, and then put those points at the 3 o clock and 9 o'clock position, so the closest to average parts of the rim are in the vertical line where camber is measured. You cannot use the tire to rest the level against, because the measurements must be taken on the ground with the suspension at ride height, and the weight will bulge the bottom of the tire, making it useless as a reference. Make sure the level doesn't touch the tire, that all measurements are taken on the rim or from a jig mounted to the spindle.
number two, levels are not graduated for degrees. Carpenter levels are not graduated at all, and machinist levels are graduated in thousands of inches or in tenths millimeters horizontally. So you would have to do some math, basic trigonometry. You will need to measure exactly the distance between the points of contact between the level and the rim and then figure out exactly how far that point is away from level. You will need to divide the distance away from plumb by the distance between the points of contact, and this will give you the sine for the camber angle, in radians. You will then need to find out what angle that corresponds with in degrees, either online, or if you have a machinist's book or trig textbook, you can use the charts there. The corresponding number is the camber for where the wheel is sitting. To find the caster, you need to turn the wheel twenty degrees to the right from straight ahead, measure the camber, turn it back twenty degrees to the left from straight ahead, remeasure, and then subtract the second camber from the first. This sounds much harder than it actually is, and it can be done, but it will only be as accurate as the level you're using and the corrections you make for the floor the car sits on. If you have a machinists level and a dial indicator, you can probably do a better alignment than a shop, who may never bother calibrating their machines, but if you have a carpenter's level, you'd just be coming close enough.
I do all my own alignments with this set available on Amazon and Summit Racing for $209, works great.
Dave, don't buy the cheap stuff the other guys suggest. Go pro.
I agree, technically I didn't suggest anything, but if I did, i'd suggest using Anders' credit card and going nutzo. LOL
My actual suggestion is going to a shop, finding a guy over 30 to work on the car, tipping him to do it right, and buying a lifetime alignment. Then you can take it back every year if you like, since you're keeping the car.
But, if you're the type who absolutely needs to do it yourself, I like to give tips on how to do it, why not to do it, and how it can go wrong. Please don't take them as suggestions, some of the people on this site have a problem with being the last word on things, i'm not doing that, just illuminating the process for people who find it interesting.
My post was intended as a joke. Nothing else. My CC is maxed out. Bought four new nice tires (white wall ofc) for the Buick Estate Wagon today. It made an even bigger hole in the CC!
Mark, I truly enjoy reading your recommendations, explanations and suggestions. Thanks for taking your time writing.