I'm not sure what the Longacre tool you have works like but I use a Caster/Camber tool that I bought in the 80's for Formula Ford Race Car set up. It's a very simple piece in design but can result in some very accurate settings.
I use the "string" method along with this tool to square up the front and rear and to be sure the front wheels ends up in line with the rear. It is tedious to do but again, the results are very accurate.
Basicly I start by putting the car on a perfectly flat area with all the tire pressures set to spec. I then put support strands to tie the string to all around the perimeter of the car. I use 4 jack stands to attach the string to and can move these stands freely around that way, but you can use any sutible stable device for this. I square the string up with the rear wheels about an inch from them on each side. I use a Dial Caliper to set the string equal distances from the rim edge to the string.
From that I can now square up the front and set the Toe measuring from the string to the wheel edge using my Dial Caliper. If you want the results in degrees you have to use your Geometry skills to calculate that out.
Once the Toe is set I set the Camber using my Caster/Camber tool and go back and recheck the Toe making sure that didn't change. If the Camber was changed it will move the Toe setting so that is why you should recheck it.
I then take a large square, place it against the outside front and rear edge of the front tire and mark a line on the floor at the edge of the square where it touches the floor. Then I use a straight edge and draw a line from those 2 points on the floor.
Using that line as a reference I turn the front wheels 30 degrees in each direction and measure the Camber at each of those positions. Then I use the formula that came with my Caster/Camber tool and calculate the Caster setting from that.
All and all it takes me awhile to do but one thing for sure I know what I came out with, not what somebody says they did, and I am satisfied that my car was taken care of while this job was done.
