Ok here goes nuthin'
You get the secondary side of the gauges to start off with. There are a series of slots on each upward casting. You select the slot that is the nearest in height to the centre of the wheel height.
Slots in casting:
Gauge bar in slot that most closely approximates hub height (It's a toss up between this slot and the next one up, but this one is close enough)
You then set all the guage bars at that height and adjust them so they touch the wheel, tyre or wherever you want to take the measurement.
I used the edge of the rim, because the trim rings stopped me using the side of the rim
You then bring the two sides of the gauges together and set up the gauge bars on the other side to match the first side.
With the two sides of the gauge touching together you set the optical scale to zero. This is very difficult to photograph, but easier when you look down therough the little spyhole.
You move the pointer to align the vertical line with the triangular pointer whick is reflected back by the mirror.
The gauges feature an old fashioned dial calculator. You set the dial to match the diameter of the wheel.
You then use the other side of the dial to convert the desired toe in into degrees and minutes which the gauge uses.
So if you want 1/8" toe in, you want just over 15 minutes.
The gauges are now calibrated to each other at a zero setting. So make sure the pointer points to zero on the scale. Move the scale to align with the pointer if necessary. This is a home made pointer, the proper job part features a magnifying lens.
Then you take the gauges to the car and position them against the wheels. The car should be rolled forwards into position.
You then sight down the eyepiece and move the pointer until the triangle aligns with the line. (Even more difficult to photograph as the image is further away due to the distance between the gauges.)
Now for the moment of truth: Read out the alignment in minutes from the gauge plate.
Now here's the moment of truth. Ok, it's miles out. I'm reading 50 minutes, which if you read it back through the calculator that' over 3/8" toe in. I should be shooting for about 15 minutes or just above which equates to 1/8" or so.
Time to get out and get under and make an adjustment!
(Actually I muffed the reading I shuffled the steering as the wheels were not straight. That nullifies the test. I should have rolled the car out and back in again with the wheels straight.)
I used them for real last night and once the initial setup is done they are quick and easy and accurate to use.
Mart.