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(Rushed to print)
Art,
I know just what you mean, but here's how I use it (best with a helper). Keep in mind that I've added an inward pointing tip to outer end of the swinging "needle", and a matching one at the other end of the gauge, for a touch of shadetree precision. Also keep in mind you can almost do the measurement in less time than it takes to read the following and (hopefully) make sense of it—
1 - Slide the gauge behind the tires, then set each end up on three 2" x 4" blocks placed behind the tires. Next, angle the ends up about 45° to touch the fattest part of the tire bulge. This will be a little below hub centerline height. You'll need a helper on the right side to hold the gauge up in this angular position on the Right tire.
2 - Eyeball each side to see that the measuring tips are in the same relative position, then "zero" the gauge pointer (on the Left side) and lock the sliding part.
3 - Now move the gauge and wood blocks around to the front of the wheels, where your helper positions and holds the tip angled up to the tire bulge at the front of the Left tire—again close to hub height.
4 - At this point I sorta wing it—I don't use the gauge markings at all—I set the pointer to 0 (the rear measurement) and hold it there while I position the "needle" pointer up toward the Right tire bulge. With any Toe-in at all, the pointer won't touch the tire. I eyeball this space, and sometimes "measure" it with something like a 2mm allen wrench as a go/no-go test if it looks really wide.
Referring to Bentley pages 620-1&2, we are measuring very close to where the spec is 2.0mm ±1.0mm (see B-to-b), except we are measuring on the outside of the tire bulge rather than inside.
In my opinion, the main thing is to have some observable Toe-in. I try for no more than 1.0mm using this admittedly crude method. If the car feels twitchy on a test drive, and seems to need a lot of attention, I recheck and may increase the Toe-in closer to 2.0mm.
Note that 2.0mm is my max (rather than Bentley's 3.0mm) because I can't quite reach up to measure at the hub centerline, and am thus comparing two measurements that are slightly "below spec" because the horizontal distance between my rear and front measuring points is less (tending toward C-to-c).
Actually making the Toe adjustment is maybe best covered separately. But IMO, IARS (It Aint.....).
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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