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Originally Posted by mbtoloczko
Did you jack the wheel off the ground to get the measurement?
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Heh. Sort of.
I placed a floor jack under each ball joint and lifted until the tires were lightly touching the ground. This kept the car from shifting side to side while performing my test. I turned the steering wheel side to side several times and then jacked the car up until I could rotate the wheels. I turned the front wheels 180 degrees to prevent any 'contamination' to the rub marks I'd just made on the tread. After removing the tires it was very apparent from the markings, the spot on the tread which they pivoted about. I measured the width of the tires (sidewall to sidewall, 244.5mm) and divided by two (122.25mm.) From the center of the tread, I measured the distance to the center of the pivot markings (27.0mm.) I did this to both tires and arrived at the same answer plus or minus one millimeter. My tires are basically slicks right now, which made finding the exact center of the pivot markings very easy.
I'm tempted to remove a wheel and attach a straight-edge to the hub flange so that it nearly touches the ground. The end of the straight-edge should draw an arc on the ground when turning the wheel. From there, the radius of the arc would be added to or subtracted from, (depending on whether the arc is convex or concave in relative perspective, to) the offset of the wheel. The resultant number should be the scrub radius. It's important with this method that the hub be the normal operating distance from the ground or the radius of the arc will change.
I suspect the resultant answer using this technique would be very close to the result of my first test. For my purposes, I'm happy if I'm within a centimeter, but I suspect I'm much closer than that. Nevertheless, I'd like to do another test using a different method just to validate the first test.
I welcome more input -
unless it disagrees with me, of course. 