Square Wheels,

I had very little time to do this, but I searched on scrub radius as you did and found this under toe on the familycar.com/alignment site:

"In the early days prior to radial tires, extra toe-in was added to compensate for tire drag at highway speed."

I realize that this could sound out of context, so here is the entire paragraph:

"Like camber, toe will change depending on vehicle speed. As aerodynamic forces change the riding height, the toe setting may change due to the geometry of the steering linkage in relation to the geometry of the suspension. Because of this, specifications are determined for a vehicle that is not moving based on the toe being at zero when the vehicle is at highway speed. In the early days prior to radial tires, extra toe-in was added to compensate for tire drag at highway speed."

I hope to find more time to explore this further. As you said, there is lots of information out there and if one is not careful, they might mess around and learn something. So, I hope to learn something from this search when I get just a little more time.

Have a great day,
Doc

 

I read the postings rather quickly,did anyone mention a wheel with run out. Scribing a line or useing thumb tacks takes care of that problem since your measuring from the
same point. I never used the tread grooves. You can also use string, that takes a bit more time, now that these inexpensive lasers for the building trades are around I'm
sure you could project a line parallel to the track of the rear axle and make you measurements off of it. Kind of like we did with string only easier once you make the
rigging.

 

Yes, accounting for tire lateral runout has been thoroughly discussed. And you are correct, now that lasers are very inexpensive, a fixture could be made that could clamp to the wheel with a reflector and a target for the home mechanic. It could be made pretty cheaply nowdays I expect.

Have a great day,
Doc