Re: Tire sizes and steering
pdq67~ if I am reading your post correctly, you are close.
Two imaginary lines define scrub radius. One is the vertical line through the tire center line to the plane of the ground. The other one is the line through the pivot points of the upper and lower BJ to the same ground plane. The most common term for that line is called the kingpin inclenation angle. The distance between the two points on the ground plane is scrub radius. The tire wants to rotate around its center while the car rotates it around the kingpin inclenation. As you can see the more distance between those two points, more scrub radius, the more friction the tire generates so more force is needed to turn the tires. I hope this helps.