Originally posted by Rich Browne
Scrub Radius. This is distance from the center of the tire to the point where a line down the kingpin axis intersects the ground. Along with caster this affects wheel lift during cornering. Scrub radius is set using spacers on the stub axle. It has an effect on turn in and push on power.
Thanks Rich, I think I get it now. The "scrub set" is changed by moving the spacers around inside and outside the knuckles/hubs.