Here's a paragraph out of the NSRA Vehicle-Safety-Inspection Requirements...Joe
Scrub Line...........
Dual master cylinder recommended. On both the front and rear suspension of the vehicle, stretch a taut string from the bottom of each wheel rim to the bottom of each of the other three tires at the road surface. If any part of the steering, suspension, or chassis is below this string, the vehicle will fail scrub line test. Allow an additional 1/4-in. assuming the tire will not come off the rim if the tire should go flat. Items exempt from scrub line check will include body sheet metal, bumpers, exhaust system, oil and transmission pan.
