1968 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Circuit Section 20-27 -- Tires

a. No knobs, powergrip baldies, slicks or drag tires permitted. No cross grooving allowed. Standard treads only. Racing rubber permitted.

b. All four tires must be the same size as to actual measurement, and must be of the same make and the same tread design.

c. A measuring device (shown in diagram on rear pages of Rule Book) will be used to determine maximum size of tire. To obtain accurate reading, inflate tire to 60 pounds, place measuring device over tire and exert slight hand pressure.

d. Recaps must be approved by organizer, and recaps will not be permitted on any track one mile or over in size. Width of any recap tread cannot exceed width of original new tread for that tire and the maximum retread width is 10 inches. When retread tires are used, all four tires must be the same width and tread design.

e. Same type tread and grade rubber must be available to all contestants. Any deviation from this rule must be approved by the NASCAR Technical Director.

f. Stock racing tires, with inner safety tires, compulsory on all NASCAR super-speedways and other specified tracks. Violation of this rule will result in fine and/or disqualification of the car.