1961 NASCAR International Rule Book Specifications NASCAR Grand National Championship Circuit Section 21-29 -- Tires

a. No knobs, powergrip baldies, speedway treads, or worn out tires allowed. No cross grooving allowed. Standard treads only. Racing rubber permitted. For tire sizes on all models consult allowable sizes on specifications chart. For speed trials and record attempts, tire size must be standard and approved by NASCAR officials.

All four tires must be the same size as to actual measurement.

b. Experimental tires are not eligible unless approved by NASCAR.

c. Recaps must be approved by NASCAR, and recaps will not be permitted on any track one mile or over in size.