1975 NASCAR International Stock Car Racing Rule Book NASCAR Grand National ® Championship Division Section 20-16 -- Suspensions

a. Heavy duty springs may be used if similar to original equipment. Rear spring position may be changed, but both springs must be located either inside or outside of frame rails. When using a car that has original rear coil spring suspension it is permissible to use pickup truck trailing arms. Absolutely no tubular trailing arms or trailing arms using heim joints. Standard type rubber or metal bushings must be used. No lead to be added to lower trailing arms.

b. Sway bars may be reinforced. Additional sway bars permitted. Sway bars may use NASCAR approved heim joints as connecting linkage.

c. Front end suspensions must be reinforced for safety. Heavy duty spindles and bearings compulsory. Absolutely no heim joints permitted on steering linkage or upper and lower A Frames. Adjustable A Frames not allowed.

d. Camber: 4° maximum.

e. Wheelbase: AMA specs apply. Standard plus or minus 1/2 inch. Both front A-frames may be moved forward not more than 1 inch from original position. Left and right must agree. Wheelbase must remain the same as manufactured, as referenced by measurements from front door jamb post to front axle or overall length of car. In case of eligible cars having less than 115" wheelbase, rear axle assembly must be moved towards rear of frame to conform to minimum 115" wheelbase. When measuring wheelbase, one side measurement must be the minimum allowable wheelbase for the model. Maximum allowable tolerance can not exceed 1/2 inch plus or minus on the other side.

f. Tread, front and rear: AMA specs apply plus or minus not over 1 1/2 inch tolerance on either side to allow for reinforcement of wheels and hubs, measured at center of tire, zero toe-in at spindle height. Steel spacers are permitted to utilize maximum allowable tread width. Spacers must be bolted or welded to brake drum or hub. "A" frames must have a stock appearance. Upper and lower "A" frames may be altered for safety and tire clearance. Lower "A" frames must be the same length and mount in the stock position. Left and right must agree. No offsets permitted.

g. No mechanical or hydraulic device for shifting weight will be permitted inside of driver compartment. No hydraulic weight shifting devices permitted at any time. No weight lowering adjustment permitted on left front wheel during a race.

h. BODY HEIGHT AND GROUND CLEARANCE MEASUREMENT PROCEDURE

Car height off ground and body height, including rake or degrees of body angle, shall be determined by measuring overall height of car from a distance of 10 inches behind the top of the windshield on the roof center line. Maximum body angle shall be two (2) degrees measured along the roof center line.