A. Rear suspension configuration used on current and new chassis(s) must be the design commonly known as four (4) link. Older cars currently competing with other rear suspension designs will be allowed to compete until further notification at the discretion of the Series Director.
B. The frame/roll cage structure must have integral welded mounting brackets for the attachment of rear suspension components. Frame suspension mounts may be welded or bolted securely (without any movement) to the frame/roll cage structure.
C. The only material used to fabricate frame suspension mounts that will be permitted is magnetic steel.
D. Axle Housing Mounts:
a. Aluminum birdcages will not be permitted.
b. Axle housing mounts may be a solid (welded) type or a floating type (birdcage) design.
c. Only one (1) axle housing mount per side will be permitted.
E. The final assembled axle housing mount must be a one (1) piece mount. When a floating type mount (birdcage) is fabricated using two (2) pieces, the two (2) pieces must create a common one (1) piece pivot (barrel). The two (2) pieces must be fastened or welded together to prevent independent movement of the two (2) pieces. The axle housing mount must attach directly to the axle tube with clearance only to permit rotation of the entire mount. Fore, aft or vertical movement of the mount or the axle housing within the mount will not be permitted.
F. Only 2 (two) radius rods per side will be permitted to be connected from the axle housing mounts (birdcages) to the frame. Radius rods must be magnetic steel. Spring rods or any type of radius rods that change length dynamically are not permitted. (See Brakes 22.7.6D for floating caliper specifications)
G. Radius rods must attach to the frame brackets and to the birdcages using metal spherical rod ends or mono ball type bearings. Non- metallic bearings and or bushings will not be permitted. All mounting holes for attaching radius rods must be round and properly fit the fastener being used to prevent movement.
H. Independent rear suspensions will not be permitted.
I. In regard to swing arm and/or Z-Link suspension, these suspension types are permitted. The shock on a swing arm or z-link rear suspension may mount to the bird cage or bottom radius rod. Top and bottom solid links must be mounted on hiems and run in the opposite direction of bird cage.