13.5 SHOCK ABSORBERS/STRUTS
A. The make of shock absorbers, struts, and strut housings may be substituted providing that the number, type (e.g., tube, lever, etc.), system of attachment and attachment points are not altered, except as noted below. The interchange of gas and hydraulic shocks absorbers is permitted. The following restrictions apply:
1. No more than 2 (two) separate external shock damping adjustment controls are allowed. This permits the use of shocks which originally came with more than two external adjustments, which have been converted to double-adjustables, only if the additional adjustment controls have been permanently disabled (e.g., via welding, epoxying, grinding off). Gas pressure adjustment is not considered a damping adjustment.
2. Suspension geometry and alignment capability, not including ride height, may not be altered by the substitution of alternate shock absorbers. Aftermarket strut housings are allowed provided that they meet the Street category shock requirements defined herein (i.e., that no suspension geometry changes result). This includes the position of the steering arm attachment point in the case of struts with integrated steering arms.
3. Adjustable spring perches are allowed, but the spring loadbearing surface must be in the same location relative to the hub as on the standard part. Shims may be used to achieve compliance.
4. The fully extended length must be within ±1" (±25.4 mm) of the dimension of the standard part.
5. Electronically controlled shocks may not be used on vehicles that did not have an option for them from the manufacturer. A full option package upgrade, including OE electronics and other comonents, could be completed to add electronic shocks if they were not installed from the manufacturer.
6. Vehicles equipped with electronic shocks can replace them with nonelectronically-controlled shocks subject to Sections 13.5 and 13.9. Devices may be added to satisfy the ECU that the OEM shocks are still installed; such devices may perform no other function.
7. On cars with available electronically-controlled shocks, aftermarket electronic shocks may be substituted but may only be controlled by an OE shock control unit and may not contain independent or additional control logic within the shock itself. No additional electronic modifications can be made to facilitate the installation of aftermarket electronic shocks, and the OE controller may not be modified or reprogrammed.
8. Vehicles originally equipped with an adaptive ride control system (MSRC, MRC, PASM, AMS, etc.) may alter the calibration using an OEM-provided re-flash or the entire controller may be replaced. The calibration or replacement controller may not perform any function not present in the OE controller. OEM shock/strut bodies and internals must remain unaltered. Additional sensors are not allowed. No modifications to the wiring harness are allowed.
B. The mounting hardware shall be of the original type. The use of any shock absorber bushing material, including metal, is permitted. Pressed or bonded bushings may be removed from standard parts to facilitate the use of alternate bushings which fit in the original location without alterations to the part. This does not permit the use of an offset shock bushing. A shock absorber bushing may be implemented as a spherical bearing. The bushing attaching the end of a strut to the body or frame on a strut type suspension is a suspension bushing, not a shock bushing. For cars with a bayonet/shaft-type upper shock mount, this allowance permits the removal of the shock bushing from the upper mounting plate (e.g., drilling, cutting, burning out the bushing) and replacing it with another bushing. This also includes shock bushings located in control arms, etc. This does not allow other modifications to the plate itself or use of an alternate plate.
C. To facilitate the installation of commonly available aftermarket shock absorbers, struts, or strut inserts whose shaft size is larger than the center hole of an upper shock mount assembly, that hole may be enlarged by the minimum necessary to accommodate the shock shaft size, provided the following restrictions are met:
1. The enlarged hole must remain concentric with the original configuration.
2. The enlargement of the hole does not require modification of a bearing (as opposed to a washer, sleeve, or plate).
3. Neither the hole enlargement nor the location of the shock shaft changes any alignment parameter. Provided these constraints are met, this permits enlarging of the center hole in an upper shock mount with an integrated rubber bushing, where the bushing is integral to the mount and bonded to the plate and the mount is provided by the OEM as an assembly. This includes drilling out and/or removal of the metal sleeve.
D. A suspension bump stop is considered to be performing the function of a spring. Therefore, the compressed length of the shock at the initial point of contact with the bump stop may not be increased from the standard part, although the bump stop may be shortened. Bump stops installed externally and concentric with the shaft of a shock may be drilled out to fit a larger diameter shock shaft. Bump stops may be substituted provided they meet the length requirements and are in the same location as stock.
E. A hole may be added through the bodywork to route the reservoir and hose to a remote mounting location. Such holes may serve no other purpose.
F. A hole may be added to interior body panels, the engine compartment, the trunk, and/or a strut bar to provide access to the adjustment mechanism on a shock absorber. The hole may serve no other purpose and may not be added through the exterior body panels.