This kit is a simple chop & weld coilover adapter, with included roll-center adjusters. The combination of these two products allows extra camber adjustment and increased wheel backspace, but with some creativity, there’s a host of crazy geometries available by rotating a camber plate at the top of the coilover to become a caster plate, or extending the lower control arm.
In the 240SX world, people pay a lot of money for “drop spindles” to accomplish what this kit does. On a 240SX, the steering knuckle and coilover mount are all cast in once piece, so there is no way to change either roll-center, or strut mounting height. The RCA kit included gives you the equivalent of a 25-30mm RC corrected “drop spindle” depending on how the parts are setup and aligned. With the further advantage of allowing significant camber adjustment, well beyond what any of those aftermarket spindles can offer.
The installation of the kit changes the camber/caster curves from the factory specs, it separates the strut axis and steering axis, just like the 240sx or any other vehicle using a similar style offset bracket, this has advantages and potential disadvantages. One such benefit of a adjusting camber at the wheel is freedom to install the camber plate at the top of the strut rotated to be a caster plate.
The roll-center adjusters push the spindle+hub outboard about 12-13mm relative to the balljoint, and the coilover adapters move the strut inboard significantly, but the distance to the upper lip of the wheel will vary by camber setting. Therefore, the use of more commonly available higher offset wheels is possible, or wider wheels at the same offset, while maintaining the same strut-to-wheel clearance and scrub radius.
The inclusion of roll-center correction is also important. The majority of coilovers in this application will be short, they will force the car to sit significantly lower than factory ride height, as such, there will be a greater tendency for body roll. While stiffer springs and stiffer anti-roll bars will reduce the effect, they reduce or limit body roll only once it begins, they do not help prevent body roll. A proper roll-center adjuster changes the willingness of the car’s body to roll, by changing how cornering forces act on the suspension, allowing a much higher cornering and transition speed.
For anyone participating in drifting, the increased wheel clearance, the option of minimizing caster, along with the ability to flatten the leading wheel to the ground will be a boon. For road racing or time attack, the ability to use high-quality digressive coilovers that are unavailable for the integrated Macpherson strut, and potentially the track width increase, will be the greatest benefit. And for an ordinary street application, it will allow the use of inexpensive used 240SX coilovers to begin with, but allowing a clear upgrade path to better parts, or towards a more race oriented setup later.
Welding is required, specifically the body to where the strut tube is cut off, the assembled pictures only show unwelded parts. In some cases the remaining strut tube will be out-of-round or possibly even bent, some light dremel work to improve the adapter fitment may be required, or alternately, the adapter might have to be pressed in with hydraulic press. There is a retaining screw that can secure the adapter from underneath for welding, provided a 12mm or 1/2″ hole is drilled in the bottom of the tube.
Because this is an advanced handling kit designed to allow a wide range of adjustment, there is no ideal setting, products used, and ultimately the goals for the car will determine the correct approach. It is recommended to consult with an alignment shop familiar with race car setup if deviating from factory settings; discuss the intended use, they should be able to recommend base settings, and then adjust accordingly.
The use of S13-specific coilovers is actually more of a recommendation, S14-specific front coilovers are also possible to use with the reducing washer kit available in the S13 section on the left. They are inserted into the S14 coilover bracket bolt holes which normally use 14mm bolts, and reduces the bores to 12mm like the adapters require.