AFCOs Dual Stage Coil-Over assembly provides variable spring rates that can be used to improve traction and handling in the slickest of conditions. Additionally, the assemblies can help eliminate suspension bottoming problems common with todays dirt late model racecars.
SOME POPULAR SET-UPS*
Left Rear: You can use Afcos Dual Stage Coil-Over assembly on the left rear to help improve forward bite off the corners in the slickest of conditions. Start out with a 200 #/inch primary and a 400 #/inch secondary spring. The primary springs should be at least 12 inches tall and the secondary springs should be at least 4 inches tall to avoid potential coil-bind problems on left rear suspension applications. Set ride heights with the dual jam nuts not contacting the slider assembly. Adjust the jam nuts to just touch the slider assembly after ride heights have been set. This set-up provides a relatively soft, 133 #/inch spring rate during rebound travel beyond ride height, which lets a chassis hike up easily and develop left rear drive off the corners. However, this set-up produces a stiffened compression rate of 200 #/inch during compression travel beyond ride height. This staged rise in spring rate increases weight transfer to the left rear tire during initial acceleration, which helps to improve forward bite. Also, the soft initial spring rate of this dual spring assembly requires additional preloading of the coil-over assembly in order to maintain left rear ride heights. The extra preload helps to keep the coil-over assembly loaded at all times, which can improve overall traction and handling consistency.
Right Rear: Start with a 400 #/inch primary and a 300 #/inch secondary spring to free overall handling in heavy track conditions. Set ride heights with the dual jam nuts not contacting the slider assembly. Adjust the jam nuts to achieve a 2 inch gap (to start) between the jam nuts and slider assembly after ride heights have been set. This set-up provides a 171 #/inch rate at corner entry and a 400 #/inch rate at corner exit. Use 8 inch tall springs to avoid potential coil bind problems.
Right Front: Start out with Afcos specially designed 26400-3 secondary and 26700-2 primary springs on your right front coil-over. These springs are specially designed to eliminate coil-bind and the need to compress the spring assembly prior to installation onto a 7 inch stroke shock. Set ride heights with the dual jam nuts not contacting the slider assembly. Adjust the jam nuts to achieve a 1.5 inch gap between the jam nuts and slider assembly after ride heights have been set. This set-up provides a 254 #/inch spring rate at corner entry and a 700 #/inch rate at corner exit, which works well in slick conditions to help eliminate loose corner entry deceleration handling and to improve forward bite off the corners. If necessary, you can increase the gap up to approximately 2 inches in .250 inch increments to loosen corner exit handling. You can decrease the gap to tighten corner exit handling. This setup also helps to keep right front suspensions from bottoming out during cornering.
AFCO Dual Stage Coil-Over assemblies use two coil-over springs, a special nylon slider for small body shocks or a nylon/aluminum slider for big body shocks that fits between the two springs. Also, two special, thin-walled nuts are used to jam the slider assembly in order to stage suspension stiffness.
When the slider assembly (located between the two springs) is free to slide on its shock, the Dual Stage assembly produces a combined spring rate softer than either rate of the two springs used (see combined spring rate formula below).
Spring Rate Formula: Dual Active Springs
Primary Spring Rate X Secondary Spring Rate
Primary Spring Rate + Secondary Spring Rate = Actual Spring Rate
Example: 200#/in. X 400#/in. 80,000
200#/in. + 400#/in. = 600 = 133.33#/in.
Note: The combination of a 200#/in. and 400#/in. spring works the same as a single 133#/in. spring, as long as both combination springs are active.
However, the spring rate of the Dual Stage assembly stiffens to that of the primary spring, which remains as the sole, active spring whenever the slider assembly contacts the adjustable Dual Stage jam nuts.
*This set-up information applies specifically to dirt late model race cars and in general to other types.