Base case specifications :

The springs will be matched with adjustable Koni sport shocks in the front. I already have Tokico rear shocks in good shape in the rear of the car. I’ll keep them. The damping of the Tokico beeing not adjustable and tuned for after market lowering spring, the spring rate must be kept in the 150-160lbs/in in the rear. The front will have to match even if the Koni can be adjusted for spring up to 300lbs/in.

Fearing too much oversteer from Case 1 and 3, Case 2 is selected.

 Selecting a spring length

 Coilover springs are available in 10 and 12in length. Calculated static deflection is 4in. but installation shows a 3.5in static deflection. Car is weigth must be overestimated or unsprung weigth under estimated.

 10in-175lb/in Afco made spring have a maximum stroke of 6.3in before coilbind. Since static deflection is 3.5in, only 2.8in of suspension travel is left before coilbind. The suspension bottom must be a rubber bumpstop. It must not be coilbind. If coils bind, spring seats may break or strut tower may rip. Shocks must not bottoms either. Thus a 10in-175lb/in spring in the front requires a least a 1in drop in ride height to prevent coilbind.

 A 12in-175lb/in springs in the front allow the car to have its normal ride height without coilbind but the maximum drop is about 1in.

 At the rear, the problem is similar. 10in-150 lbs/in springs require at least a 1in drop to prevent spring bind. 12in-150 lbs/in springs is correct the maximum drop is 1inch.

 Usual spring rate are in increment of 25lbs/in. But Afco also offer a 12in-160lbs/in spring. The final spring choice is 12in-175lb/in springs for the front and 12in-160lb/in springs at the rear.

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