I also currently have s-tune suspension on mine. Lower than standard. Would rather mine lower, but it is a happy medium, and the car is still very useable. Ie speed bumps etc.
Heres a write up I found somewhere, can't remember where, but I saved it a while ago.
Nismo suspension
Brand : NISMO
Product: S-Tune Suspension System Kit Silvia S15
Part Num: 53110-RSS55
Suspension:
- Normal shape
- Short Stroke Type
- Fixed Dampening Type
- Reinforced rubber upper mount on the front struts.
Suspension Spec:
- Damping Force 0.3m/sec, N(kgf) Front 2157/785 (220/80) Rear 1765/834 (180/85)
- Spring constant N/mm (kgf/mm) Front 44.1(4.5) Rear 53.9(5.5)
- Vehicle height change Front~ -20mm Rear~ -20mm
Features:
-A Unique design, for all models.
To develop the suspension, the amount of the stroke, different in each model, has been perfectly adjusted. The damping force was the balance by using the best springs. The upgrade were not only external, the amount of oil, the length of the case, and the lengths of the rods are fine tuned down to the last millimeter. a truly unique design was executed for each model, sparing no detail. Moreover when a normal shape is selected, for instance, not to counterbalance the horizontal stress by the inclination of Strut by the offset spring layout in the strut type, an improvement of durability and decrease of the friction are achieved.
-Vehicle riding height, for optimum racing performance.
The improvement of the sports driving performance is closely linked to the amount of the stroke available. With the NISMO suspension the center of gravity is lowered, and overall riding height is lowered*. The suspension characteristic never changes, even if the number of passengers changes, this is due to the huge amount of the stroke this suspension provides. Moreover, the strain on the suspension bush and the body is decreased by employing a rubber bush to the upper mount, the advantage of which is long-term maintenance free vehicle condition.*It will be lowered down about 20mm, though it will differ of each model.