On a smooth, straight, road, your car should be stable at any speed it can reach. If it's not, check the tire pressures and wheel alignment, especially the rear toe settings. The S2000 is very unstable at speed if it doesn't have enough toe in at the back. Corners at higher speeds present another problem, becuase there is a lot of rear lift at high speed, which increases the car's tendency to over steer (and over respond to steering inputs).

A good rear wing can help cancel the rear lift. More rear toe-in *might* help over bumpy surfaces.

 

Get a high rise rear wing, front splitter and front/rear bumper canards.

 

get the apr rear diffuser is functional , not that big like the jc and cost less... is like 500$

 

CR lift is reduced 70%.

PERFORMANCE FEATURES:
Skidpad pulls .95G
Slalom speed 71mph
Coefficient of lift reduced approximately 70% over original S2000
Over 2-seconds per lap faster around Japan