i have a 2010 Ralliart sportback do i need booth front and back sway bars ?
White line says a rear sway bar is good enough ???

 

You can be very happy with just the rear sway bar.

 

Yep, rear does wonders to the car from what I hear

 

Depends on how you want the car to handle. If you want it to handle like stock only with more stiffness then you will have to replace both. If you want less understeer, you can be just fine with the rear. Personally I like it with the 24mm rear and stock fronts.

 

just the rear really improved the handling - made it more neutral rather than excessive understeer!