So I have some coilovers on order but I still have the stock sway bars. Should I upgrade the sway bars as well or are they not needed? If needed which ones? ST or Racing Beat?

 

It depends what you're using the car for, and how you're going to set your coilovers.

I only drive my car on the street. I upgraded to an RB front and ST rear anti-sway bar. I've got stock S4 links with urethane bushings. My car is also equipped with Tein 1" lowering springs.

I think the ST rear bar is too stiff for street or grip driving. It might be ideal for drifting though. On any given day my car weighs more in the rear than it does in front. It's a bit "twitchy" in the rain, but once it goes into a slide it's very controllable. If I'm in the dry, it's very predictable, but with the lowering springs it's a bit rough.

My car has DTSS eliminator bushings and a properly de-powered S4 GXL steering rack with a welded quill. I haven't properly adjusted any of my wheel alignments, save for front caster. Looking at the car, I've got too much rear negative camber- this might explain the rear twitch it has in the rain. I know a stiff rear bar doesn't help tho.

 

Yeah I guess that would be helpful I must've had my other thread on my mind where I answered that but then didn't link to it. Duh.
For now just driven on the street. If this racetrack actually gets built in a neighboring county I may do track days but that's years away if ever I'm sure. The coilovers are Redshift Racing's BC competition coilovers Basically BC racing coilovers with some internal parts replaced and Redshifts own custom valving for racing. they are meant for racing but Redshift tells me even on the street they feel better than the off the shelf coilovers. Says their valving allows the running of a softer spring so I'm starting pretty soft for a coilover at 6kg/4kg. F/R
I have the Mazdatrix Sway bar links on the rear. I had them on the front but after 20 years one of them had siezed up so I put the stock ones back on. I got some new Heim joints from Summit so I'll be going back to the Mazdatrix style links eventually.

 

there is an SAE paper on the FD body design, and they basically put an FC on a jig and measured how much the body moved as they took stuff off. removing the sway bar actually helps body rigidity, its so far in the front that it just bends the chassis.
also if you compute the spring rates at the wheel, compared to the springs the sway bars do very little.

in conclusion spend you money on something else Autocross to Win (DGs Autocross Secrets) - Dynamics Calculator

 

Choosing sway bars depends on how the car drives.

My current fc setup is a bunch of suspension stuff, all heim joints, and the stiffer part shop max coilovers.

I use the car for drift but used to daily drive it and take it up mountain roads. I do not run a front sway bar. With the steering angle I have, a fc front sway bar will not fit. I run a RB rear sway bar with adjustable heim joint endlinks.

I adjust the endlinks to adjust how the rear end swings out and how it will allow me to transition the drift to the other side.

ive adjusted the rear sway bar endlinks to the point the car would drift and rear end slide out, but it wouldn’t want to transition the other direction. So I readjusted the links to get exactly what I wanted.

For my 06 sti, I run Tein flex z coilovers. I installed a 27mm front sway bar (stock is 20mm). steering feedback improved but induced understeer. I then installed a 24mm rear sway bar (20mm stock), and it neutralized out the understeer.

Basically what I’m saying is you pick sway bars based on how you want the suspension to react. Stiffer front creates understeer. Stiffer rear creates oversteer. It’s all a balancing act.

 

All in all, install the coilovers and go drive the car and get used to the handling characteristics. Then you will know if you need to upgrade the sway bars.