Perrin sells a rear bar upgrade. 16, 19, or 22mm.

If your basing suspension mod decisions on driving the stock tires, don't. The car feels much more planted with a good tire/wheel upgrade.

It's going to be a good while before I get to sway bars, proper coils and alignment are first.

BUT is anyone like Hotchkis making matching F&R adjustable sways. I can see it for autoX, but for the track I can't see just a stiffer rear bar without a matching stiffer front.

I would never replace one sway bar.

I prefer to stiffen the front and rear to get the handling and G's

I guarantee that Hotchkis will come out with a front and rear sway bar. ;) Along with springs and bracing components. It will be important to upgrade the front AND rear sway bar for proper handling balance.

It will also be good to choose springs that will work with the sway bars you upgrade to. Hotchkis will design their sway bars and springs to work together as a total system. Based on the low grip of the OE tires, higher performance tires will be recommended when upgrading springs and sways.

And for those coming from an AWD platform, swaybar tuning is very different in a RWD, its basically the opposite. With STi/WRX and Evo the basic tendency is to get as much front end grip as possible and then get the rear as loose as possible so the car will turn. Front end grip is still important on the RWD but you don't have to fight as much to get the rear active. If anything, compared to AWD, its too active already!

To decrease oversteer (common in RWD) you'll need to go to a larger front bar and/or smaller rear bar. A larger rear bar, in general will increase oversteer on an already oversteer "prone" car.

As Andrew from RCE alludes to, the spring rates on the FRS are different to the BRZ, with the FRS having a softer front spring compared to the rear making it more tail happy compared to the BRZ (out of the box). So increasing the size of the rear swaybar on an FRS will have a different effect to the BRZ.

Alignment will also have an effect on oversteer tendencies. Especially since this platform seems very responsive to subtle alignment changes. But in general, to decrease oversteer, less neg camber up front and more neg camber in the rear. More neg camber in the rear will give more grip to the rear tires in a turn.

But at this point, exact figures (alignment, sizes of bars, spring rates) are purely theoretical. They will depend completely on lots of factors like tires, component mixes and ultimately, driver preference. Its really a very exciting time because we are all just trying to figure out this new car. There are lots of basic assumptions we can make but the fine tuning will be fascinating to watch. Hopefully all the vendors stay transparent with their findings and opinions.

Good post! This car is so sharp that minor differences can have a big effect. A 16mm rear bar with a very mild or stock alignment will be fine for some, whereas it might be a bit too much for an FRS that simply has a slightly more aggressive alignment. Once front bars come out for this car I think you'll see people go with something along the lines of 22mm front and 16mm rear, or around there. But....that will depend on everything else with the car. Before it's "just get the piggy Impreza to turn!" Now it's "help the car turn AND keep it stable!" Still testing to do.

- Andrew

I would optimize camber before settling on sways. Getting some front camber in will increase front grip tremendously, to the point that you might want a stiffer front bar rather than rear.

My approach: Maximize camber (to a point, but stockish setups are usually camber-limited), minimize toe, balance with roll stiffness via sway bars (assuming reasonable ballpark-for-usage springs already installed).

I agree, and I see swaybars as sort of a final step tuning tool. There is the big bar with soft springs approach that was common on Impreza and that was okay sometimes when it was thought through clearly. I don't know if it's the right way to go with this car though.

- andrew

Does any one know if there is a compatible hollow front sway out on the market yet?
For us who are competing in SCCA Stock class, we can only change/remove one sway bar.
Hollow would be ideal just due to the weight.

I have read that the OEM BRZ/FRS Rear anti-roll bar is 14mm in diameter. I assume it is solid.

What is the OEM front anti-roll bar's outer diameter? Is it the same on the FRS and BRZ? Has anyone determined what the wall thickness is at this point?

Thanks!

18mm front, 14mm rear. solid.

Not yet....;)

- Andrew

Thanks for the reply!

I can tell you that with -2 camber in the front an FRS is very tail happy. It made me remove the rear bar.