What Sway Bars Work Best For You?

[racingfool]

Originally Posted by Racecomp Engineering

We've used OEM 18 front 14 rear, Whiteline 20 front 16 rear, Whiteline 22 front 16 rear,
Whiteline 20 front stock rear, RCE 25.5 front and 18 rear (hollow, so really 22 front 16 rear).

How much spring rate do sway bars add?
Are people typically getting 10% of their roll stiffness from bars? More? 15% - 20%?

Originally Posted by prandelia

has some real spring rate under the car, it needs it!

What spring rates/bars would you recommend on an STX autocross car on 200TW tires?

[86MLR]

With the MCA springs of 6kg front, 4.5 rear and stock bars, my car was pretty sweet on Hankook RS4's for both street and the occasional autocross.

If I was more serious about autocross I would maybe dial in a bit more oversteer.

Meh, compromises.

I also swapped the RS4's for RE003's, bad move by me.

RE003 are rubbish compared to the RS4's, and by rubbish, I mean rubbish, the RS4's are better everywhere, except when it's wet, the RE003's are "slightly" better, but not worth it in the end.

Lessons learnt and all.

[Racecomp Engineering]

Originally Posted by racingfool

How much spring rate do sway bars add?
Are people typically getting 10% of their roll stiffness from bars? More? 15% - 20%?

A whole heck of a lot more than 10% at least from the factory.

I think the OEM bar is more than 50% of the total wheel rate up front with stock springs. It's in my notes. Less than 50% for the rear since the bar is small and the motion ratio of the bar is lower.

- Andrew

[M0nk3y]

Originally Posted by Racecomp Engineering

A whole heck of a lot more than 10% at least from the factory.

I think the OEM bar is more than 50% of the total wheel rate up front with stock springs. It's in my notes. Less than 50% for the rear since the bar is small and the motion ratio of the bar is lower.

- Andrew

Karcepts Front Bar Rates:
Hole 1/1 = 299 lbs/in
Hole 1/2 = 323 lbs/in
Hole 2/2 = 346 lbs/in
Hole 2/3 = 375 lbs/in
Hole 3/3 = 404 lbs/in
Hole 3/4 = 440 lbs/in
Hole 4/4 = 475 lbs/in

Mann Engineering Rear Rates:
Hole 1 = 75 lbs/in
Hole 2 = 53 lbs/in
Hole 3 = 43 lbs/in

I have rear BRZ/FRS Bar (14mm) at 111 lbs/in
rear 86 bar (15mm) at 146 lbs/in

[Racecomp Engineering]

Originally Posted by M0nk3y

Karcepts Front Bar Rates:
Hole 1/1 = 299 lbs/in
Hole 1/2 = 323 lbs/in
Hole 2/2 = 346 lbs/in
Hole 2/3 = 375 lbs/in
Hole 3/3 = 404 lbs/in
Hole 3/4 = 440 lbs/in
Hole 4/4 = 475 lbs/in

Mann Engineering Rear Rates:
Hole 1 = 75 lbs/in
Hole 2 = 53 lbs/in
Hole 3 = 43 lbs/in

I have rear BRZ/FRS Bar (14mm) at 111 lbs/in
rear 86 bar (15mm) at 146 lbs/in

Sounds about right. And remember that the swaybars have their own motion ratio, which is much higher in the front than it is for the rear.

- Andrew

[BlueWhelan]

For what it is worth, when I did the math last year I arrived at the following OEM 2013 BR-Z rates at the wheels (not including dampers):

Front
Springs: 138 lbs/in
Sway Bar: 126 lbs/in

Rear
Springs: 110 lbs/in
Sway Bar: 28 lbs/in (36.5 lbs for PP 15mm)

So yeah, front is getting nearly 48% of its spring rate from the sway bar. In the rear its more like 20%.

Performance Pack numbers are obviously different.

To the OP's original question, I run the Performance Pack suspension (including rear SW) with the stiffer 2013 brz rear springs, and a 19mm Perrin front bar. Love the setup with -2 front camber. For a street car and my application, the chassis SINGS through corners.

[racingfool]

Originally Posted by Racecomp Engineering

A whole heck of a lot more than 10% at least from the factory.

I think the OEM bar is more than 50% of the total wheel rate up front with stock springs. It's in my notes. Less than 50% for the rear

And it appears STX guys are going with similar percentages?

Thanks for the info gentlemen.

[ROADRACER]

Originally Posted by doodoobrown

Just curious what everyone’s been liking for the track?

I’m running Perrin 22mm front SBs and stock rears but I’m running into understeer (I’m sure there’s driver error too). Thinking of going back to the stock fronts.

It makes sense that the cars balance would change to more understeer with only a stiffer front bar installed. Its not a driver error thing. Install a stiffer rear if you like the reduced body roll, or go back stock.

[scion fr-s]

Originally Posted by doodoobrown

Just curious what everyone’s been liking for the track?

I’m running Perrin 22mm front SBs and stock rears but I’m running into understeer (I’m sure there’s driver error too). Thinking of going back to the stock fronts.

I have Whiteline adjustable sway bars front and rear! I am running 20 mm up front and 16 mm in the rear.

[solidONE]

Originally Posted by M0nk3y

Karcepts Front Bar Rates:
Hole 1/1 = 299 lbs/in
Hole 1/2 = 323 lbs/in
Hole 2/2 = 346 lbs/in
Hole 2/3 = 375 lbs/in
Hole 3/3 = 404 lbs/in
Hole 3/4 = 440 lbs/in
Hole 4/4 = 475 lbs/in

Mann Engineering Rear Rates:
Hole 1 = 75 lbs/in
Hole 2 = 53 lbs/in
Hole 3 = 43 lbs/in

I have rear BRZ/FRS Bar (14mm) at 111 lbs/in
rear 86 bar (15mm) at 146 lbs/in

Guys that run big front bar and small rear. What's keeping you from running higher front coil spring rates instead?

On stock components pieced together. BRZ front, FRS Rear springs rates off the first generation and newer shocks. I've gone with a 19mm perrin and felt too 'pushy' for my use even at the softer setting. I'm sure its much different for autocross use and with double or triple the spring stiffness.

I do like the idea of soft rear sway bar or even delete as Robispec ran back when this car just came out. With stock springs it would just bottom out without the rear sway. Really good traction on the throttle before it hits the bumpstops tho.

[strat61caster]

What's alignment? Car isn't that pushy if you get the front tires on the ground so they're happy.

Most of these cars are setup around how aggressive owners are willing to align it.

[solidONE]

Originally Posted by strat61caster

What's alignment? Car isn't that pushy if you get the front tires on the ground so they're happy.

Most of these cars are setup around how aggressive owners are willing to align it.

At the time I ran this -3f/-2.3r degree camber and played with various toe in and out settings in the front on RS-3/RSR tires. I've since taken it off, but considering playing with it some more. As soon as I get the valving on my dampers to what I like, they'll be going back on the car as well.

I also tend to drive using generous amount of trail braking. I need to work on that.

[BlueWhelan]

Originally Posted by solidONE

Guys that run big front bar and small rear. What's keeping you from running higher front coil spring rates instead?



On stock components pieced together. BRZ front, FRS Rear springs rates off the first generation and newer shocks. I've gone with a 19mm perrin and felt too 'pushy' for my use even at the softer setting. I'm sure its much different for autocross use and with double or triple the spring stiffness.



I do like the idea of soft rear sway bar or even delete as Robispec ran back when this car just came out. With stock springs it would just bottom out without the rear sway. Really good traction on the throttle before it hits the bumpstops tho.

As Strat asked, what camber are you running in front?

I run BRZ front and '13 rear springs as well with a Perrin 19...with -2 camber the front isnt that understeery.

The rear sway bar motion ratio is pretty mild compared to the springs, so if you soften (or remove) the rear bar it won’t take out that much spring from the system. You probably won’t be on the bump stops much more than you already are (given that these cars are already very bump stop active), however the balance will shift to even more understeer. If that’s what you are looking to avoid, then it’s probably not the best option. I’d say add more camber, depending on where you’re already at.

Edit: ah you beat me to the post and answered my question.


Sent from my iPhone using Tapatalk

[strat61caster]

I'm at -4 up front, so are others who are way faster than me.

Edit: car is sprung as soft as you can to get the roll stiffness to work out, I want it to soak up pavement imperfections, the front geometry seems to just love a stiff bar (relatively speaking when the baseline is stock setup). I try not to overthink it too much these days other than some black magic with the lump of an engine over the front and roll centers.