Sway Bar
 

Was wondering how sway bars would affect the handling of the car. My current setup is

17x8 with 225/45/17 hancook rs3 v2
Whiteline camber bolts
Front and rear centric rotors with HP+ pads
Front is about -1.4 camber with 0 toe
Rear is about -1.2 camber with 0 toe

The kit I'm thinking about purchasing is the eibach sway bar kit. Will it increase cornering grip and decrease body roll?

I've done 2 track days and I wanted to reduce body roll and increase cornering grip without going coilovers first.

Eibach Front 25mm solid vs OEM Front 18mm
Eibach Rear 19mm solid vs OEM Front 14mm

Thanks

They would definitely reduce body roll.

Many will say swaybars should only be used for fine-tuning balance but honestly they don't have to be limited to that. I think a set of swaybars for your uses will improve the car.

That said, those are pretty big bars.

- Andy

Thank you for the reply RCE. I decided to go with Eibach becuase i scored a really good deal with them. I really like the feel (for now) of the stock suspension, was just wanting less body roll with increased cornering grip. Is having such big bars a bad thing? I'm going to have to play around with the adjustments to still keep the overal neutral feel of the car.

I only put on the Strano 22mm bar:

http://www.stranoparts.com/partdetails.php?PartID=928
"This 4 pound 22mm tubular front sway bar for the Subaru BRZ and Scion FR-S is 1 pound lighter than stock, but stiffer. Stock is 18mm and 5 pounds."

I'll say that I'm really happy with only upgrading the front bar. I think it adds a little more responsiveness to the front while still allowing the rear to be a little more planted with the softer oem sway. That 25mm does seem kind of fat. If the front becomes too stiff then you could start to get understeer. I'm not sure where that point is with our car or if 25mm is close or not.

One thing I have learned is dont choose suspension based on scoring a deal. Luckily you are only on springs so a super stiff bar wont be as bad as if you were already on stiff coilovers. Hope it works out for you.

This is true and im not really about just buying cheap things. Like i mentioned before, I really enjoy the stock shocks/springs. judging by ur post, i guess its not good at all to run this setup with coilovers?

I personally dont have experiance with it but have done tons of research on peoples feedback on sways. It seems our car doesnt need a whole lot to begin with and it is easy to go too stiff when combined with coilovers. I am on RCE yellows and will be putting in Koni struts. I still cant decide if I will be wanting the RCE sways which are similar size but are hollow for fear its too much.

I know a few people personally and have read of multiple others who ended up downsizing sways after some time. Not saying that will happen but maybe do some research on how stiff they are at the varoous settings compared to stock and other bars.

@Racecomp engineeting do you have data for the for of the oem bars? Seems to not be a reliable answer out there.

Sway Bar
 

I have the Eibachs front and back, both set to stiff (there are 2 settings for each). Made a big difference in how responsive the steering feels and how flat it corners now. With that said, things are a bit more uncomfortable over bumps now and I occasionally have problems with driveways having a rear wheel in the air momentarily. So in summary, sways make a big difference in turning and onramps, but you lose some of the comfort of the stock setup.

If you aren't sure - start out with your sway bars as "soft" (short) as possible front and rear. They will most likely still be stiffer than stock. Go from there.

I'm not quite sure what you meant by this but the way I read it you are giving incorrect information.

Sorry - check your instructions for your specific type :)

I do not know what you mean by this. Specific type of what? To the best of my knowledge all makes of sway bars for BRZ/FR-S/86 work the same way.

Short = less leverage = harder


It's elementary leverage...

I'm also keeping my coils as is and wanted to get some sway bars as well.
Was actually thinking of going with TRD but these reviews you guys are giving seem really good.
So what's better, a heavier or lighter sway bar?

If you are using a sway bar as a boat anchor you want as heavy as possible.

It depends on what you are trying to achieve. Are you trying to reduce roll or change steering behavior?

Don't forget there is no free lunch. The heavier the sway bar the less independence your suspension has at that end.

Yup.
Only with custard.

Agree with the Race Comp Engineering guy those are pretty big increase over stock.

They will stop body roll alright but will make for a very uncompliant ride over anything but the smoothest of roads or track. Over bumpy corners it would likely become unsettled and skittish especially with stock dampers, might be best to talk to some others with bars that size or maybe go for something like

22 mm front
16 mm rear
preferabably adjustable , think whiteline do those sizes

Will def take that into consideration. Well then, if anyone has experience with these bars that has a simmilar setup, please chime in! Thank you everyone for the advice.

Makes sense. Perrin recommends running 19/16 F/R for their bars to get some flatness in turns but also to keep the most OEM ride.

I think adding stiffer bars makes more sense than increasing the spring rate which is already reasonably high for a street car.

Going that big however, may compromise your ability to get the meagre power down exiting corners, especially if the track isn't smooth. On the street you might find the handling a little alarming over any sort of bumpy curves.

The other thing is Whiteline, for example, recommends you consider just increasing front roll bar stiffness first. Reason is the FRS is a bit soft in the front relative to the rear. The BRZ is likely a little quicker on most tracks because the front roll stiffness is already higher (springs not roll bar).

My BRZ has 1.9 degrees negative rear camber (for street use) and I see you are only at 1.2. If you don't mind tire wear then increasing negative camber at the rear will be preferable to adding roll stiffness. Add a stiffer front bar (19 mm for example or as whiteline suggests 22mm) and if you get too much understeer dial in more negative camber at the front as well if you have adjustable front camber which it seems you do.

Only increase rear roll stiffness as a last resort if only because of the traction issues you can have if you try to put power and cornering power into the rear axle at the same time. Roll bars work by levering the outside spring (wheel actually but the effect is to add spring rate to one side and to the other side but the inside wheel spring rate addition reduces the drooping of the inside spring so does actually increase the spring rate on both sides at the same time) against the inside spring with the twist in the bar proportional to the force trying to lift the inside wheel, springs work independently of each other which is why you need twice the roll bar rate increase to deliver the same roll control as changing just the spring rate. Roll bars tend to lift the inside wheel more than increasing spring rate would. There's no free lunch in return for that smoother ride....

Remember that a 25 mm hollow bar is equivalent to about a 22mm solid bar. Per RCE website.
I'm running a 20mm solid bar Superpro front with Whiteline end links. Koni dampers. From stock with front bar only. I found balance excellent, good turn in, no under steer. Now with the Koni's, I'm at full stuff at the rear and 1/4 to 1/2 from soft in the front.


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Small phone for fat fingers.
This seems to be opposite to everyone else with the same setup. Thinking of putting the stock bar back on, but putting the yellow springs in.
I autocross the car. Last race I found braking hard on entry, slow in, settled it all down. I now had power out of the corners.
This is just an example of what happens when you do change the suspension balance. So research and be prepared for a change that will require additional changes.
That why the shops sell packaged deals.


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The rear is softer than the front. Don't forget motion ratio.

I have brz with Sti pink springs and just the adjustable 16mm rear bar on mid setting. Fixed up the bit of initial understeer brz has, will be different on 86. I dont do any trak work but its plenty stiff enough for street. If you have you rear shock on stiffest setting might be worth trying a slightly stiffer rear bar and backing off the rear shock stiffness.

Suspension setting / changes are so complex i dont claim to know much :-)

Most definitely. Just put the RCE Yellows on. If you have ever driven a top tier German car, 98 M Roadster, there suspension is very firm but supple. Very flat cornering, you know it's stiffer but supple.find it hard to put into words. Wonder why I didn't do it in the first place. But STX now. More money.


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Before you put massive sway bars on your car have a look at this chart of stiffness vs diameter is not a linear relationship (you also need to look at hollow vs solid ) but just to keep it simple assume they are similar construction and material

18 to 25mm front stiffness increase = 270%
14 to 19 rear stiffness increase = 240% increase

http://www.whiteline.com.au/docs/bulletins/BL-281.pdf

The reference is to the BRZ having stiffer front springs than the FRS. That is, the FRS is softer at the front relative to the rear than is the BRZ. Therefore, adding just a bigger front bar will make the FRS handle more like the BRZ, which in my opinion would make it faster than a stock FRS around most types of track and certainly faster on the road under normal conditions.

The motion ratio actually favours the front springs, i.e. the rear lower arm acts as a lever on the rear coilover so the effective rate of the rear spring is lower than its actual rate. Motion ratio on the front strut is closer to 1:1 than at the rear coilover.

Motion ratio also applies to the roll bar rate. The front roll bar drop link is on the strut itself and for practical purposes has the same motion ratio as the strut spring. At the rear the roll bar drop link is inboard of the coilover and so is even less effective than its diameter would suggest.

Put another way both the rear spring and the roll bar have higher spring rates than needed because of the point of action being some distance inboard from the hub. Changing these spring rates would have less effect at the back than at the front, important to remember when trying to match changes front to rear. Putting a bigger bar on the front will add more to the spring rate than adding the same relative increase to the rear.