Sway Bar

[Captain Snooze]

Originally Posted by Carlitoz3

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.

[Floggin Tires]

Originally Posted by Captain Snooze

I win the avatar

Yup.
Only with custard.

[steve99]

Originally Posted by babykwiss

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

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

[babykwiss]

Originally Posted by steve99

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.

[rs999]

Originally Posted by steve99

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

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.

[Ubersuber]

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....

[FastWhite]

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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[FastWhite]

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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[Captain Snooze]

Originally Posted by Ubersuber

Reason is the FRS is a bit soft in the front relative to the rear.

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

[steve99]

Originally Posted by FastWhite

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.



Sent from my iPhone using Tapatalk

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 :-)

[FastWhite]

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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[steve99]

Originally Posted by babykwiss

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

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

[Ubersuber]

Originally Posted by Captain Snooze

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

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.