Sway bars

[Bluemustang]

So I decided to do a little bit more research last night and it confirms what Bmac was saying. The rationale for the front sway bars actually works in opposite of conventional theory of - more front bar= understeer. Because of the MacPherson strut design, there is an initial camber gain as the suspension goes into compression and the lower control arm moves down, but there is no additional arm pulling the knuckle in so after a certain point the camber gets pulled in eventually going positive. The sway bar reduces cornering loads into the outside tire which can help keep the camber in check, preventing it from entering the bad part of the camber curve. The result is more front grip and less understeer. Now of course with anything suspension related too much of a good thing can be also bad. You only need as much bar as your tire can handle. Too much front bar and it will actually understeer. The key seems to be to run enough front bar to prevent the lower control arm from going past horizontal which puts into the bad part of the camber curve where it pulls back in towards positive.

The rear sway bar - well I don't know the dynamics of it. But I think running a stiffer rear bar should compromise your rear traction to a degree and make the rear end want to come around. And in a front heavy, high power RWD car, the rear traction is at a premium. Properly setup the car should not understeer and you should be able to provoke oversteer giving you've added enough throttle.

Please correct me if I've gotten any of this wrong. ;-)

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[BmacIL]

So I decided to do a little bit more research last night and it confirms what Bmac was saying. The rationale for the front sway bars actually works in opposite of conventional theory of - more front bar= understeer. Because of the MacPherson strut design, there is an initial camber gain as the suspension goes into compression and the lower control arm moves down, but there is no additional arm pulling the knuckle in so after a certain point the camber gets pulled in eventually going positive. The sway bar reduces cornering loads into the outside tire which can help keep the camber in check, preventing it from entering the bad part of the camber curve. The result is more front grip and less understeer. Now of course with anything suspension related too much of a good thing can be also bad. You only need as much bar as your tire can handle. Too much front bar and it will actually understeer. The key seems to be to run enough front bar to prevent the lower control arm from going past horizontal which puts into the bad part of the camber curve where it pulls back in towards positive.

The rear sway bar - well I don't know the dynamics of it. But I think running a stiffer rear bar should compromise your rear traction to a degree and make the rear end want to come around. And in a front heavy, high power RWD car, the rear traction is at a premium. Properly setup the car should not understeer and you should be able to provoke oversteer giving you've added enough throttle.

Please correct me if I've gotten any of this wrong. ;-)

You got it.

With the S550, the car is so big and heavy that unless you're on a skinny front tire, the limit for front stiffness before inducing understeer is quite high. If you're on a wide front (285 - 305, and particularly a square setup), the stiffness is going to generally help. @SteveW has found this, I know. For a dual use car, this is good justification for a moderate increase in spring rate (BMR Handling/GT350R, and up to Steeda DR), with a big front bar. For a more focused car, the nicer coilover setups allow for 400+ lb/in front springs, but they are gonna be a lot less forgiving on the road. They can still ride reasonably with good valving and tuning, but it's not something even most of us would want to DD.

 

[Cardude99]

So if I am understanding this correctly, a front sway is worth it at medium or even stiff but maybe keep the rear sway stock or if you upgrade run on softest setting?

 

[BmacIL]

So if I am understanding this correctly, a front sway is worth it at medium or even stiff but maybe keep the rear sway stock or if you upgrade run on softest setting?

Generally, yes. It really depends on driving style and what tire setup you have on the car, too. If you have a wide, square setup, yes, absolutely.

 

[Cardude99]

Generally, yes. It really depends on driving style and what tire setup you have on the car, too. If you have a wide, square setup, yes, absolutely.

I was looking at the Steeda bars with mounts and endlinks in the future. Any thoughts on that running the front at a medium stiffness and the rear full soft? I should be on a square set of 285'by then.

 

[BmacIL]

I was looking at the Steeda bars with mounts and endlinks in the future. Any thoughts on that running the front at a medium stiffness and the rear full soft? I should be on a square set of 285'by then.

I'd just do the front bar unless you're going to run very stiff front springs too.

 

[Cardude99]

I'd just do the front bar unless you're going to run very stiff front springs too.

The Steeda dual rate magneride springs

 

[BmacIL]

The Steeda dual rate magneride springs

These ones?
https://www.mustang6g.com/forums/th...te-ultimate-handling-lowering-springs.108433/

Definitely just the front bar, IMO.

 

[Cardude99]

These ones?
https://www.mustang6g.com/forums/th...te-ultimate-handling-lowering-springs.108433/

Definitely just the front bar, IMO.

Yep those are it. Thank you for the info, just saved me some money, now would the endlinks and the mounts still be a good upgrade for the rear or just leave it alone?

 

[BmacIL]

Yep those are it. Thank you for the info, just saved me some money, now would the endlinks and the mounts still be a good upgrade for the rear or just leave it alone?

The stock links tend to bend with track use, so maybe a good idea while you're at it.

 

[strengthrehab]

I'm still battling with this and discussing it with others who swear by the "middle" front and full stiff rear with a very high rate rear spring, but maybe that helps?

I'm middle/middle on my bars (Pedders brand) and will probably leave them there until I really really push the car. I am intrigued about the middle/stiff front and soft rear, though.

 

[Schwerin]

So as somone thats got a daily PP1 they want to be be more of a fun corner carver/road hugger would you recomend R bars or the FP bars?

 

[Roadway 5.0]

I think the bottom line is you have to adjust your bars to where you like them for YOU, and adjustable swaybars are indeed a good thing to have for just this reason. These bits are your last measure, fine tuning parts, that can totally change the dynamic of how your car handles and how inputs to the steering wheel transpose to the car's movements.

There is certainly some finite engineering and math to the equation. You certainly cannot go too stiff for a wheel rate, but there is a fine-line threshold of where you as the driver can maneuver the car better with some settings as opposed to a sloppy or over aggressive setting.

In the end, I recommend to get adjustable bars if you feel the need to change them at all. For me, an adjustable rear suffices to get the dynamic I want without the hassle of removing and reinstalling a front bar (I have a PP front, Steeda rear with 225lb/inF 880lb/inR Ultralite springs). For others, it may be different.

 

[strengthrehab]

I already talked to BMacIL about this, but if anyone is interested, I heard back from Pedders regarding their bar rates:
Pedders 35mm Front Bar:
455
492
530
Pedders 25mm Rear Bar
170
197
224

With my bar settings in the middle front and rear:
Front is similar to BMR stiff setting: 492 (Pedders) vs 501 (BMR)
Rear is similar to BMR soft setting 197 (Pedders) vs 200 (BMR)

 

[BmacIL]

I already talked to BMacIL about this, but if anyone is interested, I heard back from Pedders regarding their bar rates:
Pedders 35mm Front Bar:
455
492
530
Pedders 25mm Rear Bar
170
197
224

With my bar settings in the middle front and rear:
Front is similar to BMR stiff setting: 492 (Pedders) vs 501 (BMR)
Rear is similar to BMR soft setting 197 (Pedders) vs 200 (BMR)

Chart updated with the Pedders bars.

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