School me on swaybars vs. understeer/oversteer - Ford Mustang Forum
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post #1 of 45 (permalink) Old 12-05-2012 Thread Starter
klp
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School me on swaybars vs. understeer/oversteer

I have a '12 Brembo GT, great car but like many I want a little more performance without much ride quality sacrifice. I have looked at many suspension options and continue to look around before I pull the trigger.

Many of the more complete handling kits, FRRP comes to mind - include swaybars which claim to help handling. I understand that the stiffer bushings will likely deflect less and give more road feel, but what is the bars relation to over/understeer?

I have not tracked my car but have access to an open lot to play around. I know there are likely a lot of variables but my car seems to understeer at lower speeds, that tendency seems less the faster I go. Maybe this is because I am more likely to throttle up, I dunno.

Are the FRRP swaybars going to help my car handle better? Will it under or oversteer more? I know some are adjustable, how do they relate to initial turn in? Is it even worth the $ over the stock Brembo stuff?

Sorry if this is an overused topic, I have looked around a lot and not found too much.

Squidd posted some great information regarding dampers, stiction and their relation to plushness in suspension travel. I was wondering how swaybars factor into the overall handling picture.


'12 Brembo GT - 6MT, 3.73's, Shaker 1000, HID/Security, Comfort package, Steeda CAI, SCT tuner, Borla axle backs, Barton shifter+bracket, Steeda UCA+mount.

Last edited by klp; 12-05-2012 at 05:15 PM. Reason: Another question
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post #2 of 45 (permalink) Old 12-05-2012
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almost any aftermarket piece is better than stock...rear sway bars prevent understeer...
the stock bushings are notoriously weak, soft, so even replacing those will improve handling/feel...it's a cost issue, and well, this is Ford we're talking about so do the math
I have great aftermarket Maximum Motorsport stuff on my Stangs...a world of improvement if you have the loot

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post #3 of 45 (permalink) Old 12-05-2012
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my understanding is that a stiffer anti-sway bar on the front shifts the balance toward understeer ;

a stiffer anti-sway bar on the rear shifts the balance toward oversteer

and all of this only matters when you are at the limits of adhesion and either the front wheels push (understeer) or the rear wheels slide out (oversteer)

so you want the right balance of front and rear anti-sway bar stiffness to produce the balance of under/over steer that you want

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post #4 of 45 (permalink) Old 12-05-2012
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A rule of thumb is that anything you stiffen, will tend to make it push first. In other words, when you stiffen the rear, you increase oversteer; and when you stiffen the front, you increase understeer.

All that a sway bar does is increase effective spring rate when the wheels it joins are moving independently. For example, they don't increase spring rate as you drive over a speed bump and both wheels move in unison. But they do increase spring rate on the outboard wheel in a high speed turn when the car starts leaning over.

They are a tuning tool just like anything else. Most people want a suspension that is stiff enough to manage the dynamics of the wheels and the car at speed, but soft enough to be comfortable in normal street use.

I will tell you that (IMO) the stock bars are pretty big and do a good job of keeping the wheels planted. If you are planning on very high-G maneuvers such as those in autocross and road racing, you might try out a couple of different bars to dial-in body roll and grip.

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post #5 of 45 (permalink) Old 12-05-2012
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my understanding is that a stiffer anti-sway bar on the front shifts the balance toward understeer ;

a stiffer anti-sway bar on the rear shifts the balance toward oversteer

and all of this only matters when you are at the limits of adhesion and either the front wheels push (understeer) or the rear wheels slide out (oversteer)

so you want the right balance of front and rear anti-sway bar stiffness to produce the balance of under/over steer that you want
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A rule of thumb is that anything you stiffen, will tend to make it push first. In other words, when you stiffen the rear, you increase oversteer; and when you stiffen the front, you increase understeer.

All that a sway bar does is increase effective spring rate when the wheels it joins are moving independently. For example, they don't increase spring rate as you drive over a speed bump and both wheels move in unison. But they do increase spring rate on the outboard wheel in a high speed turn when the car starts leaning over.

They are a tuning tool just like anything else. Most people want a suspension that is stiff enough to manage the dynamics of the wheels and the car at speed, but soft enough to be comfortable in normal street use.

I will tell you that (IMO) the stock bars are pretty big and do a good job of keeping the wheels planted. If you are planning on very high-G maneuvers such as those in autocross and road racing, you might try out a couple of different bars to dial-in body roll and grip.
^^^^^^^^^^What they said Most cars have some understeer "built in" to the stock suspension. That is easier for most people to deal with then oversteer. I took my 2011 Mustang V6 to a high performance driving school last summer. Where the car lost traction, it had a little understeer (It had KONI Yellow Sport adjustable dampers). Easier to correct that. You really have to be on a course that lets you take the car to the point of losing traction to try to "balance the car" at speed and some turning radius. One would expect most of the "fixed sway bar sets" will try to push the car closer towards neutral, without taking it to "oversteer." On the adjustables you are really on your own to test and verify.

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post #6 of 45 (permalink) Old 12-05-2012
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Many of the more complete handling kits, FRRP comes to mind - include swaybars which claim to help handling. I understand that the stiffer bushings will likely deflect less and give more road feel, but what is the bars relation to over/understeer?
I'm going to assume that the bushings you're talking about here are the bushings for the sta-bar and not for the control arms or the PHB. "Sta-bar" being shorthand for stabilizer bar, which is this part's correct name (common usage notwithstanding).

In a nutshell, as you stiffen the front bar (leaving everything else alone), you increase understeer. Likewise, stiffening only the rear bar reduces understeer.

Sta-bar bushings effectively reduce the effectiveness of the bar itself (it's a "springs in series" thing).


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I have not tracked my car but have access to an open lot to play around. I know there are likely a lot of variables but my car seems to understeer at lower speeds, that tendency seems less the faster I go. Maybe this is because I am more likely to throttle up, I dunno.
I'm guessing that you're guilty of overdriving at the slower speeds. Cranking the wheel over too fast (tires can't quite keep up), going in too hot, staying on the brakes, etc.

Geometrically, a tight turn gives away more camber than a wider turn does, and you may not even have enough static negative camber dialed in to the car to begin with.

Tire inflation pressures - there are better settings than Ford's 32f/32r. Trust me.


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Are the FRRP swaybars going to help my car handle better? Will it under or oversteer more? I know some are adjustable, how do they relate to initial turn in? Is it even worth the $ over the stock Brembo stuff?
Personally, I wouldn't ever get a non-adjustable bar when adjustable versions are available.

Kits that lack adjustment ask you to accept somebody else's definition of "improved handling" - and which need to consider a wider range of driver skill level. IOW, they'll tend to be a little on the conservative (understeerish) side.



I'm really new here, but not to the "corner-carving" stuff.



Norm

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post #7 of 45 (permalink) Old 12-05-2012
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I'm shocked you came over here Norm. I see you in the 'corner carver' section at S197 quite a bit so I agree with your post.




...swaybar is just as accurate as stabilizer bar btw, and shortens a lot better too.
post #8 of 45 (permalink) Old 12-05-2012
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These are the swaybars I recommend:
2011-2012 Ford Mustang Anti-Roll Sway Bar Kit 35125.320 - UPR Products

Upgrading the swaybars makes a huge improvement in handling. The adjustable swaybars are nice too. (the front one is three way adjustable) Adjusting the bar makes a difference you can feel.

For example, when I had 275/40-18s all the way around, the handling balance was perfect, but when I switched to a staggered tire sizing, the car picked up some understeer. I softened the front bar and it balanced the handling. It's a nice tuning aid!


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post #9 of 45 (permalink) Old 12-05-2012
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I'm shocked you came over here Norm. I see you in the 'corner carver' section at S197 quite a bit so I agree with your post.
I'm keeping an open mind.


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...swaybar is just as accurate as stabilizer bar btw, and shortens a lot better too.
Yeah, "sway" probably does roll off the tongue a little easier.

But some years back, I knew a guy who had worked at Roush, and "sta-bar" was the industry-insider shorthand (sway is not the same thing as roll, and if you google "trailer sway bar" you'll find an entirely different thing)


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So if I have tires in 255/40/19 front and 275/40/19 back, which rear sway bar do you recommend to keep the car well balanced.

Judging by the fact that you have 19" wheels(and this in no way implies anything negative btw) tells me you won't be pushing 10/10ths at the racetrack. If I were you, I would run the stock setup until you find exactly how your car responds to the way you drive and go from there. You can't throw parts at the car and assume they are going to make the car respond the way someone over the internet tells you it will.

Upgrading to quality shocks will 99% of the time be an improvement over stock. However swaybars(aka sta-bar to Norm) can have a dramatic and even a negative effect on handling, especially to someone without the necessary prior track experience both in general and with that particular car setup and track.
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Judging by the fact that you have 19" wheels(and this in no way implies anything negative btw) tells me you won't be pushing 10/10ths at the racetrack. If I were you, I would run the stock setup until you find exactly how your car responds to the way you drive and go from there. You can't throw parts at the car and assume they are going to make the car respond the way someone over the internet tells you it will.

Upgrading to quality shocks will 99% of the time be an improvement over stock. However swaybars(aka sta-bar to Norm) can have a dramatic and even a negative effect on handling, especially to someone without the necessary prior track experience both in general and with that particular car setup and track.



TNX GRIMACE!! BTW got the DW extreme contact per your recommendation (not on yet until the spring). As to I have Koni yellow so shock wise Im covered pretty well.

You are right about track. Only 2 times last year.
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TNX GRIMACE!! BTW got the DW extreme contact per your recommendation (not on yet until the spring). As to I have Koni yellow so shock wise Im covered pretty well.

You are right about track. Only 2 times last year.

Hey, I'm still working on my first track day so I can only offer general advice. The experienced guys here can offer the more direct advice regarding suspension setups, but the best information you can arm yourself with is direct feedback between you, the car, and your instructor(<-which even experienced racers appreciate).
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Originally Posted by Grimace427 View Post
Judging by the fact that you have 19" wheels(and this in no way implies anything negative btw) tells me you won't be pushing 10/10ths at the racetrack. If I were you, I would run the stock setup until you find exactly how your car responds to the way you drive and go from there. You can't throw parts at the car and assume they are going to make the car respond the way someone over the internet tells you it will.

Upgrading to quality shocks will 99% of the time be an improvement over stock. However swaybars(aka sta-bar to Norm) can have a dramatic and even a negative effect on handling, especially to someone without the necessary prior track experience both in general and with that particular car setup and track.
just curious what wheel size has to do with how hard you push it on the track?

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Originally Posted by Grimace427 View Post
...swaybar is just as accurate as stabilizer bar btw, and shortens a lot better too.
sorry for nitpicking, but it is an ANTI-sway bar, meaning it prevents or reduces sway ; a "swaybar" would increase sway which isn't really what we want

but anyway yeah we know what we mean in the common vernacular


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