Sway bar adjustments

jinthadell

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So I was changing my oil last night and realized I had the front swaybar set on its softer setting. I swapped it to the firmer setting and now the car feels completely different. With the back on firm and the front being on soft I’m guessing it was causing understeer. Seems to turn in a lot quicker
 
I think it works the other way. Stiffer rear bar helps correct understeer. Softer front bar likewise. So you are starting to feel quicker turn in or toward oversteer. Maybe now you like the steering response better. But how is the ride? Eibach recommends stiff for track.
 
Yes, stiffer rear spring rate increases rear slip angle, or more oversteer. Anti roll bar is basically a spring the only works in the roll axis. Stiffer rear coil springs and even higher rear tire pressure - relative to the front - also increases oversteer.
 
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Here's my favorite post on tire pressures :laugh:

I have a RWD GT with staggered 19" tire sizes and my tire pressures are (starting from LF going clockwise): 43, 42, 37, and 38. Recommended pressure is 36 psi for all 4.

I set them that way to account for the dynamics of corner load. During cornering and braking, the front tires carry more weight than the rears, so the front pressures are set higher (than the rears) to stiffen sidewalls and to reduce sidewall rolling; the rear pressures are increased just slightly to account for a higher average of cornering speed. During acceleration, the front tire pressures are less important; the modest increase in rear is also not that important.

The 1-2 psi difference in side-to-side pressures is to account for the difference in static corner weight. Usually in a mass-produced vehicle, the LF corner carries the most weight followed by RF, then LR, and the lightest at RR corner when there is only the driver in the car.
 
From interior to exterior to high performance - everything you need for your Stinger awaits you...
If you want to fiddle with tire pressure to correct understeer, you lower the rear tire pressure and/or increase the front tire pressure. thats according to these guys. Quick Tech: Oversteer vs. Understeer and How to Correct Both - OnAllCylinders
Unlike coil springs and torsion springs, there are actually two sets of dynamics at play with tire pressure.

On one hand, increasing tire pressure effectively increase the "tire spring rate". Pneumatic tires act just like a pneumatic spring, in very much the same way air springs (as used in air suspension) work. So, increasing the "tire spring rate" has exactly the same effect as increasing stiffness of coil spring or torsion spring (anti-roll bar) in countering lateral weight transfer. This correlation is a linear one regardless of range of tire pressure. Higher pressure = stiffer tire spring rate.

On the other hand, increasing tire pressure can affect how the contact patch interacts with the ground surface in generating lateral grip. This effect is not strictly a linear one:

1. At lower tire pressure ranges, decreasing pressure usually results in lost of traction/grip, which will allow the rear tires' slip angles to increase in a turn, which is the very definition of oversteer. This typically applies to the track environment, where tire pressures are typically run substantially lower than for street. So... in that sense, increasing rear tire pressure would increase mechanical grip and lessen oversteer.

2. However, at higher pressure ranges, which is more like what most of us would run on the road (as are the car mfr's typical recommendations), continued increasing tire pressure would actually decrease traction/grip, as the contact patch becomes less than optimally utilized. Over-inflating a tire will place more contact pressure in the center of the contact patch, thus under-utilizing the outer portions of the tire - leading to reduction of tire's effective grip. In that scenario, your rear end will become rather loose and lively... which could be good or bad, depending on the end goal.

Back when we used to AutoX VW Golf GTI's in the later '80s and early '90, we actually used this to counteract that car's tendency to understeer. We used to jack up the rear tire pressure quite high, so the car would rotate much easier.


Not the easy black-n-white answer some might hope for, but those are the intricacies of suspension tuning. I myself find it far more fascinating than stomping on the loud pedal like an angry ape... and far more satisfying when you do get it right, and the car goes around the turn exactly as you prescribed it.
 
So, the "On All Cylinders" guys are speaking from a performance / track perspective?
 
It rides great! Even on 255/35r20s, I’ve got no complaints. And I have the ARK bars.
 
So, the "On All Cylinders" guys are speaking from a performance / track perspective?
I would imagine most discussions on this topic are referring to racing or HPDE. Most road cars are setup with a fair amount of understeer for good reasons. For the vast majority of drivers, under most road conditions, it is safest to keep it that way. Even a neutral handling car can become a handful in the hands of unskilled drivers not accustomed to driving at the threshold of tire traction. To tweak a street car's cornering attitude by changing its tire pressure in a significant manner, the driver either really knows what he's doing... or he's heading into impending disaster.


BTW, forgot to mention one other tidbit on how increasing tire pressure could affecting handling... As mentioned above, doing so tends to stiffen "tire spring" and reduce tire compliance. That is, a tire's ability to conform to the rough/uneven/undulating road surface and maintain traction. This is especially true for large heavy wheels and very low profile wide tires. During hard cornering, the outside rear tire could possibly lose contact with the road surface and break traction. Even if the break is momentary, this could result in SNAP OVERSTEER, which is very difficult to recover. This is another reason I run 18"s. It is also why I avoid super wide rear tires just for the looks.

This circles the discussion back to this thread's topic... while stiffer springs (either coil or anti-roll bar) can improve cornering by reduce the effect of lateral weight transfer, that is only a net positive if the road/track surfaces are smooth. Over rough road/track surfaces, too stiff a suspension can lead to insufficient suspension compliance. The result is the wheel/tires can have a tendency to hop off the road/track surface and break traction. The gummiest and widest tire in the world won't give you any grip, if it is hanging in the air.
 
I would imagine most discussions on this topic are referring to racing or HPDE. Most road cars are setup with a fair amount of understeer for good reasons. For the vast majority of drivers, under most road conditions, it is safest to keep it that way. Even a neutral handling car can become a handful in the hands of unskilled drivers not accustomed to driving at the threshold of tire traction. To tweak a street car's cornering attitude by changing its tire pressure in a significant manner, the driver either really knows what he's doing... or he's heading into impending disaster.


BTW, forgot to mention one other tidbit on how increasing tire pressure could affecting handling... As mentioned above, doing so tends to stiffen "tire spring" and reduce tire compliance. That is, a tire's ability to conform to the rough/uneven/undulating road surface and maintain traction. This is especially true for large heavy wheels and very low profile wide tires. During hard cornering, the outside rear tire could possibly lose contact with the road surface and break traction. Even if the break is momentary, this could result in SNAP OVERSTEER, which is very difficult to recover. This is another reason I run 18"s. It is also why I avoid super wide rear tires just for the looks.

This circles the discussion back to this thread's topic... while stiffer springs (either coil or anti-roll bar) can improve cornering by reduce the effect of lateral weight transfer, that is only a net positive if the road/track surfaces are smooth. Over rough road/track surfaces, too stiff a suspension can lead to insufficient suspension compliance. The result is the wheel/tires can have a tendency to hop off the road/track surface and break traction. The gummiest and widest tire in the world won't give you any grip, if it is hanging in the air.
Dude you make me feel like a window licker....you are always super informative!! Thanks for the knowledge sharing. Much appreciated
 
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From interior to exterior to high performance - everything you need for your Stinger awaits you...
Dude you make me feel like a window licker...
LOL. I like sharing what I know, but I'm always a bit apprehensive how the techie spiels would be taken. I imagine most probably don't care to delve into the technical details and the finer points. Then I think... those that don't care will just skip over my post anyway, so it can't possibly offend them. OTOH, for those few who actually do like this sort of material, it's worth sharing perspectives that aren't usually found on these forums.

Glad to know there are some who find them useful. :)
 
Glad to know there are some who find them useful. :)
I don't how "useful" learning something is when it doesn't get used. I don't track. But I read all your posts on how you set up your Stingers for that with interest. Who knows, maybe someday I'll find it useful.
 
There's nothing wrong with more information in my opinion. Worst case it doesn't get used. Best case it's there when I need the reference.

That being said I like the balance of the Eibachs on the soft setting when just driving around. A little more turn-in and she seems well enough balance between over and understeer for Sport mode. Eco/Comfort seem similar but it feels like less rear-end push probably due to the power split--or it could be psychosomatic. :)

Stiff? I'm not sure about yet. I might play with stiff this summer. But then again I only tend to push her to the top of my driving ability when conditions are very good. I wouldn't be trying to drift into the dino dimension while it's raining on a public road.
 
I would imagine most discussions on this topic are referring to racing or HPDE. Most road cars are setup with a fair amount of understeer for good reasons. For the vast majority of drivers, under most road conditions, it is safest to keep it that way. Even a neutral handling car can become a handful in the hands of unskilled drivers not accustomed to driving at the threshold of tire traction. To tweak a street car's cornering attitude by changing its tire pressure in a significant manner, the driver either really knows what he's doing... or he's heading into impending disaster.


BTW, forgot to mention one other tidbit on how increasing tire pressure could affecting handling... As mentioned above, doing so tends to stiffen "tire spring" and reduce tire compliance. That is, a tire's ability to conform to the rough/uneven/undulating road surface and maintain traction. This is especially true for large heavy wheels and very low profile wide tires. During hard cornering, the outside rear tire could possibly lose contact with the road surface and break traction. Even if the break is momentary, this could result in SNAP OVERSTEER, which is very difficult to recover. This is another reason I run 18"s. It is also why I avoid super wide rear tires just for the looks.

This circles the discussion back to this thread's topic... while stiffer springs (either coil or anti-roll bar) can improve cornering by reduce the effect of lateral weight transfer, that is only a net positive if the road/track surfaces are smooth. Over rough road/track surfaces, too stiff a suspension can lead to insufficient suspension compliance. The result is the wheel/tires can have a tendency to hop off the road/track surface and break traction. The gummiest and widest tire in the world won't give you any grip, if it is hanging in the air.
Really love your posts on this subject, gives a good insight on handling.
I’m interested on your thoughts on my personal setup, whether its good or bad, I welcome your honest feedback.
Being in Australia I have the GT = US GT2 with active shocks with factory springs & I’m not lowered.
Set Up is:
Eibach Swaybars front & rear setting: both on soft
Whiteline HD Endlinks front & rear
Ultra Racing Chassis Braces: Centre & Rear only
19” Koya Wheels F: 8.5 & R: 9.5 each wheel is 4kg lighter than factory wheels:
Tyres: Falken FK510 F: 245/35/19 & R: 275/30/19.

Appreciate your input/comments.
 
Really love your posts on this subject, gives a good insight on handling.
I’m interested on your thoughts on my personal setup, whether its good or bad, I welcome your honest feedback.
Being in Australia I have the GT = US GT2 with active shocks with factory springs & I’m not lowered.
Set Up is:
Eibach Swaybars front & rear setting: both on soft
Whiteline HD Endlinks front & rear
Ultra Racing Chassis Braces: Centre & Rear only
19” Koya Wheels F: 8.5 & R: 9.5 each wheel is 4kg lighter than factory wheels:
Tyres: Falken FK510 F: 245/35/19 & R: 275/30/19.

Appreciate your input/comments.
It's not always fair for me to critique on others' suspension setup, because quite often folks have different goals than mine. So, I'll just address the things I see that are more pertinent to the topic of this thread.

1. Lighter wheels. 4 kg is quite substantial. I always say this should be the very first suspension upgrade for everybody still on OEM wheels. As long as the new wheels are properly spec'ed for the car's load rating, there is practically no downside to it - unlike just about everything you might do with suspension tuning, which almost always carries some negatives. With lighter wheels, you get less unsprung mass, so your suspension - even if it's bone stock - will be better able to control the movement of the now lighter wheels. This means better adhesion to the tarmac for better overall traction, especially over rougher pavement. It means faster reaction to bumps and less likelihood of bottoming out. Lower rotation inertia means faster accel/decel for better performance and mpg.

2. Anti-roll bars. You actually get the most bang for the buck with stock suspension. The reason is that once you start lowering the car and going to stiffer springs and dampers, your chassis will pitch and roll less, which is a good thing obviously. However, along with that comes less suspension articulation differences, under lateral acceleration and when hitting a bump. That means your anti-roll bars do less work overall. Not a bad thing, but nonetheless, your anti-roll bars do work a lot harder with full-travel long-stroke stock suspension. And yes, unless you have a specific reason(s) to do otherwise, leave the settings on soft. The stiffer you set the anti-roll bars, the less "independent" you suspension becomes. Imagine increasing your anti-roll bar's diameter larger and larger. At some point, you gonna end up with a solid axle. Difficult to argue that is a good thing.

More is only better when the gains reasonably justify the losses.

3. Adjustable end links. These are popular, but personally I've yet to see a convincing argument for street applications. Adjustables are typically only used on racing cars to fine-tune the end link lengths to compensate for corner weight differences, with the race driver on board. Along with corner balancing the car by adjusting ride height independently at all four wheels, this sets up the suspension to be as neutral as possible - again, with the race driver onboard. However, with a road car you daily, cargo and passenger loads could vary dramatically from day to day, trip to trip, so there is little reason to fine-tune for chassis neutrality when variables are multiple and unpredictable.

The other common justification for aftermarket end links is that OEM end links are weak and would bend. I don't buy this. All three of my Stingers/G70 are on OEM end links and all three have seen substantial track time and been pushed hard. I've found ZERO evidence of them bending/yielding under stress. If anybody else have solid evidence, I'm not beyond convincing. However, just showing a pic of a crooked OEM end link, which for all I know was probably chucked in a vise and whacked with a sledge hammer.... uh, nah.
 
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From interior to exterior to high performance - everything you need for your Stinger awaits you...
It's not always fair for me to critique on others' suspension setup, because quite often folks have different goals than mine. So, I'll just address the things I see that are more pertinent to the topic of this thread.

1. Lighter wheels. 4 kg is quite substantial. I always say this should the very first suspension upgrade for everybody still on OEM wheels. As long as the new wheels are properly spec'ed for the car's load rating, there is practically no downside to it - unlike just about everything you might do with suspension tuning, which almost always carries some negatives. With lighter wheels, you get less unsprung mass, so your suspension - even if it's bone stock - will be better able to control the movement of the now lighter wheels. This means better adhesion to the tarmac for better overall traction, especially over rougher pavement. It means faster reaction to bumps and less likelihood of bottoming out. Lower rotation inertia means faster accel/decel for better performance and mpg.

2. Anti-roll bars. You actually get the most bang for the buck with stock suspension. The reason is that once you start lowering the car and going to stiffer springs and dampers, your chassis will pitch and yaw less, which is a good thing obviously. However, along with that comes less suspension articulation differences, under lateral acceleration and when hitting a bump. That means your anti-roll bars do less work overall. Not a bad thing, but nonetheless, your anti-roll bars do work a lot harder with full-travel long-stroke stock suspension. And yes, unless you have a specific reason(s) to do otherwise, leave the settings on soft. The stiffer you set the anti-roll bars, the less "independent" you suspension become. Imagine increasing your anti-roll bar's diameter larger and larger. At some point, you gonna end up with a solid axle. Difficult to argue that is a good thing.

More is only better when the gains reasonably justify the losses.

3. Adjustable end links. These are popular, but personally I've yet to see a convincing argument for street applications. Adjustables are typically only used on racing cars to fine-tune the end link lengths to compensate for corner weight differences, with the race driver on board. Along with corner balancing the car by adjusting ride height independently at all four wheels, this sets up the suspension to be as neutral as possible - again, with the race driver onboard. However, with a road car you daily, cargo and passenger loads could vary dramatically from day to day, trip to trip, so there is little reason to fine-tune for chassis neutrality when variables are multiple and unpredictable.

The other common justification for aftermarket end links is that OEM end links are weak and would bend. I don't buy this. All three of my Stingers/G70 are on OEM end links and all three have seen substantial track time and been pushed hard. I've found ZERO evidence of them bending/yielding under stress. If anybody else have solid evidence, I'm not beyond convincing. However, just showing a pic of an OEM end link, which for all I know was probably chucked in a vise and whacked with a sledge hammer.... uh, nah.
Thank you for your comments, they are very insightful.
 
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3. Adjustable end links. These are popular, but personally I've yet to see a convincing argument for street applications. Adjustables are typically only used on racing cars to fine-tune the end link lengths to compensate for corner weight differences, with the race driver on board. Along with corner balancing the car by adjusting ride height independently at all four wheels, this sets up the suspension to be as neutral as possible - again, with the race driver onboard. However, with a road car you daily, cargo and passenger loads could vary dramatically from day to day, trip to trip, so there is little reason to fine-tune for chassis neutrality when variables are multiple and unpredictable.

The other common justification for aftermarket end links is that OEM end links are weak and would bend. I don't buy this. All three of my Stingers/G70 are on OEM end links and all three have seen substantial track time and been pushed hard. I've found ZERO evidence of them bending/yielding under stress. If anybody else have solid evidence, I'm not beyond convincing. However, just showing a pic of a crooked OEM end link, which for all I know was probably chucked in a vise and whacked with a sledge hammer.... uh, nah.
Pardon my ignorance here, but I heard that if you want to lower your Stinger/G70, that you'd want to get shorter or adjustable end links.

Granted, I'm not planning on lowering her and would get different end links when the stock ones cease to work--if they ever do, but wanted your take on the matter for the good of general knowledge.
 
I heard that if you want to lower your Stinger/G70, that you'd want to get shorter or adjustable end links.
Nope. That's a common misconception. Just about all aftermarket application-specific anti-roll bars are made to be direct drop in compatible, with attachment points that are identical to stock anti-roll bars. Think about where the end links of the anti-roll bars are attached to. They are always somewhere that is fixed relative to the wheel center. Regardless of how much you lower the car, that point does not change. As the suspension articulates, that attachment point does move up/down and prescribe an "arc" relative to the anti-roll bar bushing. The path of that "arc" does not change... nor should it. OEM engineers did their homework to make sure that "arc" allows the suspension articulation to actuate the anti-roll bar (to exert torsion) in the most linear manner through out the arc travel. By lowering the car, all you do is reduce the length of the "arc", by truncating the lower portion of it.

If you change the end link attachment point, you are changing that "arc" and the geometry of the lever arm with which the anti-roll bar is actuated by the suspension articulation. Not to say someone couldn't figure out how to improve on the stock linearity curve, especially at the extreme end of the articulation. Suffice it to say, you'd better know what you are doing. Most casual street modders who do mess with adjustable end links, dare I say... don't.

Now, as I mentioned above, for those racers who chase lap times in 10ths of seconds, adjustable end links might make sense. Even then, when they do this for corner balancing, they most often adjust one side ONLY, to a point where the ant-roll bar is neutral (no load on torsion spring exerted) with race driver's weight. Really only one adjustable end link is necessary to do this, but for convenience sake, they are sold in pairs and installed on both ends, so the typically very small tweak necessary can be done on either end.

If you want to get really anal about this and follow this same racing paradigm tweaking to compensate (only) for driver's weight... sure, knock yourself out. At least you are doing it with proper reasoning. Whether it's overkill for a daily driver... that I leave to you to decide.
 
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