RWD w/LSD stock suspension: oversteer or understeer?

[Beege]

Hey ladies and gents,

Looking for some opinions. Does your RWD 3.3 with LSD oversteer or understeer?

So here's what's in my head. The goal of sway bars is to get it as neutral as possible. That's my goal anyway. Not trying to be a drift king.

So with that said, I'm thinking upgrading both sway bars aren't necessary. If the car oversteers, you stiffen the front to get it closer to neutral right? If it understeers, you stiffen the back to get it to neutral right?

If changing one of those brings it close to neutral, is that good enough?

What if changing both brings it to neutral, is that overall better because it's stiffer all around?

 

[Dennis]

Changing both will make it loose its liveliness to direction change. This car steers and turns very well. Stiffening either will loose this balance and stiffening both have a cancelling effect. Your preference can be tweak by stiffening either front or rear but the balance maybe compromise. Unless you are planning to track it. Do take note the shocks will need to be tweak to compensate for the changes too.

 

[Helo58]

Typically, manufacturers build in understeer from the factory. This allows your car to plow off of the road rather than into oncoming traffic should you get a little overly spirited and lose control. It would be my guess that this car is no different, with the exception of power oversteer. I have the RWD with LSD and I haven't really "hooned" it yet because I just don't think the car is up to it in standard form.

 

[Stinger GT SS]

I haven’t noticed either way, it steers very well under hard acceleration & cornering, only the rear can sometimes get a bit twitchy, but I like that anyway, opposite lock controls that.

 

[Dennis]

Yes the slight twitch only happens when you put the power down at fast cornering speed. It actually creates some thrills in it.

Most reviewers mention its tail happy maybe overblown as most higher horsepower cars with full torque coming in so low down will naturally introduce this. That happens to most high performance models. If driven at sensible limits its actually pretty accurate and satisfying. IMHO.

It maybe amplified because its coming from KIA!

 

[Dochidalgo]

Changing both will make it loose its liveliness to direction change. This car steers and turns very well. Stiffening either will loose this balance and stiffening both have a cancelling effect. Your preference can be tweak by stiffening either front or rear but the balance maybe compromise. Unless you are planning to track it. Do take note the shocks will need to be tweak to compensate for the changes too.

Typically, manufacturers build in understeer from the factory. This allows your car to plow off of the road rather than into oncoming traffic should you get a little overly spirited and lose control. It would be my guess that this car is no different, with the exception of power oversteer. I have the RWD with LSD (Limited Slip Differential) and I haven't really "hooned" it yet because I just don't think the car is up to it in standard form.

Wow, I've learning some new about suspension regarding sway bars.......
So, I will not "upgrade" the sway bars....progresive springs only.
Thanks teachers !!!!

 

[Beege]

Let's say the stock bars are balanced and the car is neutral.

Now let's say upgrading the front and rear bars are also balanced and the car is neutral.

Is there a positive affect on having the upgraded stiffer bars on compared to the stock even though both setups are neutral?

 

[Dennis]

Let's say the stock bars are balanced and the car is neutral.

Now let's say upgrading the front and rear bars are also balanced and the car is neutral.

Is there a positive affect on having the upgraded stiffer bars on compared to the stock even though both setups are neutral?

Yes if the anti toll bars are upgraded in the same ratio front and rear the car will have a higher limit but as I mention earlier the shocks and spring rates will need to be change to accommodate the increase respond and rigidity from the anti roll bar.

If in terms of absolute stiffness in turns with just anti roll bar replacement yes it can be felt but the shocks will need to be realve to have a balance in terms of comfort and safety which was initially engineered by the manufacturer for "real"world usage. Valving and fluid in shocks have great impact for damping control not forgetting spring rate for rebound .

 

[Helo58]

Let's say the stock bars are balanced and the car is neutral. Now let's say upgrading the front and rear bars are also balanced and the car is neutral. Is there a positive affect on having the upgraded stiffer bars on compared to the stock even though both setups are neutral?

Getting the optimum performance from your suspension really is determined by your ultimate goal (comfort, drifting, autocross, road course, drag-strip, etc.). As I understand it, you have shocks, springs, ARBs, and the geometry of the hard points where everything connects. Any change in one of these areas will affect the system as a whole. This means choosing the appropriate rate(s) for your springs, shocks, and ARBs to work together. If you alter only one component of the system, it is entirely possible that you hurt the overall performance of your car rather than help it. It really all depends on how you plan to use the car.

 

[eflyguy]

There is no one best setup for a daily driver that will be optimal in all circumstances.

Even setting up for a track, you would take the track itself into account. A vehicle might benefit from different settings and even different driver styles at each track. You might find oversteer as you apply power to limit your speed in certain corners, say, coming over a rise, but in other corners, or at other tracks, you might be diving into a sharp corner and can leverage the shift in weight to provide more grip, and get on the power sooner.

Suspension is a very complicated system that can be tuned for optimal results. Even at the highest levels of racing, some minor adjustments to help change the balance are made mid-race, perhaps depending on tire condition. Brake bias, even, is often adjustable in the cockpit, and is required to be adjusted constantly for certain parts of the track.

So improving overall handling on a vehicle like the Stinger is going to be a compromise - it already is from the factory, but it's a well-executed compromise requiring little (if any) changes to satisfy most drivers. That's kind of the point - they got it right out of the factory.

Put another way:

Getting the optimum performance from your suspension really is determined by your ultimate goal (comfort, drifting, autocross, road course, drag-strip, etc.). .... If you alter only one component of the system, it is entirely possible that you hurt the overall performance of your car rather than help it. It really all depends on how you plan to use the car.

 

[Mr Skillet]

Finally a geeky handling balance discussion! ....

So here's my opinion on it, I've not pushed the car extremely hard, but I have throw it around a few cloverleaf freeway ramps as well as a few windy foothill roads. My experience is limited to HPDE track days, autox, karting, Canyons ( 95 240sx/ 91 nsx )

My take is that the car actually has pretty good lateral rigidity and pretty responsive chassis considering its GT roots and a 4000 Lb curb weight. Overall, I feel like on the street the car points (changes directions very well) which is indicative of quick steering, stiff chassis and good overall suspension tuning.

Increasing the roll stiffness by adding bars will result in less roll, but less roll doesn't necessarily translate to better handling. Stiffer suspension also increase tire loading (transfers weight faster). So at the limits of grip, you may run into understeer and oversteer more quickly as you approach the limit.

Initial impressions of the handling balance, I'd say the car turns in quick, transitions to a moderate (safe) amount of understeer mid corner under steady state cornering, then, under power for RWD/LSD models the car wants to rotate progressively. I feel like this is pretty ideal for a street car, especially one that can put 360lbs of torque to the rear wheels.

On the subject of springs/shocks, I feel like this car is under sprung and over damped, which makes for a super comfy ride over broken pavement, but feels a little floaty, esp in the rear over larger bumps at fwy speeds. I know people have reported great results with Eibach springs and bars, I wonder if anyone on this forum has done just the springs without the bars. I'd love to drive a v6 gt2 with only springs to sample the ride as well as the changes to handling balance. Also because of this design priority, I think moderate increases in spring stiffness sway bar and springs shouldn't be an issue, at least from the point of the dampers not being able to keep up with keeping the stiffer springs in check.

Added benefit to the softer suspension is that weight transfer actually happens more slowly (weight transfer is not the same as body movement, i.e. roll, squat, dive) The slower weight transfer gives you a much more forgiving limit handling and covers up driver mistakes well, either ham fisted steering or abrupt throttle/brake inputs. This is one of the reason the FRS/MX-5 and a few other amazing drivers cars actually come with fairly soft suspension tuning.

 

[Dochidalgo]

My former 2016 Nissan Maxima SR had a good balance between confort and performance with a stiffier suspensión than my Stinger GT2.
I like to drive fast (in spite of my age) with my trust in take highway curves with confidence, but my Stinger has fail in this departament.
So, I am going to replace the stock springs with the Eibach pro Kit first and prove how the suspensión behave.

 

[eflyguy]

I'm kind of shocked to read that BUT every driver is different and prefers a certain feel. I've only test-driven the stinger a couple of times and in those brief times I was very pleased with the "feel" of the car in those situations. After living with one for a while, perhaps I'll think differently.

After I posted earlier, I was thinking - wouldn't it be nice if we could switch the suspension between comfort and sport for each axle? Stiffen the rear only, for example, for more oversteer...

 

[Mr Skillet]

I haven’t noticed either way, it steers very well under hard acceleration & cornering, only the rear can sometimes get a bit twitchy, but I like that anyway, opposite lock controls that.

I've noticed that it can be twitchy because of the power delivery and how the torque comes on hard when you're out of boost and put your foot down, especially in sport mode. If you're in boost and feed in throttle, the car rotates nicely on throttle without needing much opposite lock at all. Even when it breaks loose, the car steps out very progressively, I really like this aspect of the handling, it really is a well sorted out RWD setup. On turn in, I've also noticed that the car actually allows small angles of rotation if you trail brake instead of plowing at corner entry while turning like most long wheel base heavy sedans do. The balance of the car kinda reminds me of the e39 m5

 

[Stinger GT SS]

I've noticed that it can be twitchy because of the power delivery and how the torque comes on hard when you're out of boost and put your foot down, especially in sport mode. If you're in boost and feed in throttle, the car rotates nicely on throttle without needing much opposite lock at all. Even when it breaks loose, the car steps out very progressively, I really like this aspect of the handling, it really is a well sorted out RWD setup. On turn in, I've also noticed that the car actually allows small angles of rotation if you trail brake instead of plowing at corner entry while turning like most long wheel base heavy sedans do. The balance of the car kinda reminds me of the e39 m5

Yes totally agree with your analysis, your comments nail it for me.