Sway bars - why do so many people recommend stiff front, loose rear?

[DAYTA]

Regarding adjustable sway bar settings, I notice that the majority of recommendations on here are to have the front bar at full stiff and the rear bar (if any) at full loose. I'm not a suspension guru, but based on what I've read and personal limited experience, I would think that would introduce a ton of understeer. Ultimately, it sounds like a safe setup but would also kill the fun.


To give you a bit of a background of my current suspension/chassis setup. The list below is also in order of when the parts were installed, the LoveFab chassis brace being the last thing added:

- KW V3
- GT-Spec front lower chassis brace
- NSX-R front frame stabilizer bar
- LoveFab rear targa brace
- SOS swaybars (front & rear)
- LoveFab front upper chassis brace

For my setup, I chose to keep things balance (mid stiff front and rear). Prior to adding the last LoveFab front brace, those settings made the car handle beautifully neutral. However, after adding the last brace, I noticed that initial turn-in and understeer are both noticeably worse.

Ideally, I don't want to remove the LoveFab upper chassis brace because, aside from the unexpected negative side effects, it actually does greatly improve rigidity on my targa. Steering vibration at higher speeds and cowl shake are significantly reduced and the car just feels much more solid. That said, I also miss how the car handled before the brace so after winter is over, I intend to try and dial out the turn-in and understeer.

To do that, I was thinking about adjusting two things:

1) Loosening up the front sway bar to its loosest setting
2) Adjust my alignment specs to increase toe-out (currently at +0.10 degrees L+R, +0.20 degrees total)

Are these bad or dangerous ideas? Could the LoveFab front chassis brace be making my car TOO stiff to the point that there isn't enough load on the outer tire in corners and I'm actually losing grip as a result?

 

[stuntman]

Stiffening the bar reduces roll and INCREASES load on the outside wheel.

What tires, size, camber, pressures, etc... Are you running?

 

[DAYTA]

Stiffening the bar reduces roll and INCREASES load on the outside wheel.

What tires, size, camber, pressures, etc... Are you running?

I'm running AD08Rs all around in OEM sizes (215/40/17 front, 255/40/17 rear) @ 34psi all around. Front tires are new, rear tires will be replaced this coming season. My car is lowered about 2" so my rear camber is more than I'd like (-1.5F, -3.0R).

I will defer to your knowledge as I know you're well-versed but i would think that stiffening the bar would keep the inner wheel more planted in a corner and thus split the load more evenly rather than apply greater force to the outer wheel.

I would think I'd want to split the load more evenly to gain more front end grip, so regardless of the physics it sounds like loosening the front sway bar would yield my desired result?

 

[stuntman]

Its a common misunderstanding to confuse body roll with weight transfer. By increasing your roll stiffness (reducing roll from a larger swaybar), the body rolls less and transfers more weight across the tire, thus loading the outside tire more. I understand how the lack of roll could be perceived as having more weight in the inside tire but in reality, the inside tire becomes unloaded the stiffer your swaybar is. This is the reason why stiffening the swaybar reduces roll and reduces grip on that end of the car, because the inside tire is doing less work and the outside tire becomes loaded more and reaches its limit sooner.

What are your spring rates and what suspension are you running? I typically don't like very much rear swaybar (run full soft or the stock zanardi rear) on the NSX, and the NSX needs a pretty stiff front bar to control roll due to its low geometric roll center. I would try going to a track day and work on trailbraking. Your understeer could be wrong driver inputs making the car understeer and you don't want to tune your car out in left field to oversteer really bad when you give it the inputs to oversteer.

0.02

 

[iLiftSystems]

A stiff front bar will give the car a more responsive turn in that is noticeable during normal street driving without having to increase the spring rates.

Another benefit of using a stiff front bar is that under compression when driving over a steep driveway at an angle, the bar will transfer some of the load from the heavily compressed spring to the spring on the opposite side of the car. This is a benefit to those who want to run their car as low as possible without tire hitting the fender and without having to resort to overly stiff front springs.

My car has over sized tires (235/40 and 295/35) that would rub the fenders if the tires travel up that high. A stiff front bar helps to limit the suspension travel at the heavily loaded side and provides some of the benefits of having stiffer springs without the constant harshness of using stiffer springs.

 

[DAYTA]

Its a common misunderstanding to confuse body roll with weight transfer. By increasing your roll stiffness (reducing roll from a larger swaybar), the body rolls less and transfers more weight across the tire, thus loading the outside tire more. I understand how the lack of roll could be perceived as having more weight in the inside tire but in reality, the inside tire becomes unloaded the stiffer your swaybar is. This is the reason why stiffening the swaybar reduces roll and reduces grip on that end of the car, because the inside tire is doing less work and the outside tire becomes loaded more and reaches its limit sooner.

What are your spring rates and what suspension are you running? I typically don't like very much rear swaybar (run full soft or the stock zanardi rear) on the NSX, and the NSX needs a pretty stiff front bar to control roll due to its low geometric roll center. I would try going to a track day and work on trailbraking. Your understeer could be wrong driver inputs making the car understeer and you don't want to tune your car out in left field to oversteer really bad when you give it the inputs to oversteer.

0.02

I'm running KW V3s with the stock springs (350 lbs/in F&R). Lowered 2" all around.

I think I figured out my misunderstanding. With a stiffer bar, the suspension travel for each side is less independent of one another. That means if more weight is applied to one side when loading into a corner, less is applied to the other side since they are inversely linked as a result of the added stiffness. Similar to a solid rear axle on a Mustang, right?

Per your explanation of "stiffening the swaybar reduces roll and reduces grip on that end of the car", why would that be a good thing? Wouldn't you want to have more grip on the inside tire (and thus overall)? With all of the added chassis bracing, my car has ZERO body roll but I think maybe it should have a little to improve overall front grip.

A stiff front bar will give the car a more responsive turn in that is noticeable during normal street driving without having to increase the spring rates.

Coincidentally, I'm finding the exact opposite is true. I have noticeably worse turn-in after adding that last chassis brace. Ultimately, this is what I've noticed even more than the increased understeer - the car just seems less willing to turn into a corner which I don't like.

To improve turn-in, would the stiffness settings on my swaybars have a significant impact or should I be more focused on adjusting my alignment specs (currently at +0.10 degrees toe out FL and FR, +0.20 total toe). Also what are the OEM specs for front toe converted into degrees? I'm thinking I have fairly conservative toe settings as is.

 

[Hapa88]

Coincidentally, I'm finding the exact opposite is true. I have noticeably worse turn-in after adding that last chassis brace. Ultimately, this is what I've noticed even more than the increased understeer - the car just seems less willing to turn into a corner which I don't like.

Keep in mind you two are talking about two different bars. iLift is talking about stiffing a "sway bar" and you're talking about stiffing a "chassis brace". Don't confuse the purpose and effects of the two.

 

[DAYTA]

Keep in mind you two are talking about two different bars. iLift is talking about stiffing a "sway bar" and you're talking about stiffing a "chassis brace". Don't confuse the purpose and effects of the two.

Well yes and no. My thread is asking for opinions on whether I can correct the negative side effects of adding a chassis brace by adjusting the stiffness of my sway bar.

 

[stuntman]

I'm running KW V3s with the stock springs (350 lbs/in F&R). Lowered 2" all around.

I think I figured out my misunderstanding. With a stiffer bar, the suspension travel for each side is less independent of one another. That means if more weight is applied to one side when loading into a corner, less is applied to the other side since they are inversely linked as a result of the added stiffness. Similar to a solid rear axle on a Mustang, right?

Per your explanation of "stiffening the swaybar reduces roll and reduces grip on that end of the car", why would that be a good thing? Wouldn't you want to have more grip on the inside tire (and thus overall)? With all of the added chassis bracing, my car has ZERO body roll but I think maybe it should have a little to improve overall front grip.

Coincidentally, I'm finding the exact opposite is true. I have noticeably worse turn-in after adding that last chassis brace. Ultimately, this is what I've noticed even more than the increased understeer - the car just seems less willing to turn into a corner which I don't like.

To improve turn-in, would the stiffness settings on my swaybars have a significant impact or should I be more focused on adjusting my alignment specs (currently at +0.10 degrees toe out FL and FR, +0.20 total toe). Also what are the OEM specs for front toe converted into degrees? I'm thinking I have fairly conservative toe settings as is.

You're still misunderstanding how a swaybar works. When a car rolls, it compresses the outside tire and twists the swaybar arm. Since the swaybar is shaped like a "U", the swaybar arm on the inside tire tries to compress the inside suspension -which reduces body roll and 'lifts' the inside tire off the ground -thus unloading the inside tire.

*Stiffening a swaybar reduces body roll by INCREASING weight transfer across a pair of tires and UNLOADING the INSIDE tire more.

What are your compression and rebound settings set at and what is your ride height? (Measure the distance from the ground to the bottom of the jack tabs on your framerail. Your car has 3 jack tabs along the framerail, just measure the distance from the ground to the center of the jack tabs for the front and rear tabs).

I still think you should try going to an autocross or track day and work on your driving and especially trailbraking -which will greatly reduce any turn-in and entry understeer problems.

 

[darock]

What's also often overlooked is the fact that a stiff sway bar will at one point prevent the suspension from moving independent. That not only massively reduces riding comfort, it also reduces mechanical grip because a street is not a perfectly even surface.

I am not a friend of stiff sway bars. Body roll should be controlled by the correct spring rate, not by adding the biggest sway bars available.

Bernhard

 

[RYU]

No fun being killed in my setup.

I'm on a heavy front bar and light rear bar. My springs are also heavier in the front than the rear. I've never been faster. I even dropped 3 secs from my PB last wknd. (part of that were the tires but most was the confidence inspiring stability). .OH YEA! The biggest part was following iLLWillem around the track. So effectively.. i cheated.

I can induce understeer thru throttle inputs which is great. I'm still learning where the limits of the rear are in this new setup. There's a lot of grip back there i'm not use to. My car use to fun and loose but it wasn't very fast in retrospect. Now its a different kind of fun. I like it. Good dampers are worth their weight in gold.

 

[liftnot]

Springs are for damping. Roll should be controlled by ARB.

http://www.nsxprime.com/wiki/Suspension

[h=2]How Should Roll Stiffness Be Improved?[/h][AWN] Ideally, you want to limit roll with anti-roll bars. While it's true that a car's roll resistance can come from either the springs or the bars, increasing the spring rate to limit roll isn't such a good idea. Here's why:
Let's say that you can live with a HUGE amount of roll... Like 10 degrees or so. How far does the outboard spring compress when the chassis rolls that much? An inch, maybe? I have no idea how stiff the stock springs are, exactly, but for the sake of argument, let's say that they're 150-pound-per-inch springs (they probably have a lower rate, but I'll give them the benefit of the doubt).
Ok... This means that, at 10 degrees of roll (which compresses the spring an inch), each outboard spring is only contributing 150 pounds of roll resistance to the chassis. Your car wants a whole lot more than 150 pounds of roll-resistance at each axle, especially if you want to limit roll to a more-reasonable value, like 5 degrees or less. To get your desired roll-resistance numbers from the springs alone, your springs will be so stiff that the tires will hardly spend any time on the ground; every little bump on the track will send them into the air.
If, on the other hand, you put relatively soft springs on the car and use a stiff sway bar, you'll get good tire compliance AND good roll resistance. You'll also be able to quickly adjust the car's over/understeer balance, since it's a whole lot easier to move a swaybar droplink (or even to replace the bar) than to replace springs.
In general, it's best NOT to use one suspension component (the springs, in this case) to perform multiple tasks... If you can split the suspension control among multiple components (springs for keeping the car off the ground, sway bars for limiting roll), you don't have to compromise one aspect of the car's handling for another. Well... You don't have to compromise MUCH, anyway.

 

[stuntman]

What's also often overlooked is the fact that a stiff sway bar will at one point prevent the suspension from moving independent. That not only massively reduces riding comfort, it also reduces mechanical grip because a street is not a perfectly even surface.

I am not a friend of stiff sway bars. Body roll should be controlled by the correct spring rate, not by adding the biggest sway bars available.

Bernhard

The concern for losing 'independence' is often blown way out of proportion. While there may be a slight loss of ride quality, it is very minimal from a street (and especially track) perspective. It is far better to control/reduce body roll with swaybars than it is with stiffer springs.

 

[99problems]

What's also often overlooked is the fact that a stiff sway bar will at one point prevent the suspension from moving independent. That not only massively reduces riding comfort, it also reduces mechanical grip because a street is not a perfectly even surface.

I am not a friend of stiff sway bars. Body roll should be controlled by the correct spring rate, not by adding the biggest sway bars available.

Bernhard

I actually like the unison feeling.
Maybe it's my 21 year old back.
*Shrug*

 

[DAYTA]

You're still misunderstanding how a swaybar works. When a car rolls, it compresses the outside tire and twists the swaybar arm. Since the swaybar is shaped like a "U", the swaybar arm on the inside tire tries to compress the inside suspension -which reduces body roll and 'lifts' the inside tire off the ground -thus unloading the inside tire.

*Stiffening a swaybar reduces body roll by INCREASING weight transfer across a pair of tires and UNLOADING the INSIDE tire more.

What are your compression and rebound settings set at and what is your ride height? (Measure the distance from the ground to the bottom of the jack tabs on your framerail. Your car has 3 jack tabs along the framerail, just measure the distance from the ground to the center of the jack tabs for the front and rear tabs).

I still think you should try going to an autocross or track day and work on your driving and especially trailbraking -which will greatly reduce any turn-in and entry understeer problems.

I guess my response didn't specify outer vs inner weight transfer, but I believe I do understand the physics of how a swaybar controls body roll. I also have been to a few track days (not in the NSX though) and done two Skip Barber advanced driving schools at Lime Rock so I do have a little experience.

My initial concern is around the fact that my car felt sharper and quicker (specifically turn-in) before adding the last chassis brace. I won't track or autox the NSX so I will never push the car hard enough that trailbraking and other advanced driving techniques will make a difference. I just want to see if it's possible to adjust my car so that it responds the way it did before.

It's been a torrential downpour here today so I haven't had a chance to measure my ride height yet. I will try to do it tomorrow. Compression and rebound are both set dead in the middle to KW specs.

Also, can someone convert factory front toe out settings into degrees? Are my settings too conservative (+0.10 degrees F+R< +0.20 total degrees).

 

[docjohn]

No fun being killed in my setup.

I'm on a heavy front bar and light rear bar. My springs are also heavier in the front than the rear. I've never been faster. I even dropped 3 secs from my PB last wknd. (part of that were the tires but most was the confidence inspiring stability). .OH YEA! The biggest part was following iLLWillem around the track. So effectively.. i cheated.

I can induce understeer thru throttle inputs which is great. I'm still learning where the limits of the rear are in this new setup. There's a lot of grip back there i'm not use to. My car use to fun and loose but it wasn't very fast in retrospect. Now its a different kind of fun. I like it. Good dampers are worth their weight in gold.

View attachment 119864

View attachment 119865

good for you....btw at least you understand what Billy has been repeating over and over on prime.....in a mid engine car you really want to maximize rear end grip because you have enough control of front weight transfer with your feet...I have been on track with some very fast cars with lots of mechanical grip in corners with soft springs,good dampers and big bars.

 

[stuntman]

I guess my response didn't specify outer vs inner weight transfer, but I believe I do understand the physics of how a swaybar controls body roll. I also have been to a few track days (not in the NSX though) and done two Skip Barber advanced driving schools at Lime Rock so I do have a little experience.

My initial concern is around the fact that my car felt sharper and quicker (specifically turn-in) before adding the last chassis brace. I won't track or autox the NSX so I will never push the car hard enough that trailbraking and other advanced driving techniques will make a difference. I just want to see if it's possible to adjust my car so that it responds the way it did before.

It's been a torrential downpour here today so I haven't had a chance to measure my ride height yet. I will try to do it tomorrow. Compression and rebound are both set dead in the middle to KW specs.

Also, can someone convert factory front toe out settings into degrees? Are my settings too conservative (+0.10 degrees F+R< +0.20 total degrees).

Your camber seems to be okay, let me know what your ride heights are set at. As far as shock settings go, I think you are probably too soft on your compression (bottom adjuster). Try the recommended settins in Posts #10 & 18:

http://www.nsxprime.com/forum/showt...Spring-Packages-by-FX-Motorsports-Development


Other than dialing in your dampers, rake, and toe; it does not appear your settings are out in left field. It's important to have a neutral handling setup. The NSX is a very good chassis and in stock form (and in an ideal modified form) the car should turn better and oversteer with proper inputs (trailbraking) and understeer with proper inputs (on throttle). You don't want your car to be too neutral or oversteering when you're on the throttle because if you then try trailbraking intentionally or accidentally if you enter a corner too fast, your car could rotate too quickly/snap oversteer.

 

[DAYTA]

Your camber seems to be okay, let me know what your ride heights are set at. As far as shock settings go, I think you are probably too soft on your compression (bottom adjuster). Try the recommended settins in Posts #10 & 18:

http://www.nsxprime.com/forum/showt...Spring-Packages-by-FX-Motorsports-Development


Other than dialing in your dampers, rake, and toe; it does not appear your settings are out in left field. It's important to have a neutral handling setup. The NSX is a very good chassis and in stock form (and in an ideal modified form) the car should turn better and oversteer with proper inputs (trailbraking) and understeer with proper inputs (on throttle). You don't want your car to be too neutral or oversteering when you're on the throttle because if you then try trailbraking intentionally or accidentally if you enter a corner too fast, your car could rotate too quickly/snap oversteer.

Just measured my ride height:

Front: 4.0" clearance (L+R)
Rear: 4.5" clearance (L+R)

I like the rake I currently run from an aesthetic perspective, but I'm not sure what is ideal for performance. I will also look into changing the compression settings when the car comes out of hibernation in the next few months.

What front toe settings are typically ideal for optimal turn-in response on a street-driven car without destroying the tires?

 

[stuntman]

So you measured from the ground to the bottom of the front jack point (in the center of the jack tab), and from the ground to the bottom of the rear jack point (in the center of the jack tab)? Do you have a side profile pic of your car?

A ballpark rake is 0-0.5". So you're on the high end of that range which mean your car 'should' turn better on entry and off-throttle. I still don't see anything that points toward understeer.

Slight toe-in (2-3mm total) would typically improve your initial turn-in response. Slight toe-out (2-3mm total) will typically deaden the inital response but give you more mid-corner and corner exit front grip.

 

[jmarksnsx]

Billy do you recommend the Type R front bar in combo with the KW V3 suspension?

 

[stuntman]

At a minimum, I would go with the R front bar bit preferably something larger, especially if you track your car or drive spiritedly. My car rolls too much and has too much entry, trailbrake oversteer with the stock front bar. Pole2Flag makes one of the best looking bars for the NSX and I will be testing it soon.

 

[DAYTA]

So you measured from the ground to the bottom of the front jack point (in the center of the jack tab), and from the ground to the bottom of the rear jack point (in the center of the jack tab)? Do you have a side profile pic of your car?

A ballpark rake is 0-0.5". So you're on the high end of that range which mean your car 'should' turn better on entry and off-throttle. I still don't see anything that points toward understeer.

Slight toe-in (2-3mm total) would typically improve your initial turn-in response. Slight toe-out (2-3mm total) will typically deaden the inital response but give you more mid-corner and corner exit front grip.

I don't have a good side profile pic of how the car sits currently. My measurements were from the ground to the bottom of the jack tabs (not middle) - figure add another 0.5" from bottom to middle. I haven't had any problems with it so far, but is that not ideal?

Interesting info about toe-in. Based on what I've read, I thought toe-out would improve initial turn-in response and toe-in would improve high speed stability. If toe-in is the correct approach to improving turn-in, are there any NSX guys running front toe-in settings? I've only seen guys running toe-out settings.

Also, for point of reference the public backroads I drive on are fairly tight and technical (usually entering corners at no more than 35-40MPH), so improving initial turn-in response is paramount.

- - - Updated - - -

Any thoughts on this discussion?

Toe out for turn in

 

[stuntman]

What kind of public backroads have 35-40mph corners? that is extremely slow. I don't know of many mountain roads that have extensive corners that are that tight, even the Tail of the Dragon has mostly 40+mph corners.

From this thread:

http://www.nsxprime.com/forum/showthread.php/185560-Alignment-setup-na1

It's difficult to talk about suspension through the internet because there are so many different factors that can affect the end result: toe, camber, caster, ackermann, scrub radius, tire pressure, tire construction, spring rates, roll center heights, dampers, etc... The suspension as a whole is a complicated system that works as a complete unit and any change to one aspect usually affects the others.

But getting back to toe: I agree Old Guy that toe-IN can improve straight line stability compared to toe-OUT which can follow the road imperfections. However, consider that tires do not generate lateral forces (grip) until the tire twists and deflects with a certain amount of slip angle. Since the outside loaded tire does most of the work in changing the direction of the car, toe-OUT has the outer tire pointing in the opposite direction of the turn.

Let's say there is 1 degrees of toe out per side. The outer tire needs to turn 1 degree just to be pointed straight, which does not contribute to lateral load generation. While the inner tire is now at 2 degrees, its contribution to directional change becomes ever less significant as weight is being transferred off of it and to the outer tire. As the outer tire gets increased load and builds up to 2,3,4...7,8,9 degrees of slip angle, it generates more and more lateral load.

For toe-IN. Lets say both tires have 1* of toe-IN. In this case the outer tire has 1* pre-loaded in the direction of a turn. As the car steers 1* into the corner, the outer tire increases to 2* of slip angle and deflection as load is being transferred to it, while the unloaded inner tire is now at 0*. At this stage, the toe-IN example has 2* of steering input from the outer LOADED tire and 0* on the unloaded inner tire (compared to the toe-OUT example where the outer, loaded tire is at 0* and the inner unloaded tire has 2*). The ideal, peak slip angle of, say 10*, for a tire gets there quicker in the toe-IN example.

So, why not always run toe-IN?

Depending on many of the other factors in the suspension, the improved turn-in response and 'pointy', 'direct', 'twitchy' feeling of toe-IN may not be desirable. Also the effects of toe can vary with speed and as said in my previous post, toe-OUT can contribute to more front grip steady-state than toe-IN. Also the improved turn-IN response of toe-IN becomes more significant at higher speeds, but also builds up to the steady-state understeer quicker.

For autocross, toe-IN would probably not be good, while at a track with high speed esses and transitions where the car needs to change direction quickly but settle to a (relative) steady-state understeer, toe-IN might be more desirable. It all depends on many factors and its difficult to give blanket statements for anything due to all of the variables in the suspension system. However, if a car oversteers at the limit but feels lazy from initial turning response, toe-IN might be a good direction to try. That or stiffening the dampers, front swaybar, or various other changes...

darock - where do you notice this 'floaty' feeling? Does it get worse the faster you go? Is it bad when going down a straight road, bumpy road, or when initially turning in corners?

 

[DAYTA]

I'm confident that guys who drive around my area (Fairfield and Westchester county) can attest to the fact that a large number of our backroads are driven at an average of 40MPH at most. Where I drive, the best backroads are exceptionally narrow with major elevation changes, dense wooded areas (i.e. blind corners), and no shoulders. The speed limit around some of my favorite roads in CT are as low as 25MPH, so it might sound slow but believe me 35-40MPH is the fastest I will go while still feeling safe and in control.

Below is one of my favorite driving roads in Greenwich, CT. Take a look at the street view to get an idea of what I mean.

https://www.google.com/maps/place/L...2!3m1!1s0x89c2a330672dec85:0x89b2e4ec587f76ad

I appreciate your explanation, but I've tried 3 different alignment settings on the NSX and my experiences seem to be more in line with the idea that toe-out (not toe-in) improves turn-in response. I also googled "toe in vs toe out turn-in response" and I'm confused as every other article/opinion I've read about toe settings and turn-in response contradicts your opinion. I can't speak to their validity but other discussions mention that "yaw moment" also needs to be factored in?

Below is a quote from another the discussion I linked earlier.

By "better" in this case most people mean "more responsive", i.e. more yaw moment for a given amount of steering angle. On a "twitchy" car "better" might be considered less responsive, but that's by the by.

So I made a very simple little excel spreadsheet calculating yaw moments against slip angle, and low and behold the answer came back that adding toe-out does improve the yaw moment for a given steering input... however I will caveat that slightly by saying it is heavily influenced by the slip angle vs. side thrust curve for the tyre.

Explanation below:-

For a simple model lets assume that the thrust generated by the tyre is proportional to the slip angle, so 1 degree equals say 10 units of force thrust, and 2 degrees equals 20 units of force thrust. Looking at some tyre curves this is approximately true at low slip angles, so is a fairly good assumption here. Also I've assumed that the vertical load on the tyres is equal at all times (not that accurate, but lets assume we have a really low c.g)

case 1: If both front tyres point straight ahead with zero steering angle applied (i.e. zero-toe) and that adding 1 degree of steering angle causes both the front tyres to have 1 degree of slip angle then they both generate the same thrust, but due to the effects described in earlier posts, the outside tyre contributes a little less to the yaw moment due to its drag moment being out of the turn, agree?

case 2: Now if we add 1 degree of toe out to both wheels and then add one degree of steering angle (causing 2 degrees of slip angle on the inside tyre and the outside tyre to be straight ahead) then the thrust from the outside tyre will be zero, and the thrust from the inside tyre is twice that of the inside tyre in the first case. Since the lateral force and the drag force on an inside tyre both cause a positive yaw moment into the corner then in this case the total yaw moment is higher than the first case, and the car turns in faster...

Again, I just want to clarify what you're recommending versus what I've read elsewhere.

 

[stuntman]

The outside tire has more effect on the car than the inside tire, and as weight is transferred to the outside, it's influence becomes greater as the inside tire's influence becomes less.

In the example you posted, its similar to what I said in my previous post. With toe-out, the outside tire has to reach zero toe before turning into the direction of the corner. Once the outer tire turns into the direction of the corner, it has to build a certain slip angle in the tread and tire carcass before it generates lateral force (grip to turn the car). Meanwhile, the inner tire does turn more in the direction of the corner, but as weight is transferred off it, it becomes less beneficial and does not have the same authority as the outer tire (which your quote incorrectly assumes). All of this is a delay that causes a less responsive and vague turn-in.

With Toe-IN, the outer tire is pre-loaded to a certain degree in the direction of the turn. As the wheel is turned, the time it takes to build enough slip angle to generate a lateral force is reduced (compared to toe-out) and the car responds quicker, especially as load is transferred to the outer tire giving it more authority. While the inside tire has to pass zero toe before turning into the corner, load is taken off the tire as it is transferred to the outer tire and its effect becomes less.

Now once the outer tire reaches its peak slip angle (whatever that may be and will depend on the tire, and many suspension geometry factors), static toe-IN will have less lateral force generation than toe-out. Depending on many factors in the car's suspension geometry, the point where the outer tire reaches its optimum slip angle will vary, so the crossover where toe-IN's improved turn-in and toe-out's improved mid-corner (and total) front grip will vary as well.

All of these are generalizations and there are always exceptions, but if you're driving at such low speeds (like an autocross), the turn-in benefit of toe-in will be very little and possibly non-existent and the (generally) benefit of overall front grip from toe-out (which can start closer to turn-in depending on the car and speed) would probably be more desirable.