Dialing out the understeer

[Doc]

Fully understand and agree with that Gambit.

It's not for lack of funds so much as lack of deisre to go 1.) too far so as to void warranty situations and 2.) too far.

I've already done the too far thing with the weekender so much so that the only real time I enjoy driving it now is either on track or at jailtime-serving speeds as it's otherwise just too harsh for Sydney roads.

This was a venture into an as yet unknown to glean those basic ideas behind what folks who ARE super passionate about their Liberties are doing. And I think I've gotten a bit to go on.



The one thing still has me puzzled is 'klks' comment about upping the rear spring rates to "6Kg". As in about 13 lbf ??? Or what conversion is he using?

[Dropz]

Dialing out understeer:

Get a wheel alignment (factory is fine, but I use 1mm toe out front, 0mm toe rear, -0.9 camber front and my rear is stuffed somehow so its stuck at -1.4), set your tyre pressures to your liking (I use 36psi, 38 in winter), drive properly.

The biggest thing that will make a difference is the last step (drive properly)
learn to heel-toe.
brake early so you can brake lighter, that way you have less forward momentum into the corner
trail brake.
don't throw the car hard into a corner, ease the car in and out.
learn the roads you are driving, learn the bumps, the camber, manholes (less traction), distances between corners, what gears have the right engine braking or accelerating power at each corner and straight.

Slow is smooth, smooth is fast. - Shooter (2007)

[BJ]

The one thing still has me puzzled is 'klks' comment about upping the rear spring rates to "6Kg". As in about 13 lbf ??? Or what conversion is he using?

6 kg/mm as in kg force. It isn't a proper SI unit but it's how the spring sellers rate their springs.

[Doc]

Dialing out understeer:

Get a wheel alignment (factory is fine, but I use 1mm toe out front, 0mm toe rear, -0.9 camber front and my rear is stuffed somehow so its stuck at -1.4), set your tyre pressures to your liking (I use 36psi, 38 in winter), drive properly.

Nifty. Solution in a box. Tks Dropz. That's a nice starting point.

The biggest thing that will make a difference is the last step (drive properly)
learn to heel-toe.
brake early so you can brake lighter, that way you have less forward momentum into the corner
trail brake.
don't throw the car hard into a corner, ease the car in and out.
learn the roads you are driving, learn the bumps, the camber, manholes (less traction), distances between corners, what gears have the right engine braking or accelerating power at each corner and straight.

Yes, tks. Grandma,.... eggs. But I do agree.

[coyote]

Understeer is caused by load on the outside front which is disproportionate to the load on the outside rear. I am not talking about turn in here but the understeer experienced in a steady cornering maneuver such as driving in a circle. There are several things which will help. A larger rear anti sway bar is the first. It will transfer more of the cornering induced weight transfer to the rear, and hence unload the outside front. The Whiteline Anti Lift Kit is another device to help with this, by reducing the wheel lift effect on the inside front. Also consider the Whiteline Roll Center adjustment kit.
Increasing the castor on the front will help significantly but this is usually only possible with coilovers.

Next would be to increase the rear spring rates.

To improve the turn in feel increased camber makes a big difference BUT can have a major effect on front tyre wear.

I'm sorry, but this is almost completely wrong.

Please enlighten us with your knowledge, or I will consider this just a troll

You may consider my statement of fact however you like.

[XT_for_me]

If you aren't understeering, you are not going quick

I had a good laugh, thanks.
Lets translate a couple of things into actual technical terms. I was trying to avoid them as the OP doesn't appear to have an indepth understanding of suspension.
Understeer is a term that is commonly used to describe the condition where the front tyres are operating at a greater slip angle than the rear tyres.

This has nothing to do with speed, although it becomes more obvious at higher slip angles which are induced by higher cornering forces, and hence higher speeds.

And remember with no understeer there is no grip. It's a fundamental requirement of physics to exist.

Errrr, no. There is absolutely no requirement of physics which relates understeer and grip. I think you are confused with the requirement to have slip angle to have lateral force. A very different thing, and as explained above the understeer or oversteer feel related to the relative slip angles of the front and rear tyres.

Understeer is caused by load on the outside front which is disproportionate to the load on the outside rear.

Wow this is wrong. What does 'load' have anything to do with it. I guarantee not one vehicle in the entire world loads both front and rear tyres proportionally 50% in any condition, ever.
Actually the term load was not technically correct the way I used it, I apologize. As I said above I was trying to avoid technical terms. what I meant was that the slip angle at the front is larger than the slip angle at the rear. The slip angle (both front and rear) is actually a result of a number of factors including lateral force (or centripital force if you prefer), the vertical load (caused by both static vehicle mass and mass transfer, seen as body roll), the tyre contact pressure and area, the contact pressure gain or fall off along the contact patch, the co-efficient of friction between the tyre and the ground, the degree of squirm which is related to the rubber compound, hardness and the tread pattern. Oh, I didn't mention lesser effects of temperature and humidity ( assuming we are not considering 100% humidity, IE: wet)

I am not talking about turn in here but the understeer experienced in a steady cornering maneuver such as driving in a circle.

So you are saying that you want to fix neutral rake understeer? This is not a commodore forum.

There is never a point in a subarus life that it is neutrally cornering. You are braking or accelerating.
Ummmm I am pretty sure I said something about steady state cornering. This was specifically because we are talking about chassis behavior or balance as opposed to something induced by the drive line responding to the right foot. Vehicle response to the right foot is a totally different and far more complex discussion. The fact that Subaru's typically have a much higher rear roll center than front, leading to significant changes in attitude with power on or off has very little to do with basic chassis balance.

There is no neutral rolling around a corner, if you are, you are slow. Fix being slow before fixing non existent problems.
This is totally irrelevant to the discussion.

The fact the front end will lose grip before the rear end is nearly a guaranteed design feature in every single passenger vehicle on the planet just about,
Agreed, its a safe behavior for the average driver.

and should remain that way.
If you are an average driver.

A front tyre is doing probably about 20% more work than a rear tyre in this condition you describe. This condition also never really exists unless you're driving a live axle. Because a front tyre works so much harder than a rear tyre, it will inherently fail first. To change this is not increasing rear end grip, it is decreasing front end grip. I said quite clearly, that without understeer, there is no cornering.
The degree of "work" being done has little relevance to the neutrality or otherwise of a chassis. Porsche for example are very well recognised for the great handling cars they make, but some are front engine, rear drive, some are rear engine, rear drive, some front engine all wheel drive, some rear engine all wheel drive, and lastly, some are mid engine rear wheel drive. Some how Porsche manage to make all of those combinations very close to neutral in chassis balance.

There are several things which will help.

Stop reading here is the first bit of help I can suggest to anyone

A larger rear anti sway bar is the first. It will transfer more of the cornering induced weight transfer to the rear, and hence unload the outside front.

Im going to need you to put this into a diagram for me, as this makes absolutely no sense what so ever to anyone who has ever driven a car
And I thought I had expressed it as simply as possible. The way a rear anti sway bar works is to increase the effective spring rate of the outside wheel in a corner. It has much the same effect as fitting a higher rate rear spring, which you advocate, except that it doesn't affect ride comfort in a straight line.

The Whiteline Anti Lift Kit is another device to help with this, by reducing the wheel lift effect on the inside front.

It doesnt reduce shit. It increases castor, scrub radius, and reduces the effective spring rate due to the increase in control arm moment. It has nothing to do with wheel lift (whatever loose term that is you are describing), and the anti squat characteristics are negligable. Tyre pressure is an easier way to achieve that one side benefit.
OK, we need to discuss specifics of the Liberty model here as there have been two different devices from Whiteline called an Anti Lift Kit. In the early Liberty models is was literally an anti lift device, but in the later models is is purely a castor adjustment. Either way, it will help reduce understeer in a constant cornering maneuver. Tyre pressure differences between front and rear tyres can certainly assist. Usually a 10% to 20% higher pressure in the front than in the rear will help. Experimentation is the best way to determine the right balance.

Also consider the Whiteline Roll Center adjustment kit.

There is nothing wrong with the front roll centre on a stock height gen4 liberty. Why would you want to increase bump steer? On a lowered liberty, sure...which is a completely different issue.
Yeah sort of, except that the rear roll center is much higher than the front roll center. You can easily test this for yourself. Find a nice empty circular roundabout and drive around it, applying a little power, then back off the power. You will notice that when you back off the power there is a distinct tendency for the rear to step out, which is a strong indicator of the difference in roll centers, front to rear. Raising the front roll center will assist with this, producing a more neutral chassis.

Increasing the castor on the front will help significantly but this is usually only possible with coilovers.

At which point in a corner will increased castor help reduce understeer? Because it wont in the scenario you described above. On corner entry...shit yes. Corner exit? hell no.
Actually the effect of increased castor is present at all stages of a corner. The way it works is to assist in evening out the contact patch pressure laterally by providing a shorter distance between the rim and the ground on the inside of the tyre than exists on the outside, thereby compressing the inner sidewall.

Next would be to increase the rear spring rates.

This should be absolutely first before anything else
I disagree because the same effect can largely be achieved with a larger rear anti sway bar, which has minimal effect on ride comfort. Increasing the spring rate always produces issues with finding a shock absorber to match, unless you move to coilovers with adjustable damping.

To improve the turn in feel increased camber makes a big difference BUT can have a major effect on front tyre wear.

turn in feel??? who cares about feel. We want to increase point to point speed. If it feels shit, thats a characteristic you're going to have to embrace. Want it to 'feel' nice, add 3mm of toe out and 50psi in the tyres with a 20mm wheel spacer on each front wheel. I guarantee you will 'feel' every single stone and rock and know exery single treadblock in your tyre....But it isnt fast. Increasing front camber serves a good purpose until such point as it begins to cost out corner grip. Tyre wear is non existent for anyone who contemplates going around a corner fast

Increased camber has a similar (but not the same) effect as increased castor, but on a street car it can have two major disadvantages. The obvious one is decreased tyre life due to excessive wear on the inside shoulder of the tyre. The less obvious is that in a straight line the contact patch of the tyre is compromised and this can badly affect braking grip. I do not recommend it for this reason.

[Doc]

Lets translate a couple of things into actual technical terms. I was trying to avoid them as the OP doesn't appear to have an indepth understanding of suspension.

errrr..... Thanks but tech away all you like. Rest assured if there's something I don't get, I'll ask.

There is nothing wrong with the front roll centre on a stock height gen4 liberty. Why would you want to increase bump steer? On a lowered liberty, sure...which is a completely different issue.
Yeah sort of, except that the rear roll center is much higher than the front roll center. You can easily test this for yourself. Find a nice empty circular roundabout and drive around it, applying a little power, then back off the power. You will notice that when you back off the power there is a distinct tendency for the rear to step out, which is a strong indicator of the difference in roll centers, front to rear. Raising the front roll center will assist with this, producing a more neutral chassis.

I would think that the behaviour described above, in its purest form, would occur irrespective of roll-centres, purely due to the effects of weight transfer. A higher rear roll-centre would of course, serve to exacerbate the behaviour. No?

Increasing the castor on the front will help significantly but this is usually only possible with coilovers.

At which point in a corner will increased castor help reduce understeer? Because it wont in the scenario you described above. On corner entry...shit yes. Corner exit? hell no.
Actually the effect of increased castor is present at all stages of a corner. The way it works is to assist in evening out the contact patch pressure laterally by providing a shorter distance between the rim and the ground on the inside of the tyre than exists on the outside, thereby compressing the inner sidewall.

IINM, camber and castor actually work together in a (ignoring driver inputs) steady state cornering environment. More castor = more proportionally increased camber the greater the slip angle. No?

As a simple experiment, hold a CD upright. Place your pointer and index fingers either side of the centre hole directly above and below and turn the CD - towards the back of your "A-arms" hand. Now return to straight and rotate your fingers around the centre point such that the upper is rearward of the lower. Now turn the wheel again.

By the same token, where too much -ve camber effects both wear and contact patch (obviously important for stopping), too much castor affects both steering weight and the desire to return to centre and (to a lesser extent) the tendency to tramline. No?

[XT_for_me]

Lets translate a couple of things into actual technical terms. I was trying to avoid them as the OP doesn't appear to have an indepth understanding of suspension.

errrr..... Thanks but tech away all you like. Rest assured if there's something I don't get, I'll ask.

There is nothing wrong with the front roll centre on a stock height gen4 liberty. Why would you want to increase bump steer? On a lowered liberty, sure...which is a completely different issue.
Yeah sort of, except that the rear roll center is much higher than the front roll center. You can easily test this for yourself. Find a nice empty circular roundabout and drive around it, applying a little power, then back off the power. You will notice that when you back off the power there is a distinct tendency for the rear to step out, which is a strong indicator of the difference in roll centers, front to rear. Raising the front roll center will assist with this, producing a more neutral chassis.

I would think that the behaviour described above, in its purest form, would occur irrespective of roll-centres, purely due to the effects of weight transfer. A higher rear roll-centre would of course, serve to exacerbate the behaviour. No?
Yes.

Increasing the castor on the front will help significantly but this is usually only possible with coilovers.

At which point in a corner will increased castor help reduce understeer? Because it wont in the scenario you described above. On corner entry...shit yes. Corner exit? hell no.
Actually the effect of increased castor is present at all stages of a corner. The way it works is to assist in evening out the contact patch pressure laterally by providing a shorter distance between the rim and the ground on the inside of the tyre than exists on the outside, thereby compressing the inner sidewall.

IINM, camber and castor actually work together in a (ignoring driver inputs) steady state cornering environment. More castor = more proportionally increased camber the greater the slip angle. No?
Actually that is a pretty good way to describe it, except that the aim is to reduce the front slip angle. The ultimate in understeer is when you have full lock and the car ploughs straight ahead, with a massive slip angle. We want the opposite, minimum slip angle.

As a simple experiment, hold a CD upright. Place your pointer and index fingers either side of the centre hole directly above and below and turn the CD - towards the back of your "A-arms" hand. Now return to straight and rotate your fingers around the centre point such that the upper is rearward of the lower. Now turn the wheel again.

By the same token, where too much -ve camber effects both wear and contact patch (obviously important for stopping), too much castor affects both steering weight and the desire to return to centre and (to a lesser extent) the tendency to tramline. No?

Increasing the castor will, as you suggest, tend to increase steering weight and self centering action. With the amount of adjustment available with both a Anti Lift Kit and pillow ball coilovers fitted it's still not an issue. There is an advantage in that left to its own devices that car will tend to track straighter which I find great for a relaxed drive on the freeway, without being noticeable in the twisties.

You can see the amount of castor Mercedes use on their street cars.

[Stu]

To decrease understeer increase rear stiffness, ie bigger rear anti roll bar.

Negative.

Decreasing rear end grip is not removing under steer.

All changes should be made against the clock. A bigger anti roll bar in the rear is not faster. It just feels faster and is more snappy... So slow and loose. The rear bar rate does nothing to load the front tyres when increased.

Want to rid all under steer you need a wholistic approach.

A proper 'steer' tyre on the front. Federal 595rsr is the best value for money. I'm trying AD050 yoko's next.
Up the rear spring rate to about 6kg with stock fronts and remove the front sway bar completely.
Make new strut tops and aim for about 8 deg of castor. Using the factory bearings in a sandwiched heim joint would do fine. Ghetto pillowballs.
1.5 to 2deg neg camber in the front. 1 on the rear is heaps.
3mm toe out on all corners.

Replace every bush in the car with alloy or urethane.
Solid mount the rear subframe, diff, gearbox supports.

Once you start making power replace all 3 diffs. Once done you can add a front swaybar again. Until then it only serves to tripod the car keeping wheels off the ground.

With the above you'll our steer just about anything with a rego plate. You will also get 4-5k's max from a set of front tyres. Zero toe in the rear will stop the tram lining a little. Front toe out is needed. At least a mm.

Stock geometry is amazing at stock height. Stiffer rear also introduces some anti squat which helps corner exit front end grip a huge amount due to the stock dynamic toe.

Stock bilsteins are not valved hard enough as is.... Look at a proper set of shocks. Ohlins, dms etc.

I hereby nominate kiks for the official Liberty Club post of 2011

In all honesty I love reading all of your posts and can not wait until the next - and yes I will be fitting Federal 595rsr shortly THANKS!

[Kekotic]

Kiks for president.

[SH30RB]

Kiks for president.

+1

[BJ]

If you aren't understeering, you are not going quick

I had a good laugh, thanks.
Lets translate a couple of things into actual technical terms. I was trying to avoid them as the OP doesn't appear to have an indepth understanding of suspension.
Understeer is a term that is commonly used to describe the condition where the front tyres are operating at a greater slip angle than the rear tyres.

This has nothing to do with speed, although it becomes more obvious at higher slip angles which are induced by higher cornering forces, and hence higher speeds.

And remember with no understeer there is no grip. It's a fundamental requirement of physics to exist.

Errrr, no. There is absolutely no requirement of physics which relates understeer and grip. I think you are confused with the requirement to have slip angle to have lateral force. A very different thing, and as explained above the understeer or oversteer feel related to the relative slip angles of the front and rear tyres.

Understeer is caused by load on the outside front which is disproportionate to the load on the outside rear.

Wow this is wrong. What does 'load' have anything to do with it. I guarantee not one vehicle in the entire world loads both front and rear tyres proportionally 50% in any condition, ever.
Actually the term load was not technically correct the way I used it, I apologize. As I said above I was trying to avoid technical terms. what I meant was that the slip angle at the front is larger than the slip angle at the rear. The slip angle (both front and rear) is actually a result of a number of factors including lateral force (or centripital force if you prefer), the vertical load (caused by both static vehicle mass and mass transfer, seen as body roll), the tyre contact pressure and area, the contact pressure gain or fall off along the contact patch, the co-efficient of friction between the tyre and the ground, the degree of squirm which is related to the rubber compound, hardness and the tread pattern. Oh, I didn't mention lesser effects of temperature and humidity ( assuming we are not considering 100% humidity, IE: wet)

I am not talking about turn in here but the understeer experienced in a steady cornering maneuver such as driving in a circle.

So you are saying that you want to fix neutral rake understeer? This is not a commodore forum.

There is never a point in a subarus life that it is neutrally cornering. You are braking or accelerating.
Ummmm I am pretty sure I said something about steady state cornering. This was specifically because we are talking about chassis behavior or balance as opposed to something induced by the drive line responding to the right foot. Vehicle response to the right foot is a totally different and far more complex discussion. The fact that Subaru's typically have a much higher rear roll center than front, leading to significant changes in attitude with power on or off has very little to do with basic chassis balance.

There is no neutral rolling around a corner, if you are, you are slow. Fix being slow before fixing non existent problems.
This is totally irrelevant to the discussion.

The fact the front end will lose grip before the rear end is nearly a guaranteed design feature in every single passenger vehicle on the planet just about,
Agreed, its a safe behavior for the average driver.

and should remain that way.
If you are an average driver.

A front tyre is doing probably about 20% more work than a rear tyre in this condition you describe. This condition also never really exists unless you're driving a live axle. Because a front tyre works so much harder than a rear tyre, it will inherently fail first. To change this is not increasing rear end grip, it is decreasing front end grip. I said quite clearly, that without understeer, there is no cornering.
The degree of "work" being done has little relevance to the neutrality or otherwise of a chassis. Porsche for example are very well recognised for the great handling cars they make, but some are front engine, rear drive, some are rear engine, rear drive, some front engine all wheel drive, some rear engine all wheel drive, and lastly, some are mid engine rear wheel drive. Some how Porsche manage to make all of those combinations very close to neutral in chassis balance.

There are several things which will help.

Stop reading here is the first bit of help I can suggest to anyone

A larger rear anti sway bar is the first. It will transfer more of the cornering induced weight transfer to the rear, and hence unload the outside front.

Im going to need you to put this into a diagram for me, as this makes absolutely no sense what so ever to anyone who has ever driven a car
And I thought I had expressed it as simply as possible. The way a rear anti sway bar works is to increase the effective spring rate of the outside wheel in a corner. It has much the same effect as fitting a higher rate rear spring, which you advocate, except that it doesn't affect ride comfort in a straight line.

The Whiteline Anti Lift Kit is another device to help with this, by reducing the wheel lift effect on the inside front.

It doesnt reduce shit. It increases castor, scrub radius, and reduces the effective spring rate due to the increase in control arm moment. It has nothing to do with wheel lift (whatever loose term that is you are describing), and the anti squat characteristics are negligable. Tyre pressure is an easier way to achieve that one side benefit.
OK, we need to discuss specifics of the Liberty model here as there have been two different devices from Whiteline called an Anti Lift Kit. In the early Liberty models is was literally an anti lift device, but in the later models is is purely a castor adjustment. Either way, it will help reduce understeer in a constant cornering maneuver. Tyre pressure differences between front and rear tyres can certainly assist. Usually a 10% to 20% higher pressure in the front than in the rear will help. Experimentation is the best way to determine the right balance.

Also consider the Whiteline Roll Center adjustment kit.

There is nothing wrong with the front roll centre on a stock height gen4 liberty. Why would you want to increase bump steer? On a lowered liberty, sure...which is a completely different issue.
Yeah sort of, except that the rear roll center is much higher than the front roll center. You can easily test this for yourself. Find a nice empty circular roundabout and drive around it, applying a little power, then back off the power. You will notice that when you back off the power there is a distinct tendency for the rear to step out, which is a strong indicator of the difference in roll centers, front to rear. Raising the front roll center will assist with this, producing a more neutral chassis.

Increasing the castor on the front will help significantly but this is usually only possible with coilovers.

At which point in a corner will increased castor help reduce understeer? Because it wont in the scenario you described above. On corner entry...shit yes. Corner exit? hell no.
Actually the effect of increased castor is present at all stages of a corner. The way it works is to assist in evening out the contact patch pressure laterally by providing a shorter distance between the rim and the ground on the inside of the tyre than exists on the outside, thereby compressing the inner sidewall.

Next would be to increase the rear spring rates.

This should be absolutely first before anything else
I disagree because the same effect can largely be achieved with a larger rear anti sway bar, which has minimal effect on ride comfort. Increasing the spring rate always produces issues with finding a shock absorber to match, unless you move to coilovers with adjustable damping.

To improve the turn in feel increased camber makes a big difference BUT can have a major effect on front tyre wear.

turn in feel??? who cares about feel. We want to increase point to point speed. If it feels shit, thats a characteristic you're going to have to embrace. Want it to 'feel' nice, add 3mm of toe out and 50psi in the tyres with a 20mm wheel spacer on each front wheel. I guarantee you will 'feel' every single stone and rock and know exery single treadblock in your tyre....But it isnt fast. Increasing front camber serves a good purpose until such point as it begins to cost out corner grip. Tyre wear is non existent for anyone who contemplates going around a corner fast

Increased camber has a similar (but not the same) effect as increased castor, but on a street car it can have two major disadvantages. The obvious one is decreased tyre life due to excessive wear on the inside shoulder of the tyre. The less obvious is that in a straight line the contact patch of the tyre is compromised and this can badly affect braking grip. I do not recommend it for this reason.

Actually, this response from XT is the most accurate in this thread, which has been a very informative discussion.

[coyote]

viewtopic.php?f=3&t=15100

[bigBADbenny]

Great thread!
To summarize a little, to improve the handling of my stock MY07 GT-B wagon, and assuming none of the standard gear needs replacement, I should consider the following hardware:(from this thread)

solid rear swaybar
anti lift kit
roll center adjustment kit
(edit: quote: chaotic2050 @ viewtopic.php?f=38&t=5481)
Phats Front control arm lower bushes
Whiteline $50 Front control arm upper bushes (suggested by Jim)
Cusco front swaybar endlinks.

and wheel alignment (quote: Dropz @ this thread)
factory or 1mm toe out front, 0mm toe rear,
-0.9 camber front,
36/38psi

I drive it fairly gently but it does "tip" into corners a little, e.g. the left handed entry ramp from Hoddle to Eastern Freeway .

[XT_for_me]

Start with a Whiteline 20mm adjustable rear bar. If you still want to remove some understeer effect after that then fit the anti lift kit.