adjustable sway bars / oversteer question
Discussion
I have adjustable sway bars and a problem with terrible oversteer (relatively speaking). I know the oversteer problems comes from a fact that I have too stiff rear sway bar. Car has zero understeer.
So what I have done is to adjust rear sway bar to the most soft setting. This helped, but the oversteer problem is still there. And the front is still glued (still no sign of understeer)
And here's a theoretical question. I know I can help get the car more neutral if I stiffen the front sway bar. However I have a problem understanding what this would actually do to the car. People are saying that stiffen front sway bar will reduce oversteer. To me looks like it it adds understeer, which when combined with rear's lack of grip (oversteer) would result in a more neutral car. In other words - it doesn't really cure oversteer, only reduces grip in the front compensating for rear's lack of grip. So yes the car is more neutral, but in overall with less grip then right now when it oversteers...
So if my assumption is right, setting the front sway bar to its most stiff setting will PROPERLY cure the problem.
Can someone please comment. Thanks
PS My car is M3 E46.
So what I have done is to adjust rear sway bar to the most soft setting. This helped, but the oversteer problem is still there. And the front is still glued (still no sign of understeer)
And here's a theoretical question. I know I can help get the car more neutral if I stiffen the front sway bar. However I have a problem understanding what this would actually do to the car. People are saying that stiffen front sway bar will reduce oversteer. To me looks like it it adds understeer, which when combined with rear's lack of grip (oversteer) would result in a more neutral car. In other words - it doesn't really cure oversteer, only reduces grip in the front compensating for rear's lack of grip. So yes the car is more neutral, but in overall with less grip then right now when it oversteers...
So if my assumption is right, setting the front sway bar to its most stiff setting will PROPERLY cure the problem.
Can someone please comment. Thanks
PS My car is M3 E46.
Have you checked your corner weights?
Make sure they're they're in proportion side to side, and front to rear (on level ground). If you have any bias diagonally your car will handle like a dog. If you are going round a circuit you may wish to bias the settings side to side, but front to rear is more normal. Normally the adjustment you have front to rear will be vastly outweighed by the natural weight distribution in the vehicle.
You may be able to see the suspension taking the weight visually front to rear, but the only way to detect any diagonal bias is to actually measure the weights.
You can get a tool to do this, it's a pressure guage and a lever. The lever has a plastic end that you can safely use on the rims of your wheels to lift the corner on top of a hydraulic cylinder. The pressure guage allows you to measure the force required to lift the corner.
>> Edited by dilbert on Monday 14th February 06:29
Make sure they're they're in proportion side to side, and front to rear (on level ground). If you have any bias diagonally your car will handle like a dog. If you are going round a circuit you may wish to bias the settings side to side, but front to rear is more normal. Normally the adjustment you have front to rear will be vastly outweighed by the natural weight distribution in the vehicle.
You may be able to see the suspension taking the weight visually front to rear, but the only way to detect any diagonal bias is to actually measure the weights.
You can get a tool to do this, it's a pressure guage and a lever. The lever has a plastic end that you can safely use on the rims of your wheels to lift the corner on top of a hydraulic cylinder. The pressure guage allows you to measure the force required to lift the corner.
>> Edited by dilbert on Monday 14th February 06:29
Weight distribution is perfect. But thanks for pointing out. I'm quite sure my oversteer problem is due to too stiff rear sway bar. Question is, is it OK to try to fix it at the front sway bar, or do I have to find a softer rear sway bar (which is pretty much impossible as I couldn't find a company that would do something softer than Eibach and stiffer than stock...)
Well I could be wrong but I would have thought that you'd get more grip, with a stiffer suspension. I guess it'll break away more suddenly if it's stiff.
Softening it up will make it easier to guage, i.e. you'll get a more progressive break. You might also get better grip on rough surfaces.
Are you sure you wouldn't be better off with a long travel throttle?
>> Edited by dilbert on Monday 14th February 06:45
Softening it up will make it easier to guage, i.e. you'll get a more progressive break. You might also get better grip on rough surfaces.
Are you sure you wouldn't be better off with a long travel throttle?
>> Edited by dilbert on Monday 14th February 06:45
Well ask around, anyway.
I think that many people forget how much work goes into developing race cars. I was perfectly serious about the throttle. I'm sure it's the sort of thing that happens.
Better control and more power means a faster time.
>> Edited by dilbert on Monday 14th February 06:53
I think that many people forget how much work goes into developing race cars. I was perfectly serious about the throttle. I'm sure it's the sort of thing that happens.
Better control and more power means a faster time.
>> Edited by dilbert on Monday 14th February 06:53
You have my deepest sympathies. I have repeatedly tested stiffer anti roll bars and always end up going back to a properly located standard front and REMOVING the standard rear.
I got into the same loop with oversteer with any rear bar worth having. This was compensated my increasingly stiffening the front and ending up with a car with the same balance but slower.
My 'problem' is that I race on genuine road tyres and they didn't like stiff anti roll. When I tried the car on slicks they couldn't get enough anti roll bar.
Two questions -
- What tyres are you on?
- When stiffening the front are you readjusting the camber and castor to match?
I got into the same loop with oversteer with any rear bar worth having. This was compensated my increasingly stiffening the front and ending up with a car with the same balance but slower.
My 'problem' is that I race on genuine road tyres and they didn't like stiff anti roll. When I tried the car on slicks they couldn't get enough anti roll bar.
Two questions -
- What tyres are you on?
- When stiffening the front are you readjusting the camber and castor to match?
Denis
actually I read www.teamscr.com/sway.htm and it seems adjusting roll at the other end is actually OK. Because of the weight transfer.
So if I dial out oversteer by stiffening front sway bar, why the end result would be a balanced car but SLOWER?
Answer 1) My tyres are: Michelin PS2 and Michelin Pilot Sport Cup (DOT semi slicks). In both cases I get about the same amount of oversteer.
Answer 2) No I don't do any readjustments (does adjusting sway bars change caster/camber??). I have caster at max positive, and camber at -2deg at front and -2 deg rear.
actually I read www.teamscr.com/sway.htm and it seems adjusting roll at the other end is actually OK. Because of the weight transfer.
So if I dial out oversteer by stiffening front sway bar, why the end result would be a balanced car but SLOWER?
Answer 1) My tyres are: Michelin PS2 and Michelin Pilot Sport Cup (DOT semi slicks). In both cases I get about the same amount of oversteer.
Answer 2) No I don't do any readjustments (does adjusting sway bars change caster/camber??). I have caster at max positive, and camber at -2deg at front and -2 deg rear.
In general I would advise you to keep the overall roll stiffness the same and soften the front as you stiffen the rear, and vice versa. Changing the overall roll stiffness introduces a whole new load of variables working for and against you. Softening the rear and stiffening the front will discourage oversteer and encourage understeer. There's no right and wrong and no hard and fast rule about whether this will make you faster or slower. Something that makes your mate slower might make you faster. It all depends whether the car is biassed towards oversteer or understeer to start with, and whether you are a driver who prefers oversteer or understeer, and whether oversteer or understeer become an issue at the circuit you measure it at. Roll stiffness is the favorite way to adjust under-/oversteer because they do that with very little side effect, but there are other ways you can bias the grip to the front or the rear, or set the car up to be inherently stable or unstable. It's quite a complicated subject and if you're interested I recommend you get two or three boks and have a read round the subject. It's complicated by very rewarding to play with.
There are lots of arguments about fixing a problem by adjusting the other end, particularly with anti roll bars. There are a lot of variables involved and most people that are firmly entrenched in one camp forget about them.
In the end it comes down to what works in your instance. In my instance they don't.
What I found on my car is it wouldn't tolerate stiffer anti roll bars because of the extra side load on the tyre caused it too flex too much, negating any potential benefit.
Your tyres are probably both 'stickier' and have a stiffer sidewall than mine so I they can probably tolerate the extra side loading.
The point about suspension settings is if you reduce a cars roll and the car has inherently rubbish suspension geometry (like mine) then it will need adjusting to take advantage. On my car the less roll I have the less camber I need.
One obvious question, have you checked you have sufficient rear suspension movement? Remember you need to check for dampers bottoming out, springs going coil bound, suspension components hitting things, rear suspension links binding etc. Yes, I have had all the previous and at the same time!!!
In the end it comes down to what works in your instance. In my instance they don't.
What I found on my car is it wouldn't tolerate stiffer anti roll bars because of the extra side load on the tyre caused it too flex too much, negating any potential benefit.
Your tyres are probably both 'stickier' and have a stiffer sidewall than mine so I they can probably tolerate the extra side loading.
The point about suspension settings is if you reduce a cars roll and the car has inherently rubbish suspension geometry (like mine) then it will need adjusting to take advantage. On my car the less roll I have the less camber I need.
One obvious question, have you checked you have sufficient rear suspension movement? Remember you need to check for dampers bottoming out, springs going coil bound, suspension components hitting things, rear suspension links binding etc. Yes, I have had all the previous and at the same time!!!
At all three states.
My understanding:
- corner entry: could be due to late braking or unbalance between front and rear
- apex (no throttle): unbalance between front and rear
- corner exit: could be due to early acceleration or unbalance between front and rear
My understanding:
- corner entry: could be due to late braking or unbalance between front and rear
- apex (no throttle): unbalance between front and rear
- corner exit: could be due to early acceleration or unbalance between front and rear
rlk500 said:
At what state are you getting the oversteer? Steady throttle, lifting off or more throttle. This should give a better guide as to how to remedy your problem.
I'd just remove the rear bar and possibly soften the rear springs.
Lowering the car has probably upped the roll stiffness so much that it needs less roll anti roll bar than you have and possibly less spring stiffness.
You must bear in mind that a saloon car has an enormous amount of inertia, and at the limit it should have transient understeer with mid turn balance on the throttle and a modicum of opposite lock on the exit.
You cannot overcome the laws of Physics - the issue is that once the vehicle is turning you can't stop it - hence the oversteer.
That's why a good touring car driver will steer on the throttle, backing off slightly when you are in power oversteer increases grip and that maintains balance.
Lowering the car has probably upped the roll stiffness so much that it needs less roll anti roll bar than you have and possibly less spring stiffness.
You must bear in mind that a saloon car has an enormous amount of inertia, and at the limit it should have transient understeer with mid turn balance on the throttle and a modicum of opposite lock on the exit.
You cannot overcome the laws of Physics - the issue is that once the vehicle is turning you can't stop it - hence the oversteer.
That's why a good touring car driver will steer on the throttle, backing off slightly when you are in power oversteer increases grip and that maintains balance.
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