m3 rear bar myth: let`s finish this!!

[GaryS]

Originally Posted by Stohlen

Ah... so this is the real issue. Its not that the rear bar makes the car slower, its that it makes it more likely for the driver to spin, and thus he as a precaution lets off the throttle more and takes a more conservative line. Which of course takes longer.

What it comes down to is that the rear bar is sufficient for the stock setup and any average driver won't have the skills to push the car when a larger bar is added. I'm sure race car drivers would love the lack of roll, and would be more likely to eliminate the tailhappiness that is added.

I know alot of people on here complain about understeer, and i would think a larger rear bar would help make their car more balanced. I know I haven't had that experience tho, as my car is slightly tailhappy as is, even with a 265 tire.

Very imaginative, but no. Dinan and HPA Shop are not idiots. Real race drivers tested the various swaybars in real cars on real race tracks. Theories are good, but facts are better.

[flinchy]

Originally Posted by Stohlen

Ah... so this is the real issue. Its not that the rear bar makes the car slower, its that it makes it more likely for the driver to spin, and thus he as a precaution lets off the throttle more and takes a more conservative line. Which of course takes longer.

What it comes down to is that the rear bar is sufficient for the stock setup and any average driver won't have the skills to push the car when a larger bar is added. I'm sure race car drivers would love the lack of roll, and would be more likely to eliminate the tailhappiness that is added.

I know alot of people on here complain about understeer, and i would think a larger rear bar would help make their car more balanced. I know I haven't had that experience tho, as my car is slightly tailhappy as is, even with a 265 tire.

Thicker rear INCREASES tail happiness (oversteer).. This doesn't mean that understeer is reduced, however..
Front sway CAN increase understeer, but in the 1ers case it actually makes it a bit easier to corner, makes the front more responsive.

[Stohlen]

Originally Posted by GaryS

Very imaginative, but no. Dinan and HPA Shop are not idiots. Real race drivers tested the various swaybars in real cars on real race tracks. Theories are good, but facts are better.

I didnt say they were idiots, i'm just trying to understand where their data comes from. Since they just tell me, we tested a bunch... cuz that means nothing. I could go out and test a bunch of exhaust systems all tell you which was better based on my butt dyno, but that wouldnt mean shit to anyone.

I wanna know based on design why an increased size hampers performance. And possible see the test data, understand how many tests were done and if there were with the same drivers. Too many variables and not enough test laps can make a source unreliable.

As far as i understand (and my knowledge base in suspension is not as strong as other areas) a stiffer rear staw bar is going to allow for the car to roll through the corners at an increased speed because it will more evenly balance weight distribution among the wheels, increasing traction on the inside wheel. I.e. there wont be as much weight on the outer wheel. Of course an LSD that can balance the force between the two wheels will take advantage of this and increase the amount of throttle possible when moving through and exiting the corners without spinning the wheels. A proper driver without an LSD would roll the car through the corners and power out on the exits taking a different line to maximize speed in. From what i've learned, this method would be faster with a stiffer rear bar than the standard method of taking a corner with a balanced car. I've never seen a car get slower from a stiffer rear sway bar before when driven properly, but that doesnt mean it cant happen. Just trying to understand.

[Stohlen]

Originally Posted by flinchy

Thicker rear INCREASES tail happiness (oversteer).. This doesn't mean that understeer is reduced, however..
Front sway CAN increase understeer, but in the 1ers case it actually makes it a bit easier to corner, makes the front more responsive.

The steering of a vehicle is one singular motion. How can you increase oversteer and still have the same understeer?

[fourtailpipes]

Originally Posted by Stohlen

a stiffer rear staw bar is going to allow for the car to roll through the corners at an increased speed because it will more evenly balance weight distribution among the wheels, increasing traction on the inside wheel. I.e. there wont be as much weight on the outer wheel.

you have this backwards. a stiffer swaybar serves to REDUCE traction from the inside tire by increasing comparative loading of the outside tire. this is why a stiffer rear bar can cause the e-diff to underperform.

[pixelblue]

if you're car is setup too stiff you'll just slide around and won't be fast despite the lack of body roll. setup too soft and you will be slow recovering from excessive yaw. the trick is to find the sweet spot in between too stiff and too soft where a little mechanical grip along with many other variables (alignment, tire size/pressure, aero, etc.) can add traction and speed. also if you add grip to one end you'll lose grip on the other end. so depending on your driving style you can fine tune and get the car to do exactly what you want. most expert drivers prefer a suspension that is tuned to be a little tail happy. our cars suspension is tuned from the factory to understeer for obvious safety reasons considering the high hp and the propensity to oversteer and potentially wrap the car around a tree. finding that perfect balance is what all race teams strive for

[flinchy]

Originally Posted by Stohlen

The steering of a vehicle is one singular motion. How can you increase oversteer and still have the same understeer?

Hm, poorly worded.. You can increase the tendency for the back to go out without increasing (or decreasing) actual front end grip... The front hits the corner first, if you go in hard, the front will lose traction before the rear even has a chance to lose it.

[HP Autowerks]

Originally Posted by AnooooOH

could you give me an explanation for "flatter" pls, I don`t know the word and couln`t find it in the dict.

so maybe schnitzer uses them, because their consumers aren`t racedrivers and they wanted to give them a more planted car?

what other suspensions mods were installed on the test car?

less body roll.

[Stohlen]

Originally Posted by fourtailpipes

you have this backwards. a stiffer swaybar serves to REDUCE traction from the inside tire by increasing comparative loading of the outside tire. this is why a stiffer rear bar can cause the e-diff to underperform.

A stiffer bar puts more weight on the inside tire, how does more weight reduce its traction?

[Stohlen]

Originally Posted by flinchy

Hm, poorly worded.. You can increase the tendency for the back to go out without increasing (or decreasing) actual front end grip... The front hits the corner first, if you go in hard, the front will lose traction before the rear even has a chance to lose it.

Gotcha, this makes more sense. I figured you ment it more in a driving style way than a singular moment way.

[fourtailpipes]

Originally Posted by Stohlen

A stiffer bar puts more weight on the inside tire, how does more weight reduce its traction?

a stiffer bar puts LESS weight on the inside tire, thereby reducing its traction.

[Stohlen]

Stiffen the bar = less body roll = more balanced weight = more weight on the inside tire than one with more body roll.

[Purple Derple]

Alright, long read ahead. Get some snacks. Have an open mind, there actually is some collective wisdom in this thread,

Originally Posted by Stohlen

The steering of a vehicle is one singular motion. How can you increase oversteer and still have the same understeer?

Like Gary and Flinchy and others have said, increasing oversteer tendency does not necessarily reduce understeer. You can have a car that is both tight and loose. For example, a car that pushes on turn in and mid corner, and is loose on exit. My guess is this is how a 1 series would behave with a overly thick rear anti-roll bar. What a miserable handful that would be! If you've ever driven in the rain, a car does this exact thing pretty willingly.

Originally Posted by Stohlen

As far as i understand (and my knowledge base in suspension is not as strong as other areas) a stiffer rear staw bar is going to allow for the car to roll through the corners at an increased speed because it will more evenly balance weight distribution among the wheels, increasing traction on the inside wheel. I.e. there wont be as much weight on the outer wheel.

Anti-roll bars primarily behave like springs on that end of the car. However, they cannot affect the total load that is transfered from side to side. In fact, there is NOTHING you can do to the suspension to affect how much load transfers besides lowering the ride height. So no, a stiffer rear or front for that matter bar wont more lead to a more balanced car necessarily in the sense of evenly distributing weight over all four contact patches. It would simply defy phsyics. So while the car may remain flatter, it still transfers just as much load in the corner.

Let me quote for you. I know it is poor form to use such a big block quote, but he demonstrates the concept better than I can. Carl Lopez writes in Going Faster!: Mastering the Art of Race Driving, "To Illustrate how spring rates affect the cornering balance of the car, let's go to an extreme and see what happens...the front springs and shocks [are] removed and replaced by solid bars, essentially making the front suspension solid...whe the car corners and the load transfers, all of the... load will be absorbed by the outside front tire (assuming an infitnitely rigid chassis), since the front end resists all the rolling motion of the car. The outside rear tire doesn't contribute to any of this and consequently retains 100% of its original grip. The outside front, because of all this extra load, suffesrs a loss in CF relative to the rear and as a result operates at a higher slip angle than the rear tire will. The car goes into understeer--in this case, probably pretty gross understeer--as the outside front is hopelessly overtaxed." He goes on to show a similar example for the rear, which to this thread is most relevant; "Now, lets put the shock/spring unit back on the front of the car and make the rear suspension solid. Under cornering...all the load transfer goes to the outside rear tire, causing the rear end to operate at higher slip angles--the definition of oversteer. What you're seeing here is the world's stiffest spring, one with a spring rate of a million pounds per inch, or so. Nobody would really do this to a poor car, but it helps to illustrate the principle. All other things equal, a stiffer spring will increas the resistance to roll and absorb more of the load transfer at the end of the car on which it is installed." So, "At the rear, a stiffer spring increases the tendency toward oversteer, while a softer one goes in the opposite direction, decreasing the oversteer tendency and increasing the tendency toward understeer."

Since we know anti-roll bars behave just like springs that resist lateral motion only, we can substitue the spring concept in that passage with the anti-roll bar concept to understand its behavior. Because of this behavior, anti roll bars are used to tune front to back handling balance, just like you thought. But of course there is much nuance and dark art to suspension tuning. Spring rates and damper rates are used primarily while anti-roll bars are used for more fine tuning. For some more thoughts about it, check out this thread started by the pro driver, racing coach and and author Ross Bentley, http://www.m3post.com/forums/showthread.php?t=759078 I also reccomend his books. They're totally mental and are applicable to more than just race driving. I was reallysurprised to see him post on the forum actually and encourage everyone to pick his brain--I know I will.

Likewise, given that you cannot change the total load transferred, a flatter car is not necessarily faster, depending on the circuit. Indeed, take a track that does not have transition corners like MR Laguna Seca for example. A relatively compliant suspension is faster at the track because compliance = grip at the cost of transitional weight management given that the car does not bottom out and that the suspension geometry doesn't overly roll into challenges. But managing transitional weight is not the priority when the track has 1 transitional corner and it is low speed and leads onto a downhill section like at Laguna Seca. So it is not rewarding to tune the car to a relatively unimportant corner.

Gary said more lively as in easier to spin as in less grip in the rear as in less ability to put power down and we can see why. That is definitely not faster. Nothing to do with driver confidence as a fast drive will driver as fast as the car can go no matter how stupid the car behaves.

[AnooooOH]

But my square setup is pretty neutral!
I want to add the front AND the rear bar.
Wouldnt this keep the neutral behaviour?

What can I do to have a more planted feeling?

[Focusedintntions]

Purp Derp...i think this is the nicest and most constructive post you've ever made on here haha...thanks mate!

Originally Posted by Purple Derple

Alright, long read ahead. Get some snacks. Have an open mind, there actually is some collective wisdom in this thread,



Like Gary and Flinchy and others have said, increasing oversteer tendency does not necessarily reduce understeer. You can have a car that is both tight and loose. For example, a car that pushes on turn in and mid corner, and is loose on exit. My guess is this is how a 1 series would behave with a overly thick rear anti-roll bar. What a miserable handful that would be! If you've ever driven in the rain, a car does this exact thing pretty willingly.


Anti-roll bars primarily behave like springs on that end of the car. However, they cannot affect the total load that is transfered from side to side. In fact, there is NOTHING you can do to the suspension to affect how much load transfers besides lowering the ride height. So no, a stiffer rear or front for that matter bar wont more lead to a more balanced car necessarily in the sense of evenly distributing weight over all four contact patches. It would simply defy phsyics. So while the car may remain flatter, it still transfers just as much load in the corner.

Let me quote for you. I know it is poor form to use such a big block quote, but he demonstrates the concept better than I can. Carl Lopez writes in Going Faster!: Mastering the Art of Race Driving, "To Illustrate how spring rates affect the cornering balance of the car, let's go to an extreme and see what happens...the front springs and shocks [are] removed and replaced by solid bars, essentially making the front suspension solid...whe the car corners and the load transfers, all of the... load will be absorbed by the outside front tire (assuming an infitnitely rigid chassis), since the front end resists all the rolling motion of the car. The outside rear tire doesn't contribute to any of this and consequently retains 100% of its original grip. The outside front, because of all this extra load, suffesrs a loss in CF relative to the rear and as a result operates at a higher slip angle than the rear tire will. The car goes into understeer--in this case, probably pretty gross understeer--as the outside front is hopelessly overtaxed." He goes on to show a similar example for the rear, which to this thread is most relevant; "Now, lets put the shock/spring unit back on the front of the car and make the rear suspension solid. Under cornering...all the load transfer goes to the outside rear tire, causing the rear end to operate at higher slip angles--the definition of oversteer. What you're seeing here is the world's stiffest spring, one with a spring rate of a million pounds per inch, or so. Nobody would really do this to a poor car, but it helps to illustrate the principle. All other things equal, a stiffer spring will increas the resistance to roll and absorb more of the load transfer at the end of the car on which it is installed." So, "At the rear, a stiffer spring increases the tendency toward oversteer, while a softer one goes in the opposite direction, decreasing the oversteer tendency and increasing the tendency toward understeer."

Since we know anti-roll bars behave just like springs that resist lateral motion only, we can substitue the spring concept in that passage with the anti-roll bar concept to understand its behavior. Because of this behavior, anti roll bars are used to tune front to back handling balance, just like you thought. But of course there is much nuance and dark art to suspension tuning. Spring rates and damper rates are used primarily while anti-roll bars are used for more fine tuning. For some more thoughts about it, check out this thread started by the pro driver, racing coach and and author Ross Bentley, http://www.m3post.com/forums/showthread.php?t=759078 I also reccomend his books. They're totally mental and are applicable to more than just race driving. I was reallysurprised to see him post on the forum actually and encourage everyone to pick his brain--I know I will.

Likewise, given that you cannot change the total load transferred, a flatter car is not necessarily faster, depending on the circuit. Indeed, take a track that does not have transition corners like MR Laguna Seca for example. A relatively compliant suspension is faster at the track because compliance = grip at the cost of transitional weight management given that the car does not bottom out and that the suspension geometry doesn't overly roll into challenges. But managing transitional weight is not the priority when the track has 1 transitional corner and it is low speed and leads onto a downhill section like at Laguna Seca. So it is not rewarding to tune the car to a relatively unimportant corner.

Gary said more lively as in easier to spin as in less grip in the rear as in less ability to put power down and we can see why. That is definitely not faster. Nothing to do with driver confidence as a fast drive will driver as fast as the car can go no matter how stupid the car behaves.

[AnooooOH]

Originally Posted by AnooooOH

But my square setup is pretty neutral!
I want to add the front AND the rear bar.
Wouldnt this keep the neutral behaviour?

What can I do to have a more planted feeling?

http://www.hpashop.com/product.sc?ca...3&productId=71

this sounds pretty good hp autowerks

so am I right that with my square setup it will be pretty neutral and I get better traction?

[Purple Derple]

sure if you believe this then spend away. none of this is marketing right?

Enhance the cornering performance of your BMW with a set of BMW oem M3 anti roll bars. The m3 anti roll bar package increases front/rear roll stiffness giving the car crisp, quick turn-in response and balanced handling. As delivered the E82/E9x 1 & 3 series has excessive under steer and limited roll control. M3 anti bars give the driver the ability to rotate the car on corner entry and steer with the throttle when necessary. The dreaded under steer is eliminated and the handling becomes comfortably neutral with added traction during cornering.

Features:

- Front sway bar-lightweight, durable tubular steel
- Rear sway bar-lightweight, durable tubular steel
- Come with all necessary bushing and bushing brackets(oem end-links are reused)

Benefits:

* Increased Traction.
* Reduced Body Roll
* Increased Vehicle Stability
* Crisper Cornering
* Easy Installation
* OEM Fitment

[AnooooOH]

def sounds like everything I`m searching for!

but because if the marketing thing I`d like to hear some opinions!

But imo this should work out:
square tire setup + m3 front AND m3 rear bar = same neutral feeling and more traction

[fourtailpipes]

Originally Posted by AnooooOH

def sounds like everything I`m searching for!

but because if the marketing thing I`d like to hear some opinions!

But imo this should work out:
square tire setup + m3 front AND m3 rear bar = same neutral feeling and more traction

with those tiny tires in the back, its doubtful that you'll generate enough lateral mechanical grip on that axle to pick up an inside rear tire anyway. you may not run into issues with the diff, but if you don't, it'll only be because you'll be carrying less speed than you could be and therefore loading the axle less.

take the diff out of the equation for a moment... adding a stiffer swaybar to the rear axle while also reducing the rear tire width from 245 to 225 is going to cause a substantial impairment on the grip generated by that axle.

and for what its worth, in modern times, ac schnitzer is kind of a joke. more of an authority on hideous body kits than chassis dynamics.

[int2str]

AnooooOH, I know you're looking for a simple answer, but I don't think there is one.

You say you want "more stability" and don't want to loose "traction". But it's not that easy. Where/when do you want more stability? Autobahn blasting? Fast corners? Slow corners? It all depends...

If you want more "Autobahn" stability, you're probably fine with a conservative alignment. An alignment can make a big difference in how the car feels. For long sweeping Autobahn turns, yes, maybe swaybars would help, but I'm not sure they'd be my first choice.

What about traction? Do you ever loose it? Doesn't sound like you do. I highly doubt that any suspension mod that you've mentioned so far (swaybars or no bars) will make a significant difference for daily driving. A rear swaybar will show it's effect the most on tight turns on mountain roads or other aggressive, fast, tight corners.

Regarding tires:
A square setup is the best choice in my opinion for a good balance and quick turn-in on our cars. Note that "good balance" is not the same as stability. A naturally under-steering car will always feel more stable than a well balanced car that's ready to turn.

If I had to start all over again I'd probably do this (and in this order):
1. Proper tires (Dunlop Star Specs; Michelin PSS etc.); 235 square probably
2. Camber plates and sportier alignment (note that this is for better turn-in; not stability)
3. Springs
4. Front swaybar
5. All 4 rear sub-frame bushings

Note that the swaybar is 2nd to last in that list....
Unless you've already done 1-3, I'm not sure I'd bother at all.

Now again, my goal is a well handling car, not a rail cart

If you're so bent on swaybars and can't make up your mind. Why not get the front first, run that for a while and if you don't like it, add the rear swaybar later down the road. Who knows, you might end up saving a bunch of money that way if you decide the rear bar isn't needed (which most of us think here)...

[Purple Derple]

Originally Posted by int2str

A rear swaybar will show it's effect the most on tight turns on mountain roads or other aggressive, fast, tight corners.

What is an aggressive, fast, tight corner?

[pixelblue]

Originally Posted by int2str

AnooooOH, I know you're looking for a simple answer, but I don't think there is one.

You say you want "more stability" and don't want to loose "traction". But it's not that easy. Where/when do you want more stability? Autobahn blasting? Fast corners? Slow corners? It all depends...

If you want more "Autobahn" stability, you're probably fine with a conservative alignment. An alignment can make a big difference in how the car feels. For long sweeping Autobahn turns, yes, maybe swaybars would help, but I'm not sure they'd be my first choice.

What about traction? Do you ever loose it? Doesn't sound like you do. I highly doubt that any suspension mod that you've mentioned so far (swaybars or no bars) will make a significant difference for daily driving. A rear swaybar will show it's effect the most on tight turns on mountain roads or other aggressive, fast, tight corners.

Regarding tires:
A square setup is the best choice in my opinion for a good balance and quick turn-in on our cars. Note that "good balance" is not the same as stability. A naturally under-steering car will always feel more stable than a well balanced car that's ready to turn.

If I had to start all over again I'd probably do this (and in this order):
1. Proper tires (Dunlop Star Specs; Michelin PSS etc.); 235 square probably
2. Camber plates and sportier alignment (note that this is for better turn-in; not stability)
3. Springs
4. Front swaybar
5. All 4 rear sub-frame bushings

Note that the swaybar is 2nd to last in that list....
Unless you've already done 1-3, I'm not sure I'd bother at all.

Now again, my goal is a well handling car, not a rail cart

If you're so bent on swaybars and can't make up your mind. Why not get the front first, run that for a while and if you don't like it, add the rear swaybar later down the road. Who knows, you might end up saving a bunch of money that way if you decide the rear bar isn't needed (which most of us think here)...

good advice!