[Chowbow]

Originally Posted by MteK

Will these custom swaybar brackets and links be available for purchase seperately?

+1. I'd be interested in replacing my OEM swaybar bushings (the ones that mount to frame) with the GC ones. I do not want to go with larger diameter swaybars, just change out the bushings for a better "feel."

[HP Autosport]

Originally Posted by MteK

Any reason why you didn't go with HP on this? They seem to have worked out a complete m3 suspension swap some time ago, including custom components.

Also, I've installed the M3 sways and had no problem using the m3 brackets. What issues did you run into?

There is nothing wrong with the oem M3 bushing brackets. We have put them through many street and track miles without any issues...They are not noisy and requires no lubrication.


There is something about rod-ends people should know, they will slowly become noisy over time. If you often drive on rough roads, the noise will drive you crazy. Leave the rod-end links for dual purpose or race cars.


Fact: We were the first one to install the M3 components on the 335i and 135i. It's exciting to see everyone else is finally getting around to this.

[lonestar22]

do you align your car to M3 specs or regular specs?

[Speediance]

Originally Posted by lonestar22

do you align your car to M3 specs or regular specs?

I did M3 specs; I think. Again, it was done to Jay's recommendations. But I will post the specs soon, I think I have the post-alignment numbers lying around somewhere...

[eltoshan]

Ground Control kits are looking pretty good now a days, especially with dyno matched Koni sports!

Just a couple observations"

If you really want more control, though, I would suggest trying out some Hypercoil springs. At least the older Eibach springs were known to sag over time, and Hypercoil has just as good a selection of rates/ID/lengths.

Did you measure the motion ratios of rear? I have a feeling that 525/650 will be rather understeery unless the rear has an unusually high motion ratio for a multi-link setup. Doing some quick calculations with your corner weights show that 525lb/in springs on the front (struts, assume MR of .99 or so), results in a ~2.3Hz natural frequency, that's quite a harsh ride for street. For track you will need some very very sticky tires, or a very very smooth track. Using a sporty yet more compliant natural frequency of 1.8Hz, the proper spring rate for the front works out to be roughly 287lb/in.

[Speediance]

Originally Posted by eltoshan

Ground Control kits are looking pretty good now a days, especially with dyno matched Koni sports!

Just a couple observations"

If you really want more control, though, I would suggest trying out some Hypercoil springs. At least the older Eibach springs were known to sag over time, and Hypercoil has just as good a selection of rates/ID/lengths.

Did you measure the motion ratios of rear? I have a feeling that 525/650 will be rather understeery unless the rear has an unusually high motion ratio for a multi-link setup. Doing some quick calculations with your corner weights show that 525lb/in springs on the front (struts, assume MR of .99 or so), results in a ~2.3Hz natural frequency, that's quite a harsh ride for street. For track you will need some very very sticky tires, or a very very smooth track. Using a sporty yet more compliant natural frequency of 1.8Hz, the proper spring rate for the front works out to be roughly 287lb/in.

Eibachs come with, I believe, claim that springs wont sag for 1Million miles or something like that; I will see if that is true over time. Too early to tell. However, I am happy that these springs work well with the GC (custom valved Konis) shocks.

Its cool that you seem to know the math behind suspension dynamics; your point maybe irrefutable. But sometimes I've seen that conclusions based on pure math can be quite contradictory to the actual driving experiences. Anyways, I'd love to know more about the math if you could point me to some article/resource.

At the time of the post, I was running 430/550 springs, however, now I'm running 430/600. And according to my experience, the 430/600 ride is quite good even for San Francisco roads; very docile and tolerable. Not harsh, just firm, but BLOODY-WELL-DAMPED. And I like the 430/600 setup much more than the 430/550. I would strongly recommend it; its the best balance between ride-quality and performance.

In my initial thread, I merely suggested that a 525/650 would be a great entry level autocross/track setup. However, I've had the car for a week with 525/600 setup, and the front was not harsh AT ALL, however you'd feel a thud when entering a dip and short fly when going out of it AT freeway speeds. Now you know why I switched it to a 430/550 setup (during the time I wrote the initial thread). And it has now changed to 430/600.

I'm going to try out 500/650 setup. I will report back what I feel about it... However, I know that its going to "feel" much stiffer than what I have now. I am not sure how docile its going to be, but we'll see...

[HP Autosport]

Originally Posted by eltoshan

Ground Control kits are looking pretty good now a days, especially with dyno matched Koni sports!

Just a couple observations"

If you really want more control, though, I would suggest trying out some Hypercoil springs. At least the older Eibach springs were known to sag over time, and Hypercoil has just as good a selection of rates/ID/lengths.

Did you measure the motion ratios of rear? I have a feeling that 525/650 will be rather understeery unless the rear has an unusually high motion ratio for a multi-link setup. Doing some quick calculations with your corner weights show that 525lb/in springs on the front (struts, assume MR of .99 or so), results in a ~2.3Hz natural frequency, that's quite a harsh ride for street. For track you will need some very very sticky tires, or a very very smooth track. Using a sporty yet more compliant natural frequency of 1.8Hz, the proper spring rate for the front works out to be roughly 287lb/in.

Obviously, the motion ratios were meansured at all nor was any calculations done to come up with that rate. That is one rough riding street car with lots of understeer!

"Orb" and HP Autowerks already have all the math worked out over a year or year and a half ago. Lots of information have been posted here on E90post, even some suggested spring rates. Yet there will be others who go out on their own and try something they think might work or use they learn from the E36/46 days, which doesn't work on the E82/9X chassis at all.

[Speediance]

Originally Posted by HP Autowerks

Obviously, the motion ratios were meansured at all nor was any calculations done to come up with that rate. That is one rough riding street car with lots of understeer!

"Orb" and HP Autowerks already have all the math worked out over a year or year and a half ago. Lots of information have been posted here on E90post, even some suggested spring rates. Yet there will be others who go out on their own and try something they think might work or use they learn from the E36/46 days, which doesn't work on the E82/9X chassis at all.

Originally Posted by HP Autowerks

Obviously, the motion ratios were meansured at all nor was any calculations done to come up with that rate. That is one rough riding street car with lots of understeer!

"Orb" and HP Autowerks already have all the math worked out over a year or year and a half ago. Lots of information have been posted here on E90post, even some suggested spring rates. Yet there will be others who go out on their own and try something they think might work or use they learn from the E36/46 days, which doesn't work on the E82/9X chassis at all.

Hey HPAutowerks, it seems you know too much about my car and how it rides/handles without actually having sat in it...

I dont quite like how you responded; not at all professional of you. The 'smiley' is no excuse. So here is my response:

1) If you think you have all the math figured out and are obviously superior to others, than rest assured with that fact. There is NO reason to be defensive about it. Better products, better solutions always win! Have some faith!

2) I'm just a curious human being exploring all my options. And I'm simply sharing my experiences to people who I think would be most interested in finding them out. No one is being forced to read anything here; or atleast I hope not. I know, you are an active vendor here and a "suspension guru", but let me remind you, just like everyone else here on this forum, you dont have to read this! And if you think, I'm simply spewing garbage here, please find better use of your time.

3) You are most welcome to provide ideas and suggestions to make things better. It will only help the community out.

4) Please read my post previous to yours.

Apologies for the direct and forward tone, but I think its fair and deserved.

[HP Autosport]

Calculations were done as well as hours and hours of testing by "Orb", others, and myself. And I have driven on many E82/9x with various dampers and spring rates to make comparisons between them.

Suggestions are posted all over the place on this and other forums to help the community out, but why try something that is a given not to be an ideal set-up for our cars?

I apologize if you took it the wrong way, I meant to help you, not want you to go down the path of others on the forums.

If I remember correctly, I even gave you suspension suggestions over PM or phone several times in the past.

[Speediance]

Originally Posted by HP Autowerks

Calculations were done as well as hours and hours of testing by "Orb", others, and myself. And I have driven on many E82/9x with various dampers and spring rates to make comparisons between them.

Suggestions are posted all over the place on this and other forums to help the community out, but why try something that is a given not to be an ideal set-up for our cars?

I apologize if you took it the wrong way, I meant to help you, not want you to go down the path of others on the forums.

If I remember correctly, I even gave you suspension suggestions over PM or phone several times in the past.

Yes, I distinctly remember talking to you over phone and pm. And there is no doubt you know the stuff you sell. Thanks for your input/help.

But, its quite obvious your remark was crafted to undermine other people's knowledge/experience/satisfaction. Nonetheless, apology accepted.

[Orb]

Originally Posted by eltoshan

Ground Control kits are looking pretty good now a days, especially with dyno matched Koni sports!

Just a couple observations"

If you really want more control, though, I would suggest trying out some Hypercoil springs. At least the older Eibach springs were known to sag over time, and Hypercoil has just as good a selection of rates/ID/lengths.

Did you measure the motion ratios of rear? I have a feeling that 525/650 will be rather understeery unless the rear has an unusually high motion ratio for a multi-link setup. Doing some quick calculations with your corner weights show that 525lb/in springs on the front (struts, assume MR of .99 or so), results in a ~2.3Hz natural frequency, that's quite a harsh ride for street. For track you will need some very very sticky tires, or a very very smooth track. Using a sporty yet more compliant natural frequency of 1.8Hz, the proper spring rate for the front works out to be roughly 287lb/in.

At least someone is looking for the truth. Just to help you get to the bottom of this the motion ratio are:

F: 0.96^2 * spring rate = wheel rate
R: 0.57^2 * spring rate = wheel rate

The rear damper motion ratio is about 0.81

As you seem to know the frequancy is the only thing that matters.

Orb

[iAerodynamic]

wow very nice!

[tres]

this thread is very informative i welcome new ideas you can never stop learning iv'e seen in the past when some guys said you cant have certain mods done to your car and someone did it (like install an e92 m3 diff on an e92 335i ) everyone has their own taste you just have to find what works for you

[marconi118]

is the rear motion ratio of 335i the same as M3?

Is it linked to the ET of the wheel?

[eltoshan]

Originally Posted by Orb

At least someone is looking for the truth. Just to help you get to the bottom of this the motion ratio are:

F: 0.96^2 * spring rate = wheel rate
R: 0.57^2 * spring rate = wheel rate

The rear damper motion ratio is about 0.81

As you seem to know the frequancy is the only thing that matters.

Orb

Thank you very much! I've been guessing that the rear MR to be around 0.75 or so, but I had no idea it is that low. Goes to show what actually measuring things can do.

Originally Posted by marconi118

is the rear motion ratio of 335i the same as M3?

Is it linked to the ET of the wheel?

I still don't know nearly as much about our suspension as I should, but with a different offset wheel, the amount of leverage the wheel exerts on the spring is changed, so the motion ratio would be different as well. But that would not be nearly as drastic as having longer control arms, etc.

Originally Posted by Speediance

Eibachs come with, I believe, claim that springs wont sag for 1Million miles or something like that; I will see if that is true over time. Too early to tell. However, I am happy that these springs work well with the GC (custom valved Konis) shocks.

Its cool that you seem to know the math behind suspension dynamics; your point maybe irrefutable. But sometimes I've seen that conclusions based on pure math can be quite contradictory to the actual driving experiences. Anyways, I'd love to know more about the math if you could point me to some article/resource.

At the time of the post, I was running 430/550 springs, however, now I'm running 430/600. And according to my experience, the 430/600 ride is quite good even for San Francisco roads; very docile and tolerable. Not harsh, just firm, but BLOODY-WELL-DAMPED. And I like the 430/600 setup much more than the 430/550. I would strongly recommend it; its the best balance between ride-quality and performance.

In my initial thread, I merely suggested that a 525/650 would be a great entry level autocross/track setup. However, I've had the car for a week with 525/600 setup, and the front was not harsh AT ALL, however you'd feel a thud when entering a dip and short fly when going out of it AT freeway speeds. Now you know why I switched it to a 430/550 setup (during the time I wrote the initial thread). And it has now changed to 430/600.

I'm going to try out 500/650 setup. I will report back what I feel about it... However, I know that its going to "feel" much stiffer than what I have now. I am not sure how docile its going to be, but we'll see...

Of course I agree that actual testing is incredibly valuable, but one needs to start in the right ball park to make the testing effective. Butt dyno's really don't do very much for proper suspension setup.

http://buildafastercar.com/tech/Spring-Rates
http://www.rqriley.com/suspensn.htm

Those are just some quick hits that came up on Google for the natural frequency of a suspension if you are intereted.

The quick and easy estimate for spring rate is:

natural frequency = 3.13 * sqrt ( (motion ratio)^2 * (spring rate) / (corner weight))

Technically you should be using unsprung corner weight, but that approximation is generally good enough.

Of course, there are other parts in the suspension system like anti-dive/squat systems and sway bars that will change things, but sway bars will only increase your wheel rate. And then if we wanted to get the true ideal spring rate we will have to know quite a few other things like CoG, roll center, track, and motion ratio for the sway bars, etc. But generally the above formula will be a rather good approximation.

[jah29]

I really like this ground control kit. I will have to talk to GC about what "custom valved Konis" means. Hopefully 60% critically damped and then digressive… I definitely want to chose my own spring rates.

As I understand it:

1. You want the frequencies roughly the same front and rear (10% higher rear for street cars, 5% higher front for race cars.)

2. Therefore wheel rates should be the roughly the same in cars with 50% weight distribution like most BMWs.

3. Which means that difference in motion ratios F and R is the difference in spring rates. Again, Roughly.

(motion ratio f)/(motion ratio R) = .92/.32 = 2.9 rear spring rate should be around 3 times greater than the the front.

My Conclusion: Anyone who sells suspension for the current 3 and 1-series hasn't done any analysis if he's got stronger front springs than rear springs. Or maybe they've done a lot more measuring than me, and the front camber curves are so bad, super heavy springs are needed. Though I doubt BMW did that!



I think a little tweaking of this ground control kit, which they seem very willing to do, and we've got the most cost effective, high quality kit out there. Yay!!

[Orb]

Originally Posted by eltoshan

Thank you very much! I've been guessing that the rear MR to be around 0.75 or so, but I had no idea it is that low. Goes to show what actually measuring things can do.



I still don't know nearly as much about our suspension as I should, but with a different offset wheel, the amount of leverage the wheel exerts on the spring is changed, so the motion ratio would be different as well. But that would not be nearly as drastic as having longer control arms, etc.



Of course I agree that actual testing is incredibly valuable, but one needs to start in the right ball park to make the testing effective. Butt dyno's really don't do very much for proper suspension setup.

http://buildafastercar.com/tech/Spring-Rates
http://www.rqriley.com/suspensn.htm

Those are just some quick hits that came up on Google for the natural frequency of a suspension if you are intereted.

The quick and easy estimate for spring rate is:

natural frequency = 3.13 * sqrt ( (motion ratio)^2 * (spring rate) / (corner weight))

Technically you should be using unsprung corner weight, but that approximation is generally good enough.

Of course, there are other parts in the suspension system like anti-dive/squat systems and sway bars that will change things, but sway bars will only increase your wheel rate. And then if we wanted to get the true ideal spring rate we will have to know quite a few other things like CoG, roll center, track, and motion ratio for the sway bars, etc. But generally the above formula will be a rather good approximation.

It is okay to make a make a few assumptions. Say 100 lbs for the front and 135 lbs for the rear unsprung weight. Mr. 5 has my old load transfer worksheet in one of his post. The one he posted is within 3% accuracy but the M3 roll bar data is a little off but close enough. This will get you off and running.

At least you noticed the high motion ratio in the rear suspension. The question is how detrimental is this in the system? How many vendors even think of this....lets say none.

Orb

[zsapphire7]

I think custom valved means they will change the valving for each of the shocks to match your selected spring rates. This is quite important because there is probably a huge variance during manufacturing of the actual perfomance of shocks from the manufactuer. Plus depending on the strength of ur springs, youll need different dampening.

Also when doing the calculations, be sure to not forget about the sway bars... Sway bars add a lot of effective spring rate and changes depending on single rollbump vs roll situations.

Originally Posted by jah29

I really like this ground control kit. I will have to talk to GC about what "custom valved Konis" means. Hopefully 60% critically damped and then digressive… I definitely want to chose my own spring rates.

As I understand it:

1. You want the frequencies roughly the same front and rear (10% higher rear for street cars, 5% higher front for race cars.)

2. Therefore wheel rates should be the roughly the same in cars with 50% weight distribution like most BMWs.

3. Which means that difference in motion ratios F and R is the difference in spring rates. Again, Roughly.

(motion ratio f)/(motion ratio R) = .92/.32 = 2.9 rear spring rate should be around 3 times greater than the the front.

My Conclusion: Anyone who sells suspension for the current 3 and 1-series hasn't done any analysis if he's got stronger front springs than rear springs. Or maybe they've done a lot more measuring than me, and the front camber curves are so bad, super heavy springs are needed. Though I doubt BMW did that!



I think a little tweaking of this ground control kit, which they seem very willing to do, and we've got the most cost effective, high quality kit out there. Yay!!

[eltoshan]

I've always liked the few autocross cars I've driven on the street and track valved to 65-70% initial critical damping with a digressive knee at 3 in/sec. Most people I've talked to seem to feel that 65% is really the threshold where the excess motion gets a little too high below that.

Originally Posted by Orb

It is okay to make a make a few assumptions. Say 100 lbs for the front and 135 lbs for the rear unsprung weight. Mr. 5 has my old load transfer worksheet in one of his post. The one he posted is within 3% accuracy but the M3 roll bar data is a little off but close enough. This will get you off and running.

At least you noticed the high motion ratio in the rear suspension. The question is how detrimental is this in the system? How many vendors even think of this....lets say none.

Orb

Ah I'll have to look for that post. I wouldn't be surprised to see the sway bars adding a couple hundred lb/in to the wheel rate. It would be nice to go through the calculations myself, but I can't get off of my ass and measure things.

This applet should be useful in the future.

It really is a shame that in order to have a competently set up suspension system you really have to build your own. Considering that none of the major manufactures really do their homework.

[Speediance]

I'm not sure if I fully follow all the "motion ratio" talk; but I'm going to spend some time reading about it.

However, its ODD to see the following inconsistencies and contradictions.

1) From the "rough" calculations of motion ratios, if the ration of rear-spring rate to the front-spring rate is supposed to be 3, then how come some of the good suspensions like TCK (350/700) and KWCS (508/800) have ratios 2 and 1.57 respecitively. I would argue that GC (430/650) is similar to the KWCS, speaking in terms of ratios.

2) We all know that the front sway bars *a lot* stiffer than the rear ones, hence adding to the front spring rates. So the "effective" spring rate in the front should be higher, bringing the ratio close to 1.0 even more. In that case, how come a the following case is not viable where the rear spring rates are 10-20% more than the front ones. This is the case for KW V3, PSS10, and KW Clubsport (non M3).

The above data is based on: http://www.e90post.com/forums/showthread.php?t=235797

I dont know if it makes sense; like you all I'm trying to find some reason...

It'd be great if someone could UNIFY all the variables down to some simple rules-of-thumb.

[Orb]

Originally Posted by Speediance

I'm not sure if I fully follow all the "motion ratio" talk; but I'm going to spend some time reading about it.

However, its ODD to see the following inconsistencies and contradictions.

1) From the "rough" calculations of motion ratios, if the ration of rear-spring rate to the front-spring rate is supposed to be 3, then how come some of the good suspensions like TCK (350/700) and KWCS (508/800) have ratios 2 and 1.57 respecitively. I would argue that GC (430/650) is similar to the KWCS, speaking in terms of ratios.

2) We all know that the front sway bars *a lot* stiffer than the rear ones, hence adding to the front spring rates. So the "effective" spring rate in the front should be higher, bringing the ratio close to 1.0 even more. In that case, how come a the following case is not viable where the rear spring rates are 10-20% more than the front ones. This is the case for KW V3, PSS10, and KW Clubsport (non M3).

The above data is based on: http://www.e90post.com/forums/showthread.php?t=235797

I dont know if it makes sense; like you all I'm trying to find some reason...

It'd be great if someone could UNIFY all the variables down to some simple rules-of-thumb.

Hum, you more or less got things mixed up and made some very wrong/bad assumptions. You can not directly compare information you’re looking at on a scale system.

Start with basics with spring and dampers ….http://www.optimumg.com/OptimumGWebS.../TechTips.html

If you like what you have then just call it done. It is not like your setup is wrong or anything but it is not going to be the smoothest ride either. It really depends on the goal you set at the begining which is what you wanted from your setup and that what mattters..do you meet that goal?

Orb

[stressdoc]

We really need to get a few cars together for a comparison test. Wonderful that we have several experienced suspension gurus working with the E9x.