Question on adding front sway

[bodega_bladerunner]

So I've recently had a bunch of suspension work done on a new to me 2013 I have now had for a few months. It's a replacement 135 for a totaled one from last year.
The work I had done was:
Front m3 arms
White line subframe bushings (the full ones, not the little inserts)
Bilstein b14 coilovers
Dinan camber plates

From stock, the car is now night and day. It handles so well now that is brings a tear to my eye. However, now that I've been on this new set up for almost a month, I've gotten used to it and feel something small is missing or needs upgrading. Like I can feel the body roll at lower speeds, which disappears are higher 20-60mph speeds when (I'm guessing) the improved suspension kicks in.

That is where my curiosity about a front sway comes in. Right now, the car handles very well with a neutral feeling front to back. How much would adding a stiff h&r front sway upset that neutral feel? I don't want to lose that.

Thanks all

[bbnks2]

Originally Posted by greenc51

So I've recently had a bunch of suspension work done on a new to me 2013 I have now had for a few months. It's a replacement 135 for a totaled one from last year.
The work I had done was:
Front m3 arms
White line subframe bushings (the full ones, not the little inserts)
Bilstein b14 coilovers
Dinan camber plates

From stock, the car is now night and day. It handles so well now that is brings a tear to my eye. However, now that I've been on this new set up for almost a month, I've gotten used to it and feel something small is missing or needs upgrading. Like I can feel the body roll at lower speeds, which disappears are higher 20-60mph speeds when (I'm guessing) the improved suspension kicks in.

That is where my curiosity about a front sway comes in. Right now, the car handles very well with a neutral feeling front to back. How much would adding a stiff h&r front sway upset that neutral feel? I don't want to lose that.

Thanks all

Aftermarket sway bars (solid) are MASSIVELY stiffer than stock (hollow). You will probably upset the neutral balance unless you upgrade the rear sway as well!

Alternatively, you can upgrade your suspension to something a bit stiffer. Something like 4k/12k is 2x stiffer than stock, but it is still very comfortable for daily driving. You can google the trade-offs between tuning sway bars vs tuning spring rates tuning at your own leisure.

[bodega_bladerunner]

Originally Posted by bbnks2

Aftermarket sway bars (solid) are MASSIVELY stiffer than stock (hollow). You will probably upset the neutral balance unless you upgrade the rear sway as well!

Alternatively, you can upgrade your suspension to something a bit stiffer. Something like 4k/12k is 2x stiffer than stock, but it is still very comfortable for daily driving. You can google the trade-offs between tuning sway bars vs tuning spring rates tuning at your own leisure.

Interesting that you say that because after I posted this thread, I kept finding on the forums that adding a front sway alone actually helped with decreasing understeer on these cars. But I also read threads that advised adding both front and rear. So that's where I'm confused...the conflicting threads

[bNks334]

Originally Posted by greenc51

Interesting that you say that because after I posted this thread, I kept finding on the forums that adding a front sway alone actually helped with decreasing understeer on these cars. But I also read threads that advised adding both front and rear. So that's where I'm confused...the conflicting threads

Your m3 control arms and Dinan camber plates allow you to dial in enough negative camber (at least -1.7*) which will offset any dynamic camber change that occurs under braking/compression due to the McPherson front suspension design... if you didn't have the extra negative camber a sway bar could be used to stiffen roll resistance to achieve the samw goal of reducing the amount of camber loss instead of offseating it with static negative camber.

Both ways allow the car to corner flatter but doing both co.bind can be overkill and cause the car to push.

Are your tires rolling over onto their sidewalls? If so, try bumping psi up a few psi. Still rolling over onto the tires shoulder excessively? Time to increase roll resistance with bigger F & R sway bars or stiffer spring rates... or more negative camber (past -2.5 isn't advised).

[bodega_bladerunner]

This is my alignment setup

[iminhell1]

Body roll is not always a bad thing and I would not upgrade anything right now until you get some track numbers to go by. Do some HPDE or Autocross. Gather data. Adjust alignment and retest.
If you don't find an alignment setting that gets you as fast as you want to be, then try upgrading a sway. And retest again.


The entire point of suspension is articulation and independent movement. Swaybars limit both. People assume that body roll is a bad thing but sometimes (most actually) it's not. Because of the McPherson setup (flawed) you have to achieve X" of compression to achieve Y* of dynamic camber to keep tire deflection from pulling contact patch off the surface. The brand of tire, the speed of the turn, the race surface, etc., etc can all play part in what changes need to be made to achieve maximum grip. Sometimes even letting more weight transfer to an outside tire will add to the grip, that is what body roll does.


The car and setup is brand new to you. Don't jump on a bandwagon just because it is. Do so because you've tested and can prove that is what you need to do.



I have yet to see anyone post a dynamic alignment chart for these cars and I highly suspect that on a lowered car adding negative camber is going to put more load on the outside tire because the inside can't reach a neutral grip plane.

[John_01]

I think the H&R front sway bar will be too much for your setup with Eibach springs.

A Firm front sway bar will increase the weight transfer to the outside front wheel. When the load transfer is too much and too rapid, it places extra stress on the loaded tire which can result in less grip. It means it will promote understeer at the limit of grip. The advantage of softer springs or softer front sway bar is more gradual loading of the outside tire.

It is necessary to strike a balance of stiffness between front and rear. That's why I think the 27mm solid H&R front bar will be too much and may upset the balance. Alternatively for a smaller increase in stiffness you could consider a M3 front sway bar instead of the H&R - either E93 M3 or E92 M3 front bars. That will be a smaller change and the handling, and I think the overall handling balance will remain similar to what you have now. The sway bar can actually make the steering feel a bit more responsive. An increase in sway bar stiffness can reduce under steer if it allows the car to roll less and maintain more front tire contact area on the track. There will be an optimum setup somewhere.

Just like the above poster, I suggest to try the car on the track as it is now, then make changes later. Then you can become more aware about how much difference occurred and whether you like it or not.

[tsk94]

If your car is neutral with it's current setup, adding a stiffer front bar (while doing nothing to the back) will result in understeer at the limit.

Also, some body roll definitely isn't a bad thing.

My advice would be:
A. Do neither, leave it as is. You say the balance is neutral so why mess with things.
B. Do Front AND Rear bar. That way you keep the handling balance neutral, while getting rid of some of the body roll.

[HP Autosport]

Originally Posted by John_01

I think the H&R front sway bar will be too much for your setup with Eibach springs.

A Firm front sway bar will increase the weight transfer to the outside front wheel. When the load transfer is too much and too rapid, it places extra stress on the loaded tire which can result in less grip. It means it will promote understeer at the limit of grip. The advantage of softer springs or softer front sway bar is more gradual loading of the outside tire.

It is necessary to strike a balance of stiffness between front and rear. That's why I think the 27mm solid H&R front bar will be too much and may upset the balance. Alternatively for a smaller increase in stiffness you could consider a M3 front sway bar instead of the H&R - either E93 M3 or E92 M3 front bars. That will be a smaller change and the handling, and I think the overall handling balance will remain similar to what you have now. The sway bar can actually make the steering feel a bit more responsive. An increase in sway bar stiffness can reduce under steer if it allows the car to roll less and maintain more front tire contact area on the track. There will be an optimum setup somewhere.

Just like the above poster, I suggest to try the car on the track as it is now, then make changes later. Then you can become more aware about how much difference occurred and whether you like it or not.

My vote is on the E9x M3 bar as well. H&R front only will be too stiff and will upset the balance you currently have.

[bodega_bladerunner]

thanks for the feedback everyone. Do you all think the e93 bar would be a better choice? Also, anyone know if there is an aftermarket equivalent? Only asking because I know the bmw m3 sways are a pretty penny, and I'm sure a reputable aftermarket manufacture makes something similar for less $

[EndOfAnEra]

Just want to chime in here.

I installed a E93 M3 28mm fsb last week. It definitely tightens up the car around corners. It was not a huge difference, but that's why I went with larger OEM rather than aftermarket. Hope that helps.

[deesea]

Originally Posted by EndOfAnEra

Just want to chime in here.

I installed a E93 M3 28mm fsb last week. It definitely tightens up the car around corners. It was not a huge difference, but that's why I went with larger OEM rather than aftermarket. Hope that helps.

Curious to know what your suspension settings/mods are? Looking at your build I'm not seeing any mention of suspension work - I believe people earlier already mentioned that on a stock suspension, the M3 FSB makes a big difference to driving feel.

Have you had any changes to your suspension settings?

[Gangplank]

Originally Posted by greenc51

thanks for the feedback everyone. Do you all think the e93 bar would be a better choice? Also, anyone know if there is an aftermarket equivalent? Only asking because I know the bmw m3 sways are a pretty penny, and I'm sure a reputable aftermarket manufacture makes something similar for less $

[IMG]https://1c2a8a2161d644d95009-22d26b3...comparison.jpg[/IMG]

The e92/e93 sway bars aren't all that expensive. I've seen the for about $225