[DaFish]

Originally Posted by The HACK

I've thought about responding to this thread a long, long time ago, but refrained from doing so because I knew my time would be absolutely wasted.

I was right then.

With respect, No your not right... your time was not wasted and I really appreciated your time and it made perfect sense to me and others that want to learn. thank you.

[DaFish]

Originally Posted by The HACK

In order of effectiveness:

Tires > Alignment > Springs > Dampers > Brakes > Swaybars

I did it this way. I went with non-rfts - the pole positions. HUGE difference in grip straight line grip and wet handling.

But without the Stage 3 suspension mods (camber, springs dampers, FRONT roll bar), the tire just rolled over on the side wall and under hard cornering, I think I had slightly less cornering strength.

Once I got the dinan S3, the handling was very much improved and I don't roll over the fronts at all. There is still slight understeer at limit and I actually like that - its more confidence building and I feel I can push it harder more safely.

Next stage, Dinan rear bar (15.8mm - cost me $369 alone... rip off but I guess I am paying for the engineering and design of the WHOLE system), subframe bushings to keep things aligned and to handle the additional power, and the LSD to power out of corners and KEEP the traction as the HACK has described.

I am really looking forward to this rear end work. I am hoping the car will rotate a little more (much improved with S3) and I will be able to power out of turns (more control over throttle with the Procede) earlier.

I am going to track this year. I think I will find the oil cooler is weak and the brakes are weak.... man this is going to cost me.

[DaFish]

Originally Posted by bigdaddycane

It wasn't posted that long (long, long) ago Captain. And why did you? couldn't help yourself?

You're 3,000 miles away, yet you know exactly what is going on with MY car. Please...

Not sure why he would tell you anything anymore, I think you are being a bit harsh. Go easy man, there is no need for all that.

Originally Posted by bigdaddycane

with the KW V1s and other upgrades the car was OFF....plain and simple. There was still understeer and some odd body roll.

Can you tell me why an E90 M3 (which is similar to my car with an upgraded suspension) runs a 20mm rear sway bar? Why doesn't BMW just use the same old 13mm rear sway bar on ALL the 3 series?

The M3 sway bars and bushing have helped my car although there is a bit more Oversteer now, which I expected and would rather have than how it felt prior to the sway bar install.

M3 has different spring rates...different suspension, bushings, non-rfts, bars, subframe bushings - it is a lot different.

As the HACK said, this is like voodo to get correct. This is why I didn't bother to try - so I just paid for the engineering. FourPointDrift has described a setup in his 335 that seemed very solid -and he got very good results at the track. Check his threads out.

[bigdaddycane]

DA Fish,

My frustration with his posts have to do with someone chiming in when they have not done suspension upgrades on an E90 Sedan. I know there are general suspension principles, but this car is set up for daily driving and playing with camber and toe to maximize superior handling was not a option because I don't want to be replacing tires every 5 to 6k. Also, I did not come acrosss any sway bar bushing upgrades for the stock equipment.

My point on asking questions about the M3 was to show that when you modify the 335 suspension it is heading towards a stock M3 suspension. Your answer showed you were on the same page....I think. Going with M3 parts on a modified 335 suspension makes sense as well as other bushings and parts..

I would like to hear your review after you do this and don't do a LSD on the traction issues - if any.

I have not done the LSD yet....researching it, but I am not currently having adverse traction issues even with worn out Bridgestones on the rear. I am ordering new tires next week.

The car feels good, about the only side affect from the sways would be some increased road noise.

[qtrlifecrisis]

Originally Posted by The HACK

I've thought about responding to this thread a long, long time ago, but refrained from doing so because I knew my time would be absolutely wasted.

Time definitely not wasted, I'm listening. Thanks for the write up!

[DaFish]

Originally Posted by bigdaddycane

DA Fish,

My frustration with his posts have to do with someone chiming in when they have not done suspension upgrades on an E90 Sedan. I know there are general suspension principles, but this car is set up for daily driving and playing with camber and toe to maximize superior handling was not a option because I don't want to be replacing tires every 5 to 6k. Also, I did not come acrosss any sway bar bushing upgrades for the stock equipment.

My point on asking questions about the M3 was to show that when you modify the 335 suspension it is heading towards a stock M3 suspension. Your answer showed you were on the same page....I think. Going with M3 parts on a modified 335 suspension makes sense as well as other bushings and parts..



I have not done the LSD yet....researching it, but I am not currently having adverse traction issues even with worn out Bridgestones on the rear. I am ordering new tires next week.

The car feels good, about the only side affect from the sways would be some increased road noise.

I am a bit worried about tire wear for sure. I am running over -2 neg camber... I have to tell you though, the turn in is very nice and quick - with no adverse reactions like twitchy behaviour on high speed corners. It still understeers, but only at limit now - which is good. I hope to get the LSD in a month or so, on wait list for a core swap. Then the subframe bushings go in. I have heard lots of good things about these, and I think I can feel them now with my added power.... the rear end is squirming around and I can pass cars and turn around them without really turning my wheel. I think the rear end is shifting around - feels like it.

Did the rear sway feel much different for understeer?

I think the Dinan bar will be a subtle adjustment.

I also think the Dinan stuff is tuned to have the big front rims and tires on as well. I think if they didn't put a 9" rim, with a 255 or 265 (with camber plate) tire on the front, they would have gone with a larger rear bar... but I don't know... it is voodoo to me to.

Fun stuff though.

[chappy]

I have the m3 front 4 arms and m3 front and rear sway bars and -2 is a bit too much for the front it will wear too quick, it might have good turn in but you have to have a happy medium.

My setup is -1.39 and -1.02 front setup
-1.56 and -1.38 rear setup and its great for wear so far.
Its also got to work in conjuction with the individual toe.
So you need a balance between the two.

[bigdaddycane]

First off, for our Russian friend, here's the part numbers you requested. Sorry for the delay.

Front Bar 26.5mm
31352283515
Front Bushings
31352283516
31352283517

Rear Bar 20mm
33552283655
Rear Bushings
33552283709
33552283710

DA Fish,

If you feel that the rear is twitchy it probably is. That is what I was feeling as well.

Did the rear sway feel much different for understeer?

Yes, most of the understeer is gone.

Dinan usually uses other companies parts especially for the suspension. It would be curious if someone knew who's parts (if they were) using. If that is the case you could get the parts cheaper elsewhere.

Larger front tires definitely changes the suspension dynamic. I'm sure that's why they can run smaller bars (especially in the rear).

[31 Hz]

There is a ton of information in Hack's posts. Thanks, dood.

[mythek]

Originally Posted by The HACK

I do.



I've said this before and I'll say it one more time.

In the world of suspension tuning, swaybars offer the LEAST amount of gain for the money. In order of effectiveness:

Tires > Alignment > Springs > Dampers > Brakes > Swaybars

And the tricky part of the whole equation is, swaybars are the ONLY component on the list that take away grip. Swaybars in essence, lock the two sides of the suspension and prevent it from moving independently, thus reducing overall grip of the system. While this is a gross simplification of the theory of grip, it is also all but universal (I'll get to the "but" part later).

Tires, of course, offer the biggest improvement on grip and handling because it's the ONLY thing coming in contact with the road. Obviously grippier the tire, the more traction/grip you have, the better the car handles. Alignment, or proper alignment, allows the tires to stay in contact with the ground during cornering. Springs, or the energy stored in the springs, keeps the tire in contact with the ground as the weight of the vehicle moves from one side to another in a dynamic state. Dampers control the movement of the springs therefore controls the rate that springs put force onto the tires to keep it on the ground. Brakes, while technically not part of the system, allows you to transfer weight from one end to the other, thus increase the grip on the front end when you use it.

Swaybar, on the other hand, prevents the springs from transmitting that force to the tires to keep it on the ground, therefore thicker swaybars actually take away grip. That's why, if you look at a general "handling" chart, it is almost always recommended to "stiffen" up the OPPOSITE axle to cure understeer or oversteer. It balances the car out by removing grip on the end that has it so both sides lose grip at the same rate.

So the effect of adding bigger swaybars will result in a SLOWER lap time because you simply won't have the same amount of grip through the turns. Typically, racers and successful autocrossers will use swaybar upgrades as the LAST thing to fine-tune the balance of the car. In fact there are multiple successful national club racers and autocrossers who will run without bars either up front or in the rear to achieve a more balanced chassis.

HAVING SAID ALL THAT.

Swaybars are not without merit. Since BMW needs to build street cars that appeal to the masses, rather than race cars, they needed to provide a relatively soft suspension with soft springs and light dampers. The end result of trying to achieve moderate street comfort is significant body roll in corners. The best compromise, is to take away a moderately small amount of grip, and use swaybars to decrease the side to side motion known as "roll". This way the car will retain relative civility going straight, while giving up little grip for the sensation that it's "cornering on rails."

It's all a relative compromise. Since grippier tires with stiff sidewalls, or stiffer springs, or high rebound/compression dampers will affect ride comfort at all times, going straight or in a turn, for a street car it is not uncommon to NOT equip it with very stiff springs but use swaybars to compensate. So, for a street driven only car, it is actually not a bad idea to upgrade only the swaybars since you sacrifice none of the straight line comfort, while only giving up some moderate grip, which you will get some back by the swaybars acting as increased wheel rate through corners (the torsional stiffness of the swaybars ADD wheel rate to the outside wheel) plus it'll keep the body-roll to a minimum to create the added illusion that the car is "handling" well, as long as it's not being pushed to its traction limit (since cars with upgraded swaybars will have lower traction limit).

So, as long as you understand how swaybars work and its limitations, upgrading swaybars for a mostly street driven car actually has a lot of benefits and very little drawback. But from a standpoint of real performance applications, adding swaybars for "performance" is a bit of an oxymoron. At least, for performance, I'd add better tires, proper alignment, better springs/shocks, and maybe even better brakes before I move on to swaybars.

Originally Posted by The HACK

Don't know. Depending on when, where, and how the understeer is occurring, and if it really is understeer.

I'm going to let you in on a little secret. It may sound like I know what I'm talking about. I may even ACT like I know what I'm talking about. But when it comes to suspension tuning? It is a freakin' VOODOO art that I haven't even come close to scratching the surface.

The god awful truth is, every single components I listed above, tires, alignment, springs, shocks, brake, and sways all work as a system with multiple variables that makes outcome UNPREDICTABLE. Remember in my earlier post I mentioned the "but" part of "all but universal?"

I remember, long long time ago, back long before I became the "guru" that I am, I had a guy show me that by stiffening up the front swaybars (I had adjustable sways) I could actually potentially eliminate the UNDERSTEER that I was experiencing through a specific turn. I was shocked. I mean, I was holding onto the bible that says "to cure understeer, stiffen the rear sway. To cure oversteer, stiffen the front sway (hence stiffen the opposite axle of the end that lose grip first)." I was baffled as to why that is so, until my friend (god rest his soul. He was taken away from us and the community way too early) showed me that with the amount of camber I had, actually stiffening the swaybar resulted in limiting the front suspension's movement enough that it prevented the OUTSIDE front from compressing past the roll center, therefore keeping my camber in a favorable state through that combination of turns.

At that time I was absolutely floored. He gave me the bible about tires > alignment > springs > shocks...etc. But even he said, none of this means anything. Your goal is to maximize the amount of grip to each end, then decrease the end that has more available maximum grip so both ends are even. How you go about doing it, is by testing. Your tire's grip may be static, but the alignment setting will determine how to maximize that grip. Then your springs will determine how long that grip is available to you in a corner. Then your dampers will extend that available grip. Blah blah blah. But each one of these settings will have an effect one way or another, and while you increase your grip level in one way, you may in effect be decreasing that grip in a different state. Again I was floored. In the end, what I learned from my friend was, the only way to know for sure, is try out different settings starting with the tire (tire pressure). Once you achieved maximum grip there for that specific tire, you move on to alignment. Then you measure temperature across tires to see if it's even and adjust accordingly. Then you use stiffer springs, and adjust the dampers to control those springs until you get ideal results based on your lap time, then you learn to use your brakes to effectively manage weight transfer to improve that lap time, then if you're suffering understeer or oversteer in a specific corner or series of corners despite your adjusting of your driving, you can use adjustable swaybars to dial in or out of understeer...But just be aware that the effect may not always be as desired, and that's where TESTING is going to help you.

So why am I telling you all this? It is irrelevant. Typically, oversteer or understeer state can be resolved LONG before you get to needing to adjust swaybars. And even *I* don't go beyond adjusting a few lbs of pressure here or there or add a little bit more camber up front, because true effect on understeer and oversteer are magnitudes larger there. And in reality, those that actually do understand how this stuff works, have spent decades working on racecars and wouldn't bother to spend that much time posting on an intarweb forum.

Anyway, to answer your question.

In general, the stiffer the swaybar, the less grip is available...Or the LIMIT of grip is lowered. Meaning, again, in general, if you're experiencing UNDERSTEER you need to stiffen the rear bar. If you're experiencing OVERSTEER you need to stiffen the front bar.

Unfortunately, that general rule doesn't always work outside of steady state understeer in a skidpad condition. When understeer occurs at corner entry SOMETIMES it may actually resolve the problem by stiffening up the front. While this is counter-intuitive, it goes back to the unfavorable camber curves of the MacPherson Strut up front. By locking the front suspension from moving independently, a thicker bar up front may actually improve front end grip if the car has ample camber up front already. BUT. In that same scenario, a TOO STIFF bar may actually lift the inside front tire therefore decreasing grip.

That is why, for a street car driven on the street, swaybars are great. It gives you the illusion of less body-roll without sacrificing ride comfort. For the track? I leave mine alone. Or at least get marginally larger bars that I can adjust to my heart's content.

But if I'm getting bars for street use only? It matters very little whether it increases or decreases understeer, really.

So if you're still not confused enough to still think clearly, what I'm saying is, if you're not going to the track, it doesn't matter.

Originally Posted by The HACK

I've thought about responding to this thread a long, long time ago, but refrained from doing so because I knew my time would be absolutely wasted.

I was right then.

If you upgrade your springs and shocks you don't need to upgrade your swaybar. The effect on the car's actual ability to provide grip is decreased when you upgrade your swaybar. Upgrading swaybar is for when you don't want to lose street comfort, don't drive past the traction limit enough times to know where it's at, and want to reduce body roll to make it easier to control the vehicle at the lower half of the car's capability to corner.

By upgrading the suspension all around with springs and shocks, then "upgrading" the swaybar actually decreases your car's ability to go through corner at speed.

Originally Posted by bigdaddycane

A little background on my car:
I had previously install KW V1 coilovers on my 07 335 and really liked the setup. But the more I drove the car I realized that something was off.; nothing major, but the car was twitchy and I attributed it to the very small rear sway bar. The 335 comes with a 26.5 mm front sway bar and a 13mm rear. The oem rear sway bar can be mistaken for a brake line; it’s tiny! I’ve seen Honda Accords with bigger rear sway bars!

Anyway, I did some research and the aftermarket sway bars (Hotchkis and H&R) are really expensive so I started looking at the oem M3 sways. The M3 has a 26.5mm front sway bar and a 20mm rear sway bar. Those sizes are very close to the aftermarket sway bar kits. The bushings are also much stiffer than the stock 335 sway bar bushings due to their makeup which is rubber coated steel bearings. The front and rear sway bars, bushings and clamps run ~$310 before shipping from Faulkner BMW in Pa. Most aftermarket kits are near $400 or more. Part numbers can be found on realoem.com. I can post them here if anyone is interested as well.

Also, the E90 M3 Convertible runs a 23.5 rear bar, but I did not want to go this extreme as I wanted to keep the car balanced. I noted this for anyone who is looking for something more extreme. The cost is the same as the non-convertible rear sway bar.

Now to the install:
We tackled this at my buddy Jon's fully outfitted garage Saturday. The front bar is very straightforward and does not take much time (approx 45 mins). Why change the front when they are the same size you ask? Well, the stock 335 front sway bar has a taper in two spots and the M3 sway does not. The taper affects the bar’s affective rate. Also, the M3 bushings are rubber coated steel bearings, not just rubber bushings like the 335 bar uses.

The rear sway bar is a giant m*thaf*ker. Basically you have to lower the entire rear subframe and exhaust to make room to fish the bigger M3 sway bar into place. Probably took 2.5 hours to do but could be done faster now because of lessons learned. Basically, any suspension work in the rear of the 335 is a PITA.
Fitment for front and rear is perfect.

Driving impressions:
Wow! Much better, this is the way the car should have come from the factory. Huge improvement in the rear and the understeer is minimized. 7mm makes a noticeable difference. There is a bit more “road noise” but nothing that could be considered annoying.

Overall, I’m really happy with this upgrade even though the (rear) install was draining.

Here are some comparison pictures of the stock 335 rear sway bar and the stock M3 sway bar that replaced it.





Part numbers used:

Front Bar
31352283515
Front Bushings
31352283516
31352283517

Rear Bar
33552283655
Rear Bushings
33552283709
33552283710

Thank you Hack for that very informative post in regarding to fine tuning suspension. I actually was going upgrade swaybar and came across this thread as i'm trying to do my homework. I certainly hope members with technical knowledge will continue to contribute to the community.

and also thank you OP for taking the time to post your review and part numbers to help those interested in swaybar upgrades. I'm sure everyone has a different purpose for their car, so i don't think swaybar is a wrong or wasteful upgrade.