[karapet85]

Originally Posted by johnung

No, the point wasn’t to stay away from H&R Sway Bars. H&R has made super high quality solid steel sway bars for many decades. They make a great front bar for the F3x. The design for their sway bar kits wasn’t great because their 20mm rear bar that is too thick for this chassis under certain road conditions.

ISSUE WITH HEAVY 20mm REAR SWAY BAR
Namely under very high speed cornering, and especially if you hit a rough patch of road, the H&R 20mm rear bar is so strong that it can cause lift in one wheel which reduces the contact patch of that tire.

I’ve been driving my daily for years with the H&R F28/R20mm sway bar kit. It’s really difficult to find/create this negative condition on the street. It would be more obvious at track speeds. Nevertheless when I do a suspension refresh, I am going to clean it up a bit by downsizing my rear sway bar from the H&R 20mm to the KC Design 17mm rear sway bar.

F3x HAS (4) DIFFERENT FRONT SWAY BAR SHAPES
What many people do not realize, including retailers who sell sway bars, is that for the F3x there are typically four different front sway bar shapes. This is because engines/suspensions in the front of the car differ depending on small/large engine and RWD/XDrive drivetrain configuration.

There’s only one rear sway bar shape because in the rear all of these cars are pretty much the same. Most of the variation happens in the front.

CHOOSING SWAY BARS IS DIFFICULT
IMO there are much bigger limitations to choosing F3x sway bars for a particular car than most people suspect for four reasons:

1) The manufacturer does not make sway [...]

Thanks, johnung
I always thought that it is better to change the sway bars in pair, e.g. that the kit is a better solution to avoid any safety risks that different sway bars may arrise.
I guess i was wrong.

[johnung]

I used to advocate changing sway bars in kits from the same manufacturer because the assumption was that they actually did a lot of testing with different sized front and rear bars to determine the best front/rear match for the chassis. But I don’t think that that is necessarily the case now. From my research the shared information indicates that it’s better to choose from the best front and rear sway bars for the car application.

[karapet85]

johnung
Thank you. Real usage feedback is very important to me. You also covered the theoretical part. I used to think that hollow bars are good ( I bet many others too ).

At this point, I will wait for my EPK and decide what to do next. H&R for the front and KC for the rear is my favorite for now, but I will do more research before taking any actions. It is a bit strange that KC is not manufacturing/selling the fronts too.

Another company selling a sway bar kit is Dinan, but their sway bars are hollow too.

[johnung]

Originally Posted by karapet85

johnung
Thank you. Real usage feedback is very important to me. You also covered the theoretical part. I used to think that hollow bars are good ( I bet many others too ).

At this point, I will wait for my EPK and decide what to do next. H&R for the front and KC for the rear is my favorite for now, but I will do more research before taking any actions. It is a bit strange that KC is not manufacturing/selling the fronts too.

Another company selling a sway bar kit is Dinan, but their sway bars are hollow too.

Yeah, I used to think maybe hollow bars were more modern, high tech, etc. but the more research that I did changed my mind, I don’t think that now, especially for the consumer market.

Race teams have engineers who can use hollow bars to cut weight while making sure that tubing thickness and shape is strong and safe for the track. On the consumer side it’s too little engineering, mostly cost cutting and a bunch of slick marketing to gloss things up. Once I started seeing photos of snapped hollow bars I realized that there’s a reason that a company like H&R still makes and sells solid steel bars. I’ve been using there sway bars for many decades. Old VW GTI’s had easy sway bar access so it was really simple to play around suspension tweaking by swapping in a smaller/larger front or rear sway. Track guys would do it to setup their car for specific tracks. The H&R solid bars were so consistently well made, reliable and safe. Great German engineering.

KC Design actually used to have a 28mm solid front bar for a RWD model. I don’t see it in their catalog now. Once I saw the KC sways next to the H&R sway bars. They were very similar, almost identical. That’s why I have complete confidence swapping out my 20mm rear H&R bar for a 17mm KC model.

In my previous conversations with KC, they said that they do their product development by bringing in a car for their engineers to work from. Well it turns out that BMW doesn’t sell XDrive cars in Taiwan. I’m guessing that might be the case for most of Asia. So that’s why they never made XDrive front sway bars.

[karapet85]

johnung Thank you, much appreciated.

[casualDIYer]

Originally Posted by johnung

A common mistake that guys make too is to lower the car but not replace/modify the stock bump stops. The bump stops are a high tech way of cushioning before a damper actually would bottom out. So it's like a secondary damper. Read posts from FaRKle! on this subject.

If a car is lowered but the stock bump stops are left then the car could be prematurely bottoming out on the stock bump stops causing what appears to be a rough ride. A good solution is often to replace the stock bump stops with shorter F80 bump stops. See photo.

Hope this helps!

@johnung is correct. I've made this mistake for which the penalty is crashy suspension on bumpy streets. While suspension work isn't difficult in terms of mechanical complexity, it is pain in the a$$ to take things apart, replace the bump stop, put it back together.

My route to learning about bump stops on on ACS springs + Koni Yellow Sport Dampers. Car is 2017 340 xDrive

OE bumpstops = crashy over any bump bigger than a pebble

F80 (front and rear) bumpstops = better but still crashy over medium or larger bumps

Dinan (front) + F80 (rear) bumpstops = a lot better. You've got to hunt for a bump and hit it hard to ride those bump stops.

Why the F80 bump stops in the rear and not the Dinan? The hole in which the damper piston rod runs through is too narrow on the Dinan bump stop to accommodate the Koni Yellow damper piston. Plus, the Dinan rear bump stops are too short to protect the piston. The F80 was a better match.

[casualDIYer]

Originally Posted by opvaulet

Hi, how are the Koni sport working for you? What settings do you have on them? I am considering them but looking for feedback. So few people choose these Koni’s.

Thanks much!

Sorry everyone, this is a little off topic. I'll make it brief.

CRITICAL: I couldn't find any setting with the Koni Sport dampers that would eliminate crashiness over ever average sized bumps when using RUN-FLAT tires. Highly suggest use of NON-RFT tires

I have the Koni Sport (i.e. yellow) dampers paired with ACS springs (which are friggn' fantastic by the way).
This is what I have learned over the last year of using them.

For the rear, 2/3 from full soft (i.e. fastest reaction setting)

For the STREET, for the front, 3/4 from full soft. This WILL introduce some bounciness but is a better choice than teeth smashing hell on higher settings

For the TRACK, for the front, 1 1/2 turns from full soft. Roll is minimal. If you have the time, set the rear to 1 full turn from full soft.

Dislikes:
Wish I could keep the softer settings without the bounciness.

Likes:
I have the flexibility to change the settings.
For an adjustable damper, the Koni Sport is decently priced.

Tip: You can read every internet post out there but trying the settings yourself are going to be the best teacher.

[rlesko]

First of all thanks SOO much to the many members who have provided invaluable information on this thread so far.

I've gone down a huge suspension rabbit hole researching how to responsibly give my car a modest drop, found this thread. How this relates to ARBs? Well, I was looking at the M Performance Suspension Kit (33502320981 pre LCI 335i kit) which indicates that its only compatible with cars that have the M Sport Suspension. Looking at the table of chassis and bar thickness, I don't understand why the M sport suspension is necessary to put the M Performance Suspension on a 335i (pre LCI)?

From what I can see, the M sport front is 1 mm thicker in the middle, but equivalent on the ends (25/22.2 vs 25/21.2). The rear is 1mm thicker.

Can someone explain why the M performance Suspension would be incompatible with stock 335i ARBs?

Furthermore, would the M Performance Suspension work with different aftermarket ARBs and/or the recommended 15 mm m2xx rear bar?

[SuperLomi]

It’s not strictly speaking incompatible.

Just that the package was intended for use with the bigger bar. Nothing is stopping you from running it as is, or from using aftermarket bars (in fact from a performance perspective an aftermarket bar would be better if you are going to go through the trouble of swapping, IMO).

You’ll have a bit more body roll, and the car will feel a bit softer during cornering without it.

Plenty of people have put on stiffer suspensions without changing roll bars. It may not be optimal, but it’s still serviceable. If you can’t afford it now, I can be done down the line if you feel you need it.

[rlesko]

Originally Posted by SuperLomi

It’s not strictly speaking incompatible.

Just that the package was intended for use with the bigger bar. Nothing is stopping you from running it as is, or from using aftermarket bars (in fact from a performance perspective an aftermarket bar would be better if you are going to go through the trouble of swapping, IMO).

You’ll have a bit more body roll, and the car will feel a bit softer during cornering without it.

Plenty of people have put on stiffer suspensions without changing roll bars. It may not be optimal, but it’s still serviceable. If you can’t afford it now, I can be done down the line if you feel you need it.

This is exactly what I was wondering about, thank you! I was not about to drop the subframe for a 1mm different in the middle of the bar only.

[johnung]

Originally Posted by Lancelot

I've put together a table of the available ARBs for our platform, BMW has quite a lot of options depending on engine, suspension, M Sport, M Adaptive or standard.

In a nutshell:
- 6 cyl get weaker front bars than 4 cyl engines
- M Sport has slightly stronger bars front and rear
- 440i LCI have stronger bars (same as M235i) than non-LCI 435i
- Xdrive have weaker front bars but same rear bars.

Aftermarket:
I've tried the H&R but they're too stiff on the rear.
I've now put on the M235i bars now and they're too weak on the front.
The sweet spot is probably the KW or Eibach, which I might try next.
(I always put bars in pairs because they're designed as pairs)

Some vendors (Hotchkis, Dinan) have hollow bars so you can't directly compare diameters with plain, non-hollow bars, hollow bar will be weaker than plain for same outer diameter.

Hope this helps...

Hello,
Are you still updating this sway bar list? (It’s very helpful) Or is someone else? I have some corrections and additions and want to send them to the correct person. Thanks!
John

[Watsey]

Originally Posted by johnung

Hello,
Are you still updating this sway bar list? (It’s very helpful) Or is someone else? I have some corrections and additions and want to send them to the correct person. Thanks!
John

AFAIK Lancelot no longer has a BMW so I assume he’s not updating the table.

If you PM him he may be able to send the table to you.

[rlesko]

Originally Posted by johnung

Hello,
Are you still updating this sway bar list? (It’s very helpful) Or is someone else? I have some corrections and additions and want to send them to the correct person. Thanks!
John

John, why don't you share your findings anyways?

[johnung]

Originally Posted by rlesko

John, why don't you share your findings anyways?

I’ve already shared it in pieces in multiple posts. I’m just too busy to take the time to pull it all together and then type it twice. Rather have the original spreadsheet to work on.

[johnung]

Originally Posted by Lancelot

I've put together a table of the available ARBs for our platform, BMW has quite a lot of options depending on engine, suspension, M Sport, M Adaptive or standard.

In a nutshell:
- 6 cyl get weaker front bars than 4 cyl engines
- M Sport has slightly stronger bars front and rear
- 440i LCI have stronger bars (same as M235i) than non-LCI 435i
- Xdrive have weaker front bars but same rear bars.

Aftermarket:
I've tried the H&R but they're too stiff on the rear.
I've now put on the M235i bars now and they're too weak on the front.
The sweet spot is probably the KW or Eibach, which I might try next.
(I always put bars in pairs because they're designed as pairs)

Some vendors (Hotchkis, Dinan) have hollow bars so you can't directly compare diameters with plain, non-hollow bars, hollow bar will be weaker than plain for same outer diameter.

Hope this helps...

DOES ANYONE HAVE THE SPREADSHEET FROM THIS ORIGINAL POST SO THAT IT CAN BE UPDATED?

CAN SOMEONE PLEASE FORWARD THIS REQUEST TO THE ADMINS OF BIMMERPOST TO SEE IF THEY CAN ASSIST?

THANKS!
JohnU

[mixmastermike]

Originally Posted by johnung

No, the point wasn’t to stay away from H&R Sway Bars. H&R has made super high quality solid steel sway bars for many decades. They make a great front bar for the F3x. The design for their sway bar kits wasn’t great because their 20mm rear bar that is too thick for this chassis under certain road conditions.

ISSUE WITH HEAVY 20mm REAR SWAY BAR
Namely under very high speed cornering, and especially if you hit a rough patch of road, the H&R 20mm rear bar is so strong that it can cause lift in one wheel which reduces the contact patch of that tire.

I’ve been driving my daily for years with the H&R F28/R20mm sway bar kit. It’s really difficult to find/create this negative condition on the street. It would be more obvious at track speeds. Nevertheless when I do a suspension refresh, I am going to clean it up a bit by downsizing my rear sway bar from the H&R 20mm to the KC Design 17mm rear sway bar.

F3x HAS (4) DIFFERENT FRONT SWAY BAR SHAPES
What many people do not realize, including retailers who sell sway bars, is that for the F3x there are typically four different front sway bar shapes. This is because engines/suspensions in the front of the car differ depending on small/large engine and RWD/XDrive drivetrain configuration.

There’s only one rear sway bar shape because in the rear all of these cars are pretty much the same. Most of the variation happens in the front.

CHOOSING SWAY BARS IS DIFFICULT
IMO there are much bigger limitations to choosing F3x sway bars for a particular car than most people suspect for four reasons:

1) The manufacturer does not make sway bars in all four F3x front configurations. (Remember that pretty much all rear bars fit. The selection issues almost always involve the front bar.)

For example…Happens all the time that someone with a different car, say a 6-cyl RWD recommends a YYY brand sway bar kit. But you’ve got say a 4-cyl XDrive and YYY doesn’t make a sway bar kit to fit it. Or worse you buy it and only find out that it doesn’t fit your car during the installation.

2) The bar sizing in the manufacturers sway bar kit is undesirable.

For example…This is the case with F3x H&R kits that include the 20mm rear bar that’s too thick for the reason discussed above. Luckily H&R sells their front & rear bars individually, so it’s easy to install the H&R front bar along with a different thinner rear bar under 20mm. (Most stock rear bars are 12mm or less.)

3) The manufacturer only sells their sway bars in kits.

For example…One of the bars in their kit would work for you, but they won’t sell you just the single bar, they force you to buy both.

4) One or both bars in a sway bar kit is hollow tubing, rather than solid steel. Manufacturers add marketing spin that hollow bars are just as strong and also save weight. The truth is that manufacturers choose hollow bars because they are more profitable. They are cheap! Solid bars use more steel so they are more expensive to manufacture. Also hollow bars are much more prone to failure. There are photos posted showing hollow sway bars that have suddenly snapped under stress/load.

For example…different car & part but same concept, I had a friend who was just driving down the highway at 50mg. Suddenly a front suspension component snapped and threw his car sideways into a concrete barrier. He died from his injuries. That’s why I never play the odds with automotive safety components like suspension, tires, brakes, etc. Never worth any risk at all to myself, family/friends lives, or lives of other drivers or pedestrians.

H&R SELLS ALL F3x FRONT BAR SHAPES
All H&R sway bars are high quality, solid steel, and they manufacture all four shapes for the front sway bar on the many F3x models. Below are the H&R part numbers for the individual Front solid 28mm sway bar.

H&R# BMW F3x Model
70878-5 4-Cylinder RWD
70878-6 4-Cylinder XDrive
70878-2 6-Cylinder RWD
70878-3 6-Cylinder XDrive

H&R REAR SWAY BAR
The rear solid 20mm H&R sway bar is H&R part number is 71878. It’s not desirable for the F3x for reasons stated above. I have heard of one excellent application for this thick rear bar. The Bilstein B16 coilover kit uses overly high spring rate springs in the front so it’s best to leave the stock front sway bar. But the rear can really benefit from this 20mm bar.

SWAY BARS ELIMINATE CHASSIS BODY ROLL
Note: There’s a misconception that thicker sway bars cause stiffer ride. Basically not true. When driving straight down a highway, sway bars are doing pretty much nothing. It’s when a car is thrown into a corner that sway bars act like left/right levers to help to prevent body roll. My car feels like any other F30 driving down the road, but accelerate into a high speed curve and it stays close to flat!

CHOOSING A REAR SWAY BAR
It’s easy to buy the correct front solid H&R 28mm bar from the part# table listed above. There are three good choices for a solid rear F3x sway bar to match with it. Remember that most stock rear bars are 12mm in diameter or less. So any of these would be a great match without getting to that 20mm rear bar thickness that is less than desirable in very specific situations detailed above.

1) 15mm Solid BMW Rear Sway Bar
Part numbers/details can be found in the attached photo. Can be purchased at a local dealer, at a discount from GetBMWParts website, or from other retailers.

2) 16mm Solid Eibach Rear Sway Bar
Don’t be fooled when you see that the Eibach Sway Bar Kit has F28mm/R16mm bars. The Eibach front bar is hollow and Eibach does not make all four front bar shapes. Eibach retailers especially in the US, mostly only sell kits with both bars. I did see the Eibach solid 16mm rear bar available for purchase once. If I find it in my notes, I’ll update this post.

3) 17mm solid KC Design rear sway bar
KC Design Part# KC-SB17-BM005
Link to product
https://www.tw-kcdesign.com/products_detail/91

KC Design is a high quality engineering, design and manufacturing company located in Taiwan. They accept PayPal. Prices are reasonable but there is an air freight shipping cost which they will quote from high end shipping companies like FedEx and DHL. Pricing varies by US zip so a little cheaper to west coast than east coast. They’ve quoted to expect 5-10 days shipping but my most recent order took only 2-3 days by FedEx from Taiwan to my door on the east coast. Amazing.

INSTALLING F3x SWAY BARS
Installation of sway bars on the F3x chassis is labor expensive because it takes a long time to remove the parts that are in the way that are burying the stock sway bars. Not difficult, just time consuming. And some things go faster with two people.

Dealers especially quote ridiculous numbers of labor hours because the dealers who do Dinan installs have inflated labor hour numbers from Dinan designed to enrich dealer service groups to motivate them to sell Dinan parts. Avoid Dinan sways which are hollow.

FaRKle! made some excellent videos which I’ll post links to below.

FRONT SWAY INSTALL
https://youtu.be/dLqnT1rWg20

REAR SWAY INSTALL
https://youtu.be/GBrMeaTSpqs

Hope this helps!

For those of you confused by all the options...

I'm running an H&R front sway bar with a 15mm BMW rear bar. H&R rear is quite stiff for a road car its not that it is wrong... Johnung helped me out a lot when I was considering the upgrade and did Frakle.

[Eschmacher]

Alright, so I've gone through this entire thread and I'm still not sure what to do...
My subframe is going to get dropped soon, so I figured I would explore upgrading the front bar. At the moment, I do not plan on upgrading the rear.

Which bar would be the smallest step up in terms of stiffness from the 335 M-sport bar? (25/22.2). Currently have Eibach prokit springs and B6 EDC dampers. I get quite a bit of body roll and understeer during auto-X. Can see this in my profile pic. I plan on installing millway street camber plates as well, so that should give me a lot more grip up front.

Obviously a stiffer front bar would usually mean more understeer, especially without a rear bar that's been tuned correctly. Perhaps the best option would be to just be to forget about it and leave it stock?

[johnung]

Originally Posted by Eschmacher

Alright, so I've gone through this entire thread and I'm still not sure what to do...
My subframe is going to get dropped soon, so I figured I would explore upgrading the front bar. At the moment, I do not plan on upgrading the rear.

Which bar would be the smallest step up in terms of stiffness from the 335 M-sport bar? (25/22.2). Currently have Eibach prokit springs and B6 EDC dampers. I get quite a bit of body roll and understeer during auto-X. Can see this in my profile pic. I plan on installing millway street camber plates as well, so that should give me a lot more grip up front.

Obviously a stiffer front bar would usually mean more understeer, especially without a rear bar that's been tuned correctly. Perhaps the best option would be to just be to forget about it and leave it stock?

Suspension is a complex subject because there are so many components and forces at play. FaRKle taught me to know what springs you will have before sway bars because their actions in attempting to mitigate body roll overlap.

The stock front sway bar is undersized, which is why the F3x has so much body roll. Heavier and heavier front springs just destroy the ride. It’s just not the way to properly control body roll. The only configuration where I have heard that it might be best to leave the stock front sway bar is with the ridiculously heavy front springs on the Bilstein B16 coilover kit.

I have Eibach springs on my car. The spring rates are a little higher than stock for control without a harsh ride. They really benefit from the H&R 28mm front sway bar. It’s a night and day difference. The car went from excess body roll to cornering flat!

I understand your concern that you could install a thicker front bar and increase understeer. Honestly it didn’t feel that way. Remember all those different forces at play. I think that the 28mm front bar adds so much control by reducing body roll that if understeer increases, it’s not as noticeable.

The front sway bar is a bear to swap out. If you are going to have your subframe dropped I highly recommend doing the H&R front 28mm sway bar at the same time.

Note: H&R makes four slightly different 28mm front bars for the F3x depending on engine and RWD/XDrive. See photo.

You didn’t say which rear sway bar is stock on your car. I’m guessing 12mm-15mm. Realoem can tell you right away. Swapping the rear bar is a piece of cake compared to the front. A buddy of mine who has done them said 3-4 hours. I’m refreshing all of my rear spring/shock rubber bits at the same time. FaRKle did a nice video below.

https://youtu.be/GBrMeaTSpqs

After you get your front end back together, I suggest driving it and getting a real feel for how it handles with the upgraded front sway bar. Then if you decide to go with a thicker rear bar, you have options: 14mm, 15mm, 16mm, 17mm, (might be a 19mm).

It would actually be pretty simple to choose. I’ve already discussed why the H&R 20mm rear bar is a little too heavy. And if you decide to install a thicker rear sway bar you aren’t going to increase by 1mm. You’re going to increase by at least 2mm-3mm. So that really narrows it down.

Hope this helps!

[Watsey]

Originally Posted by Eschmacher

Alright, so I've gone through this entire thread and I'm still not sure what to do...
My subframe is going to get dropped soon, so I figured I would explore upgrading the front bar. At the moment, I do not plan on upgrading the rear.

Which bar would be the smallest step up in terms of stiffness from the 335 M-sport bar? (25/22.2). Currently have Eibach prokit springs and B6 EDC dampers. I get quite a bit of body roll and understeer during auto-X. Can see this in my profile pic. I plan on installing millway street camber plates as well, so that should give me a lot more grip up front.

Obviously a stiffer front bar would usually mean more understeer, especially without a rear bar that's been tuned correctly. Perhaps the best option would be to just be to forget about it and leave it stock?

Anyone that's spent significant time and money on suspension modifications will have their own, and perhaps strong, opinions.

From my own personal experience of a) OEM Sport springs + EDC, b) ACS springs + EDC + poly bushes, c) Ohlins R&T + H&R anti-roll bars + Millway camber plates + poly bushes, d) Onlins R&T + Eibach anti-roll bars + Millway camber plates + poly bushes + monoball bushes, I can assure you that I found the H&R bars too stiff for all-round road use and that I far prefer the Eibach units (especially the rear). Suspension needs a degree of compliance to allow the car to 'flow'. I could lean harder on the H&R bars but snap oversteer was a problem. My track corner speeds were not affected using the Eibach units and the car was more predictable.

Suspension is, of course, a combination of multiple components => springs, dampers, ARBs, bushes, tyres, geometry, to name a few. It's also very subjective in terms of what the driver wants to achieve. Getting it right can empty wallets.

[johnung]

Originally Posted by Watsey

Anyone that's spent significant time and money on suspension modifications will have their own, and perhaps strong, opinions.

From my own personal experience of a) OEM Sport springs + EDC, b) ACS springs + EDC + poly bushes, c) Ohlins R&T + H&R anti-roll bars + Millway camber plates + poly bushes, d) Onlins R&T + Eibach anti-roll bars + Millway camber plates + poly bushes + monoball bushes, I can assure you that I found the H&R bars too stiff for all-round road use and that I far prefer the Eibach units (especially the rear). Suspension needs a degree of compliance to allow the car to 'flow'. I could lean harder on the H&R bars but snap oversteer was a problem. My track corner speeds were not affected using the Eibach units and the car was more predictable.

Suspension is, of course, a combination of multiple components => springs, dampers, ARBs, bushes, tyres, geometry, to name a few. It's also very subjective in terms of what the driver wants to achieve. Getting it right can empty wallets.

We are essentially saying the same thing in terms of sway bars, except you are talking about them in terms of front/rear kits or pairs.

Both sway bar kits that you mentioned use 28mm front sway bars: H&R uses a solid bar and Eibach a hollow bar. I’ve already mentioned my disdain for hollow bars because they are known to snap and my friend died when a front suspension piece snapped on his car.

The H&R solid rear 20mm bar in their kit is too heavy, which causes more oversteer and wheel lift that reduces the size of the tire patch/grip. The Eibach solid rear 16mm bar gives the car more balance. (My stock rear bar was the BMW 12mm) The BMW solid rear 15mm and KC Design solid rear 17mm are two other good rear sway bar options.

ACS and Eibach are typically the same spring & spring rate. The Ohlins springs are probably higher spring rates which could make the H&R sway kit feel exactly how you described.

With my Eibach springs, the H&R front sway bar feels perfect. It’s the H&R rear 20mm bar from their kit that feels too heavy. That’s why I’m swapping it for the KC Design 17mm rear sway bar.

I could use the Eibach rear 16mm bar but it’s difficult to purchase outside their kit in the US. Very easy to obtain separately in Europe. Eibach part number is in the attached photo.

[Eschmacher]

Originally Posted by johnung

You didn’t say which rear sway bar is stock on your car. I’m guessing 12mm-15mm. Realoem can tell you right away.

Appreciate the feedback a lot! As far as I'm aware, my rear bar is the stock m-sport (13mm). I was thinking if I feel I need more rear bar after the front, I would step up to a 15/16mm most likely.

My previous car was a GTI that had full suspension, sway bars, adjustable endlinks, etc. and I was very regretful in how much it all took away from the daily driveability. I've been trying to avoid repeating that on this car lol.

[mixmastermike]

Originally Posted by Eschmacher

Alright, so I've gone through this entire thread and I'm still not sure what to do...
My subframe is going to get dropped soon, so I figured I would explore upgrading the front bar. At the moment, I do not plan on upgrading the rear.

Which bar would be the smallest step up in terms of stiffness from the 335 M-sport bar? (25/22.2). Currently have Eibach prokit springs and B6 EDC dampers. I get quite a bit of body roll and understeer during auto-X. Can see this in my profile pic. I plan on installing millway street camber plates as well, so that should give me a lot more grip up front.

Obviously a stiffer front bar would usually mean more understeer, especially without a rear bar that's been tuned correctly. Perhaps the best option would be to just be to forget about it and leave it stock?

If your lowering the sub frame I'd seriously consider a stiffer bar than a BMW one. The steer in with my H&R front bar is almost flat.

The thinner rear (than H&R) was a reccomendation by Farkle. Having a little more movement in the rear isnt a bad thing at all it keeps ur tires in contact with the road. Consider this if you drive in winter comditions, you will loose traction quicker with a stiffer set up. I know this from driving in a lot of snow. and ice.

As a side note I also have frieds who race cars and if it's very wet they sometimes disconnect the sway bars. Admitantly these are formula Ford's but the reasoning makes sense. Keep the tires in contact with the surface.

Final thought.... I installed the rear 15mm bar first and the back end wanted to let loose a lot which is a really strange feeling in an X-drive. It didnt feel safe so balance is key.

Good luck its all a learning process...