[FaRKle!]

Originally Posted by johnung

Koni Special Active (Red) shocks and struts for a 2015 F30 335i x-Drive. The concern about using any shock with lowered springs is the shock piston travel. The piston travel with these is setup by Koni specifically for the x-Drive suspension. They recommend against using them with springs that aggressively lower the car like the H&R set that drops the car about 1.5" all around. Koni said that the Special Actives will work fine with a moderate lowering spring like the Eibach's (0.8" front, 0.6" rear) or the Dinan's (0.75" drop all around).

I've heard that on some Konis the damping characteristics also depend on where the piston is in the travel, and so if you start out too low/compressed, then the curve isn't very well optimized.

Originally Posted by johnung

Also NOT changing bump stops is less labor since components at top of strut don't have to be touched. Less to go wrong.

How is the labor any different whether you use your OE bump stop or a new one? The top mount still has to come off of the OE front/rear struts/stocks and the bump stop slides right off. I guess if you count pulling the dust boot off of the OE bump stop to put on a new one it could be a minuscule amount of more work.

[johnung]

Good question. That's what I assumed too from struts that I have changed on other cars. But that was the comment that a BMW tech made when he was installing mine. He held the top of the strut assembly up for a second and said "I'm glad we aren't changing the bump stops so I don't have to pull this apart". Then he grabbed the new Koni strut & Eibach spring, and kept going. That was it! I mentioned it as more of a time savings and less components to touch/go wrong rather than saving any money on labor.

[AnimatedDriver]

Originally Posted by johnung

I actually ended up doing the sway bars first on my 335 because the Koni's were delayed shipping from Europe at the time. I had done this before on other cars. The car cornered flat and felt so much tighter going down the road. Of course when the springs and shocks were completed a few weeks later the whole thing worked as a better system.
[…]
My goal was a daily driver that doesn't abuse the family by rattling our teeth on longer drives when we hit potholes or road seams. But when I'm alone on a nice curving road I can really drive it like a real street performance car. For the suspension I ended up going with the H&R sway bars, Eibach Springs and Koni Special Active shocks (technology they designed with McLaren). The three just work together so well as a system.

If it's the body roll that is driving you crazy the most and the installation cost isn't a hindrance, I'd say don't hesitate to do the sway bars first. I've also done sways first with other cars and had great results. I think that sway bars have the biggest effect on cornering by far. Hope this helps.

Any comments on handling in suboptimal conditions, namely soaked roads?
Really interested in reducing body roll for mine, but I spend at least half the year in wet weather.
Already swapped out springs/struts and lowered. RWD.

[johnung]

Originally Posted by AnimatedDriver

Any comments on handling in suboptimal conditions, namely soaked roads?
Really interested in reducing body roll for mine, but I spend at least half the year in wet weather.
Already swapped out springs/struts and lowered. RWD.

Any suspension upgrades that improve handling in dry will do the same in wet.

The mods that had the biggest effect in wet were tires that are highly rated in wet conditions. I have Michelin Pilot Sport 4S. In rain, full crossdrilled brake rotors prevent water from being trapped between rotors and pads. They also have best bite so they improve braking. I use StopTech full crossdrilled rotors.

What year/model do you have? Exactly which parts did you use?

Sway bars focus on limiting body roll so they don’t do much while a car is going straight down the road. However the functionality of springs and sway bars can overlap. So at times the choice of one can affect the choice of another.

One example in an F30 if H&R or Dinan springs were installed which have heavy spring rates, then I wouldn’t choose a rear 19mm or 20mm sway bar. A 16mm/17mm would be better. A heavy rear bar with heavy rear springs might cause lift under heavy cornering, reducing the tire patch.

Another example is Bilstein B16 coilovers which are notorious for super high front spring rates. So leaving the stock front sway bar and installing a heavy 20mm rear sway bar might be recommended.

A typical F3x with typical suspension and tires would benefit by reducing body roll by using a solid front 28mm H&R sway bar and a solid rear Eibach 16mm or solid rear KC Design 17mm sway bar. That would be a balanced combination.

That typical F3x would even benefit from just upgrading the rear sway bar from the stock size which is often 12mm to a solid BMW 15mm, Eibach 16mm or KC Design 17mm. This would help reduce body roll as well as the excessive understeer of the stock F3x suspension.

Note: I only recommend solid sway bars. Hollow bars are cheaper to make so more profitable to manufacture and prone to snapping which can potentially be dangerous.

Hope this helps!

[vcx]

Originally Posted by johnung

Any suspension upgrades that improve handling in dry will do the same in wet.

The mods that had the biggest effect in wet were tires that are highly rated in wet conditions. I have Michelin Pilot Sport 4S. In rain, full crossdrilled brake rotors prevent water from being trapped between rotors and pads. They also have best bite so they improve braking. I use StopTech full crossdrilled rotors.

What year/model do you have? Exactly which parts did you use?

Sway bars focus on limiting body roll so they don’t do much while a car is going straight down the road. However the functionality of springs and sway bars can overlap. So at times the choice of one can affect the choice of another.

One example in an F30 if H&R or Dinan springs were installed which have heavy spring rates, then I wouldn’t choose a rear 19mm or 20mm sway bar. A 16mm/17mm would be better. A heavy rear bar with heavy rear springs might cause lift under heavy cornering, reducing the tire patch.

Another example is Bilstein B16 coilovers which are notorious for super high front spring rates. So leaving the stock front sway bar and installing a heavy 20mm rear sway bar might be recommended.

A typical F3x with typical suspension and tires would benefit by reducing body roll by using a solid front 28mm H&R sway bar and a solid rear Eibach 16mm or solid rear KC Design 17mm sway bar. That would be a balanced combination.

That typical F3x would even benefit from just upgrading the rear sway bar from the stock size which is often 12mm to a solid BMW 15mm, Eibach 16mm or KC Design 17mm. This would help reduce body roll as well as the excessive understeer of the stock F3x suspension.

Note: I only recommend solid sway bars. Hollow bars are cheaper to make so more profitable to manufacture and prone to snapping which can potentially be dangerous.

Hope this helps!

Dear Johnung,

My car is a 2017 340 xdrive 6 speed MT, with adaptive dampers.

After reading your and Farkies advises, my initial plan was to go with the Eibach springs (the higher E10-20-031-06-22 version), F80 bumptstop, H&R 28mm front sway bar, and an Eibach 16mm rear sway bar. I also ordered a f80 bracket with f32 V-shaped struts, to tighten the rear.

But at the moment of ordering those parts, I couldnt order the front H&R 28mm front sway bar only, I had to take it with the rear one (20 mm thick), as a package.

Now I am doubting to install both H&R swaybars, or to stick to my initial plan, and buy the Eibach 16mm rear swaybar (around 250$ more).

It's not a great deal or extra money but, at the same time, I might be inclined to think that if H&R sell their sway bars as a package, they should work well together.

I know that you recommended against a thick sway bar in the rear, when using stiffer springs, as this could lead to tire lift in hard corners.

I also know that Eibach springs are stiffer than stock ones, but not that stiff in absolut.

What would you do ? Just install both front and rear H&R sway bars and call it a day, or just the front H&R sway bar, and buy a thiner (16mm) rear sway bar ?

Thank you very much!

[johnung]

Originally Posted by vcx

Dear Johnung,

My car is a 2017 340 xdrive 6 speed MT, with adaptive dampers.

After reading your and Farkies advises, my initial plan was to go with the Eibach springs (the higher E10-20-031-06-22 version), F80 bumptstop, H&R 28mm front sway bar, and an Eibach 16mm rear sway bar. I also ordered a f80 bracket with f32 V-shaped struts, to tighten the rear.

But at the moment of ordering those parts, I couldnt order the front H&R 28mm front sway bar only, I had to take it with the rear one (20 mm thick), as a package.

Now I am doubting to install both H&R swaybars, or to stick to my initial plan, and buy the Eibach 16mm rear swaybar (around 250$ more).

It's not a great deal or extra money but, at the same time, I might be inclined to think that if H&R sell their sway bars as a package, they should work well together.

I know that you recommended against a thick sway bar in the rear, when using stiffer springs, as this could lead to tire lift in hard corners.

I also know that Eibach springs are stiffer than stock ones, but not that stiff in absolut.

What would you do ? Just install both front and rear H&R sway bars and call it a day, or just the front H&R sway bar, and buy a thiner (16mm) rear sway bar ?

Thank you very much!

What size tires are you using front and rear?

I have an F30 335ix, so essentially same chassis setup as your 340ix. When I installed the H&R Front 28mm and Rear 20mm sway bars with the Eibach -06 XDrive spring kit, FaRKle asked me if I noticed any rear tire lift under heavy cornering, but I didn’t in daily driving. He said that if I tracked the car it might be noticeable.

Note: We aren’t talking about full tire lift here. Just a slight lift from an extra strong rear sway that might slightly reduce the tire contact patch of one rear tire.

After that I tuned the car for more power and really tried to push it hard in high speed freeway on-ramp curves. That’s where I could just about notice it. Also I was on stock sized run flats and winter tires so square 225/45-18 setup. So that’s why I started recommending a slightly smaller solid rear bar than the H&R rear 20mm.

In researching solid rear sway bars I found that my stock rear sway (easily found on realoem website) was 12mm and yours on your 340ix probably is too. On some models BMW installs rear 13mm, 14mm and 15mm bars. So the rear 15mm is an upgrade to a stock rear 12mm bar. Eibach makes a solid 16mm rear bar and KC Design makes a 17mm. Also ST Suspensions makes a 19mm rear bar.

Although I had planned to swap out my H&R 20mm rear sway bar for a KC Design 17mm solid rear sway bar, I’m still using the H&R 20mm solid rear sway bar. I upgraded my tires to Michelin Pilot Sport 4S in square 245/40-18 on the stock 18x8 400M wheels, and now square 255/40-18 on APEX VS-5RS 18x8.5” ET40 (Front 3mm & Rear 5mm spacers make them perfectly flush).

I’ve upgraded my engine power even more now but with the larger rear tires I do not notice any rear lift/reduction in tire patch size at all no matter how hard I push it.

I gave you the entire detailed story so that you and others might have more details to go on to make an informed decision.

If you were on the fence about installing both bars and thinking about maybe upgrading just the rear bar, then I’d suggest the solid rear 16mm or probably 17mm bar. With the 17mm rear, you could add the front solid 28mm later and it would still be pretty balanced.

If yours is a daily driver or a weekend track car I don’t think you can go wrong installing both the H&R Front 28mm and Rear 20mm solid sway bars like I did. You will notice an immediate difference from the original F30 chassis that has a lot of body roll to a car that corners FLAT!

Hope this helps!

[vcx]

Originally Posted by johnung

What size tires are you using front and rear?

I have an F30 335ix, so essentially same chassis setup as your 340ix. When I installed the H&R Front 28mm and Rear 20mm sway bars with the Eibach -06 XDrive spring kit, FaRKle asked me if I noticed any rear tire lift under heavy cornering, but I didn’t in daily driving. He said that if I tracked the car it might be noticeable.

Note: We aren’t talking about full tire lift here. Just a slight lift from an extra strong rear sway that might slightly reduce the tire contact patch of one rear tire.

After that I tuned the car for more power and really tried to push it hard in high speed freeway on-ramp curves. That’s where I could just about notice it. Also I was on stock sized run flats and winter tires so square 225/45-18 setup. So that’s why I started recommending a slightly smaller solid rear bar than the H&R rear 20mm.

In researching solid rear sway bars I found that my stock rear sway (easily found on realoem website) was 12mm and yours on your 340ix probably is too. On some models BMW installs rear 13mm, 14mm and 15mm bars. So the rear 15mm is an upgrade to a stock rear 12mm bar. Eibach makes a solid 16mm rear bar and KC Design makes a 17mm. Also ST Suspensions makes a 19mm rear bar.

Although I had planned to swap out my H&R 20mm rear sway bar for a KC Design 17mm solid rear sway bar, I’m still using the H&R 20mm solid rear sway bar. I upgraded my tires to Michelin Pilot Sport 4S in square 245/40-18 on the stock 18x8 400M wheels, and now square 255/40-18 on APEX VS-5RS 255/40-18.

I’ve upgraded my engine power even more now but with the larger rear tires I do not notice any rear lift/reduction in tire patch size at all no matter how hard I push it.

I gave you the entire detailed story so that you and others might have more details to go on to make an informed decision.

If you were on the fence about installing both bars and thinking about maybe upgrading just the rear bar, then I’d suggest the solid rear 16mm or probably 17mm bar. With the 17mm rear, you could add the front solid 28mm later and it would still be pretty balanced.

If yours is a daily driver or a weekend track car I don’t think you can go wrong installing both the H&R Front 28mm and Rear 20mm solid sway bars like I did. You will notice an immediate difference from the original F30 chassis that has a lot of body roll to a car that corners FLAT!

Hope this helps!

Thank you so much for takingyour time to answer!

My rear wheels are the 18' 255 for summer, and 17' 225 for winter.

After reading your experience, I will probably use the H&R front and rear sway bars.

I usually don't track this car (just sometimes drift on splashed asphalt or ice), and it's essentially a daily driver, so even in spirited driving, I will probably not take corners hard enough to have that issue.

Happy new year!

[sygazelle]

Originally Posted by johnung

Any suspension upgrades that improve handling in dry will do the same in wet.

The mods that had the biggest effect in wet were tires that are highly rated in wet conditions. I have Michelin Pilot Sport 4S. In rain, full crossdrilled brake rotors prevent water from being trapped between rotors and pads. They also have best bite so they improve braking. I use StopTech full crossdrilled rotors.

What year/model do you have? Exactly which parts did you use?

Sway bars focus on limiting body roll so they don’t do much while a car is going straight down the road. However the functionality of springs and sway bars can overlap. So at times the choice of one can affect the choice of another.

One example in an F30 if H&R or Dinan springs were installed which have heavy spring rates, then I wouldn’t choose a rear 19mm or 20mm sway bar. A 16mm/17mm would be better. A heavy rear bar with heavy rear springs might cause lift under heavy cornering, reducing the tire patch.

Another example is Bilstein B16 coilovers which are notorious for super high front spring rates. So leaving the stock front sway bar and installing a heavy 20mm rear sway bar might be recommended.

A typical F3x with typical suspension and tires would benefit by reducing body roll by using a solid front 28mm H&R sway bar and a solid rear Eibach 16mm or solid rear KC Design 17mm sway bar. That would be a balanced combination.

That typical F3x would even benefit from just upgrading the rear sway bar from the stock size which is often 12mm to a solid BMW 15mm, Eibach 16mm or KC Design 17mm. This would help reduce body roll as well as the excessive understeer of the stock F3x suspension.

Note: I only recommend solid sway bars. Hollow bars are cheaper to make so more profitable to manufacture and prone to snapping which can potentially be dangerous.

Hope this helps!

johnung, if there was an award given to the member that consistently provides great information to other members, my vote would be you! Thanks for always providing well-informed responses that directly address the questions being asked and doing so in a humble, non-condescending manner. Happy New Year!

[johnung]

Originally Posted by sygazelle

johnung, if there was an award given to the member that consistently provides great information to other members, my vote would be you! Thanks for always providing well-informed responses that directly address the questions being asked and doing so in a humble, non-condescending manner. Happy New Year!

Thanks so much for the kind words. I just try to pass on information that I have gathered so that it doesn’t just go to waste. Glad that it helps. Happy New Year!

[Polo08816]

Originally Posted by johnung

What size tires are you using front and rear?

I have an F30 335ix, so essentially same chassis setup as your 340ix. When I installed the H&R Front 28mm and Rear 20mm sway bars with the Eibach -06 XDrive spring kit, FaRKle asked me if I noticed any rear tire lift under heavy cornering, but I didn’t in daily driving. He said that if I tracked the car it might be noticeable.

Note: We aren’t talking about full tire lift here. Just a slight lift from an extra strong rear sway that might slightly reduce the tire contact patch of one rear tire.

After that I tuned the car for more power and really tried to push it hard in high speed freeway on-ramp curves. That’s where I could just about notice it. Also I was on stock sized run flats and winter tires so square 225/45-18 setup. So that’s why I started recommending a slightly smaller solid rear bar than the H&R rear 20mm.

In researching solid rear sway bars I found that my stock rear sway (easily found on realoem website) was 12mm and yours on your 340ix probably is too. On some models BMW installs rear 13mm, 14mm and 15mm bars. So the rear 15mm is an upgrade to a stock rear 12mm bar. Eibach makes a solid 16mm rear bar and KC Design makes a 17mm. Also ST Suspensions makes a 19mm rear bar.

Although I had planned to swap out my H&R 20mm rear sway bar for a KC Design 17mm solid rear sway bar, I’m still using the H&R 20mm solid rear sway bar. I upgraded my tires to Michelin Pilot Sport 4S in square 245/40-18 on the stock 18x8 400M wheels, and now square 255/40-18 on APEX VS-5RS 255/40-18.

I’ve upgraded my engine power even more now but with the larger rear tires I do not notice any rear lift/reduction in tire patch size at all no matter how hard I push it.

I gave you the entire detailed story so that you and others might have more details to go on to make an informed decision.

If you were on the fence about installing both bars and thinking about maybe upgrading just the rear bar, then I’d suggest the solid rear 16mm or probably 17mm bar. With the 17mm rear, you could add the front solid 28mm later and it would still be pretty balanced.

If yours is a daily driver or a weekend track car I don’t think you can go wrong installing both the H&R Front 28mm and Rear 20mm solid sway bars like I did. You will notice an immediate difference from the original F30 chassis that has a lot of body roll to a car that corners FLAT!

Hope this helps!

So I asked DVC about this a while ago since he had the H&R sway bars on his car. The tire lift didn't seem to be an issue on the track. His wheel/tire setup at the time was a square set of 275/35/18 on 18x9.5 and Ohlins R&T coilovers.

[johnung]

Originally Posted by Polo08816

So I asked DVC about this a while ago since he had the H&R sway bars on his car. The tire lift didn't seem to be an issue on the track. His wheel/tire setup at the time was a square set of 275/35/18 on 18x9.5 and Ohlins R&T coilovers.

Oh, good. That confirms what I experienced at lower street speeds with square 255/40-18. I’ve been extremely happy with my H&R F28mm/R20mm solid sway bar setup since the day that they were installed. Definitely on my Top Mods List.

[Gryph8n]

How much of the instability in higher speed cornering do you think is from the rear toe angle changing/flexing and suboptimal tire contact? In other words, could this be fixed with coilovers and a rear toe link?…rather than sway bars.

[Lada-1]

Originally Posted by Polo08816

His wheel/tire setup at the time was a square set of 275/35/18 on 18x9.5 and Ohlins R&T coilovers.

How can you fit the front 275 width?

[Polo08816]

Originally Posted by Lada-1

How can you fit the front 275 width?

So I never fit 275 width tires on the front, but the most immediate issue that I saw based on my Ohlins R&T and 255 front tires was that you needed the tire to clear the spring perch. If the overall diameter was just small enough or you have a bit more preload on the coil spring, you'd be able to clear the spring perch, but it would still be very close clearance to the strut / coilover body.

Then you would need a bit of fender rolling and -2.75 to -3.5 camber in the front.