[damack]

I'll start off with a story. I have a 2017 330xi Touring, it's my first BMW and I love it. Coming from a VW Toureg and 4x4 trucks before that, I fell in love with the tight handling of a sporty car. The car has the M-Performance package and for the first 3 months I thought it had the adaptive suspension package. It wasn't until I read a few posts here and got under the car that I found out that it definitely does not. Even after proving to myself that it has the regular shocks, I still felt like selecting sport mode firmed up the suspension. The placebo effect is strong! I've seen a few similar posts here so I guess I'm not entirely crazy. Unfortunately now that I know I don't have the performance suspension, I think it's horrible and needs upgrading. I could have saved a ton of money by just not looking under the car.

So where I'm at now is, I don't really want to lower the car. I'm not completely unsatisfied with the handling but wouldn't mind reducing a bit of roll in the corners. I see a few decent shock upgrades (Bilstein B6 seems good) only a few doing sway bar upgrades, and I don't think I've seen anyone do a swaybar upgrade with the stock dampers. Would this give me what I'm looking for? Less corner roll but still pretty compliant damping over bumps etc?

Interested in the forum's thoughts?

[sspade]

Based on what I'm hearing, the Bilstein B6 option will suit you perfect. This will undoubtedly improve handling characteristics and when combined with the stock springs, won't change your ride height much (if at all).

Adding a stiffer rear sway bar would be the next logical step, but requires lowering the rear subframe. Be careful not to go too stiff, 15mm solid bar seems to be close to the sweet spot. I've got one in storage that I'm waiting to install myself after being quoted a cool grand by the dealer.

I wouldn't bother with the front bar for much of the same reasons above, unless your building an actual track car. Not necessary for most builds. Would be even more challenging to install since your xDrive.

Bottom line... B6 and a slightly stiffer rear bar would do you right.

[FaRKle!]

Originally Posted by damack

I still felt like selecting sport mode firmed up the suspension. The placebo effect is strong!

It's probably from the effect of the stiffer steering. Steering has a large impact on how we feel a car feels. For example, riding shotgun in your car you might feel the ride quality is different than in the driver's seat since you're not getting the feedback or NVH through the steering wheel.

Originally Posted by damack

So where I'm at now is, I don't really want to lower the car. I'm not completely unsatisfied with the handling but wouldn't mind reducing a bit of roll in the corners. I see a few decent shock upgrades (Bilstein B6 seems good) only a few doing sway bar upgrades, and I don't think I've seen anyone do a swaybar upgrade with the stock dampers. Would this give me what I'm looking for? Less corner roll but still pretty compliant damping over bumps etc?

I'm uniquely qualified to comment on this as someone that 1) has an F31 like you, 2) has probably gone through more spring combos than anybody on this forum, and 3) has probably gone though more sway bar combos than anybody on this forum with three different front and three different rear bars (Lancelot might have me tied).

I would first pick what spring rates you're going to go with, then choose dampers, and then sway bars. It's kind of a give/take with springs and sway bars. The stiffer springs you go with, the less sway bar you need/can handle.

Believe it or not, you can get stiffer springs and keep your stock ride height, but the springs that let you do that likely won't be part of a "kit" an aftermarket manufacturer sells. I've been able to piece together kits like that for others using OE springs from different models. I just finished putting together a kit for one F31 member this weekend, and will be doing another for another F31 member this coming week that had goals of making this a bit stiffer while maintaining close to stock ride height.

For OE spring rates, something like a Koni SA or Yellow is probably a better choice of aftermarket damper. Bilsteins (whether they be B6 or 8) really need higher spring rates (like M3/4 ZCP or above) to not be really overdamped IMO. Being overdamped gives a "sporty" feeling, but sacrifices comfort and grip (from what they could be).

If you're looking to stick to around OE spring rates, then pretty much any of the sway bars out there (including the super beefy/strong H&R ones) will be fine and not reduce grip too much at that end. At M3/4 spring rates and above I wouldn't go beyond Dinan (25mm hollow) front bars and 17mm (or Dinan 19mm hollow) rear bars. Beyond those spring rates (typically the coilover range) you shouldn't need to really change either front or rear sway bars, but if you did, don't go above any of the OE offerings in the rear (like the 15mm m240i rear bar).

One negative thing about sway bars is that they increase the side to side coupling. This means that when one side hits a bump, it upsides the opposite more. This is typically why you try to combat roll with springs first, so the suspension sides maintain independence.

From my experience, when I had ~M3/4 spring rates, the H&R 28mm front bar was too stiff and sacrificed too much front end grip. The car didn't want to rotate naturally on the street and track, and the understeer was very prevalent. The 17mm KC Design rear bar was a very nice match to those spring rates though. When I went to even stiffer rear springs (900lbs/in) the 17mm KC design bar was fine for street driving, but it was way too easy break the rear end loose on the track. I've stepped down to a 15mm m240i rear bar now. Note that if you're not tracking the car, then you're unlikely to notice the effects of "too stiff" a rear sway bar. You might see your TC light flicker a bit here and there, but the DSC/DTC system will keep you from sliding out. If I had to choose just one bar to do, it'd definitely be the front bar, not the rear.

Originally Posted by sspade

BI've got one in storage that I'm waiting to install myself after being quoted a cool grand by the dealer.

You've had that FOREVER waiting to install by now, haven't you?

[Littlebear]

Hello BMW Experts!

Below is a link to a good thread; I especially like the table with bar sizes.

https://f30.bimmerpost.com/forums/sh...sway+bar+table

I'm now running stock springs (had M & Dinan in for a while) with bilsteins & M-sport size sways. I like the way the Billys keep the car on its toes, sort of like linear springs compared to progressive springs (Koni).
Plus, I've never broken a Billy, while I've busted too many Konis to count.

Murf