[djy5005]

After doing whatever research I could find, I haven't found out the answer to the following question for rear shocks: For a 328i xDrive, will the Bilstein B6 HD shocks show significant improvement over the B4 shocks if I keep the stock springs on the AWD setup? Also, I've seen other posts where for a B8 setup, I would need new springs, but I've also seen some posts where it almost looked like I needed aftermarket springs with the B6 shocks - I don't think this is true, but can anyone clarify?

This is my daily drive, and I don't really want new springs as I have another project Wrangler I'm working on and would like to dump money into that. I'm looking to keep stock ride height, as I don't want to lower the car.

I am leaning towards the B4 because it looks like I can just replace the shocks without the springs, and its essentially OEM with maybe slightly higher gas pressure/improved performance.

However, I see a lot of praise for the B6 HD shocks, but am hesitant to buy them at double the cost of the B4, especially since its a DD, I live in the NYC/NorthNJ area (and don't necessarily want hard suspension with all the potholes), and I haven't really seen anyone state that they're significantly better with stock springs, but rather with aftermarket Eibachs or whatnot.

So, back to the original question: B4 or B6 with stock springs?

[mweisdorfer]

You can get B4 sport version, if wanting something that might give you better Corning. B6 will be a better shock/ strut but you'll pay for them.

[techwhiz]

Stock setup without performance suspension the B6.
If you have performance suspension get the B8.
B4, forget about them.

[oolas3]

Will the B6 raise the front of the car?

nah

[djy5005]

This might be a dumb question, but what are the competitors to the B6? Is the B6 more like the Koni FSDs, where the B8 is more like the Koni Yellows?

Also, what about a "mix and match" for the B6 and B4, B6 in front and the B4's in the rear - would that give too much play in the rear and make the car feel a bit unbalanced?

no, terrible idea

if you've read about them at all, the B6 and B8 are the same damper...only difference is b8 has a shorter shaft to accommodate shorter springs

[djy5005]

Originally Posted by FCobra94

no, terrible idea

if you've read about them at all, the B6 and B8 are the same damper...only difference is b8 has a shorter shaft to accommodate shorter springs

To be honest, I haven't read much about them, but now that you say this it does ring a bell. That said, I'm assuming because they aren't adjustable, that the B6/B8 are competitors to the FSDs? Does Bilstein offer a comparable Koni Yellow solution?

Could you elaborate a little more on why it's bad? I'm not doubting you, just looking to understand the dynamics a little better. I'm assuming that because the dampening rates are different, then it might cause more oscillations?

[chris@strutmonkey]

Get the B6 if you keep your stock xi springs.

[tlow98]

The B4s are a stock replacement damper. They're twin tube design has a relatively soft damping curve.

The B6/8 are nitrogen charged mono tube and are much higher performing than the B4s. Mixing/matching would result in odd performance behavior. Possibly dangerous.

The FSD is sort of the one damper that has no real clear alternative wen cross shopped. They're meant to be sporty and forgiving at the same time. Some people like them, some people don't. I've never tried them but trying to do 2 things well often ends up meaning you're doing poorly at any one thing.

The Koni yellows and bilstein B6/b8 are the most often cross shopped shocks - mostly bc of price and performance goals. The Koni is a higher end twin tube and the bilstein is a stout mono tube. Their performance goals are similar, but how they get there is different.


There are advantages to each. The Koni is a bit cushier around town at low speeds, but the bilstein reigns supreme at higher velocities (both car and shaft speed (speed bumps, etc)).

The best reason to get the Koni is if you like the behavior of a twin tube, but would like adjustability for auto-cross, tracking or the like.

The best reason to buy the Bilstein is if you like a stout shock that can take a beating and perform under duress and are willing to sacrifice a little low speed roughness for high speed bliss. Bilsteins are generally regarded to have higher build quality. Most high end systems are adjustable monotube designs.

Bilstein does make an adjustable mono tube, however, its quite pricey in comparison. (Fronts are ~$500ish each).

Hope this helps!

Originally Posted by tlow98

Hope this helps!

(I didn't quote your whole reply so as to not clutter the thread)

Extremely well said, thank you for sharing...your reply should be a sticky given that this question comes up at least once a week.

[djy5005]

Originally Posted by tlow98

Hope this helps!

Also quoting just to try to add a mess to the thread, but thank you for the clear explanation.

[Jeff@TopGearSolutions]

B4 are similar to OE Spec. They are in essence replacement shocks with the slightest upgrade.

B6 are closer to a sporty shock- used with Original Springs

B8 are sporty but intended for lowered vehicles.

Choose the one that best fits your criteria and goals.

Budget, Sport or Sport with lowered Vehicle.

Also +1 on tlow98's explanation.

[W37V]

Originally Posted by Jeff@TopGearSolutions

B4 are similar to OE Spec. They are in essence replacement shocks with the slightest upgrade.

B6 are closer to a sporty shock- used with Original Springs

B8 are sporty but intended for lowered vehicles.

Choose the one that best fits your criteria and goals.

Budget, Sport or Sport with lowered Vehicle.

Also +1 on tlow98's explanation.

What does this even mean (bolded part)? Why would you add confusion?

B6 is for Non-Sport suspension and XI models with stock springs
B8 is for sport suspension springs and and other aftermarket lowering springs.