I've had both.

B6 (yellow) is quite a bit firmer than factory sport. Beyond optimal for a road car, in my experience. Not only are they jarring over sudden bumps they don't keep the tyres in contact with the road as well as less firm dampers. Stiffer isn't always faster on British B roads.

B4 (black) is also a little firmer than factory sport, but is closer and there's not much in it. If you have to have Billies, go for the B4. They're also significantly cheaper.

Also look at Koni. I've heard good things about the orange STR.T Konis, although not tried them myself. (I'm currently running the red Special Active Konis but those were expensive.)

 

Have a read through this:

BUDGET PERFORMANCE SUSPENSION GUIDE (Ultimate E46 OEM+ SACHS Setup)

37415 1. What is this? This guide will walk you through my suggestions for refreshing your E46 suspension using OE BMW parts only. The goal is to achieve increased performance over the original ZHP setup at a lower cost than aftermarket. While written with the ZHP in mind, this guide can be...

www.zhpmafia.com

I personally have Bilstein B4s all around and stock springs as well (although replaced rears with bilstein B3 OE equivalent springs). Regret not going for the Eibach pro-kit but the ride is nice otherwise.

I'd highly recommend Z4 strut mounts in the front as I found the Bilsteins raised my ride height a little and those mounts put them back to stock - perhaps a touch lower.

The best price for both the B4s and Sachs m-sport shocks are on Autodoc. Cheapest on the app and wait for a 38%+ discount.

If you want to lower the car a touch I'd recommend Eibach pro-kit springs as on the thread linked above, just make sure you get the shorter bump stops. That's very important.

 

For a cab, I'd go B4. B6 will rattle everything. My E91 has B6 and I find it firm. For my cab, I went with Sachs sport suspension model. Firm enough.

 

B4 with stock springs is what you want.
No need to change the springs unless they are cracked, corroded, etc.

 

I have bought Bilstein B4 front and rear shocks for @ £233.00 from a great source in Poland.(never had an issue with products from Eastern Europe) (unlike China )

I have tried on real oem to find the part numbers for the springs but to no avail so can you help me please ?
325 2004 convertible.
Many thanks, Mart.

 

I currently have the Bilstein B6 shocks and Eibach springs, and I really like that combination. But if you want the closer to OEM experience you better go for the B4 ones like other people say.

 

I currently have the Bilstein B6 shocks and Eibach springs, and I really like that combination.

I agree. I had that combo (Eibach Pro Kit) on my E39 and one of my past E46 coupes. The B6 with Eibach springs is very nice if you want lowered height and very firm handling. They are much stiffer/harsher compared to stock springs with either Sachs or B4 shocks and struts.

 

I have the Koni Special Actives with my original stock springs and really enjoy them. I've not always heard good things about B4 quality and I didn't want something that is harsher in ride quality.

 

I have blistein b4 and eibach springs, they seem quite good, I recommend this kit,i have wheel 225/45/17

 

close to OEM

Then B4, certainly. Even those are more aggressive than stock...

t

 

Thanks guy`s B4`s it is then with stock springs (if still ok)

Cheers Mart.

 

How to choose the correct Bilstein shock absorber

How to choose the correct Bilstein shock absorber. It can be confusing, do I need B4 or B6? What about B8? What’s the difference? What’s best?

www.bilstein-shocks.co.uk