Bilstein b4 or b6
- Thread starter Sajk
- Start date
As a general rules shocks don't control the height of the car, that's down to the spring length. But - do you actually have an M?
Yes have M. My bad on the shock ride hight.
What do people generally replace Oem shocks with on these? My understanding is that b6 is about 20% firmer than OE which will surely hurt low speed ride quqlity.
Mine is great at speed and well controlled but pretty bad round town over bumps etc. Looking to improve that without compromising control at speed.
What do people generally replace Oem shocks with on these? My understanding is that b6 is about 20% firmer than OE which will surely hurt low speed ride quqlity.
Mine is great at speed and well controlled but pretty bad round town over bumps etc. Looking to improve that without compromising control at speed.
Special Kay
Active member
40%ish off today at autodoc. I'm hoping to grab a set for my car. Just to add to the list of parts and jobs I've got planned for the car :driving:Argenta said:
mmm-five said:
Yes, I currently own 2 M’s (roadster and coupe).
A lot of people write off the factory suspension because they never had the pleasure of owning the car new. So of course when picking up the car secondhand, a tired worn suspension will leave a lot to be desired. The factory struts typically need to be replaced every 50-60k miles. But do an apples-to-apples comparison, and you’d be surprised how good the factory setup is with fresh struts, bushings (fcab rtab, etc), and mounts.
The only time I noticed my coupe understeers is on track during high g corners. But you could never replicate this scenario on any public road, and no off-the-shelf strut like the B6 will remedy this. For the 99% of usage, my coupe with fresh stock hardware handles feels amazing and I will gladly make that trade-off.
To put things in perspective, I am currently in putting my M roadster back to stock so I can list it for sale. It has full aftermarket suspension upgrade but the component I am keeping is the CSL front sway bar to help address the 1% scenario above.
I equate the B6 to a “high-performing” all season tire, i.e. an upgrade in some ways but also a compromise in many. For a sport shock, it does okay but not great on track. For street, it performs nicely on the most perfect road conditions but it’s overly harsh for anything else. Whereas fresh factory hardware is like a Michelin PS4S - it’s fantastic under most conditions and can even handle the occasional track day. However, if you wanted anything better, you might look to a 200tw or R-comp though they won’t last as long (i.e. bringing back to struts, it will need more frequent rebuilds).
The only time I would recommend Bilstein is if you went with their PSS 10 coilovers AND swapped for custom linear springs. But at that point you’ve shelled out enough money you’re not far from getting a higher tier single adjustable setup.
See this thread here
https://z4-forum.com/forum/viewtopic.php?t=138219
Owner upgraded his badly worn stock suspension (with broken springs) for thr B12 kit, which is essentially the B6 struts with Eibach springs (specifically designed to be paired with B6 struts). Yet it didn’t take long for him to realize they’re too harsh and quickly swapped them out for an entry level coilovers. No knock against the BC system but just goes to show how the defacto Bilstein B6 upgrade comes with a lot of caveats.
But if it wasn’t obvious, my recommendation is if you’re sticking with factory springs, go with B4’s which are OE equivalent.
https://z4-forum.com/forum/viewtopic.php?t=138219
Owner upgraded his badly worn stock suspension (with broken springs) for thr B12 kit, which is essentially the B6 struts with Eibach springs (specifically designed to be paired with B6 struts). Yet it didn’t take long for him to realize they’re too harsh and quickly swapped them out for an entry level coilovers. No knock against the BC system but just goes to show how the defacto Bilstein B6 upgrade comes with a lot of caveats.
But if it wasn’t obvious, my recommendation is if you’re sticking with factory springs, go with B4’s which are OE equivalent.
Sajk said:
In general the B4 is a direct OEM replacement. B6 are valved firmer but meant to be paired with factory springs. B8’s are same thing as B6 but meant for lower aftermarket springs.
I know the B4 is offered for the non-M but I don’t recall seeking one for the M. But since your original post specified not wanting to go lower nor make the ride any firmer, seems like OE is your best bet.
Sachs i would think.
