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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > B8 vs B12 vs B14



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      03-01-2021, 06:03 PM   #1
lowrydr310
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B8 vs B12 vs B14

I read all the posts discussing these options but they all left me confused and didn't answer all of my questions.

I have two E90s, a 325i with standard suspension and a 330i with sport suspension. I installed new shocks and struts on the 325i two years ago and took a risk on the struts and went with made-in-China barely recognizable brand of complete strut assemblies. Well the saying is true, you get what you pay for. Two years later they're clunking and the boots and bump stops are crumbling. Shocks were KYB with new OEM BMW mounts, and they are still fine.

My 330i had a broken strut mount on one side and a cracked/leaking thrust arm bushing on the other side, so I recently replaced struts with Bilstein B4, Lemforder mounts, and also installed new thrust arms. Now that my 325i needs new struts and I'm giving the car to my nephew soon, I'm thinking of swapping the relatively new B4 struts on my 330i over to the 325i and then upgrading my 330i to something better.

I can't decide between B8, B12, or B14. I have a spare set of OEM Sport springs from a 330i with 60K miles - bought from a forum member - so if I get the B8s I will just swap the springs over. But for just a bit more money than the B8 I can get the B12 or the B14. What's the major difference between these? I don't care about going low, which is why I'm leaning towards the B12 though I do like the idea of adjustability on the B14. From what I can tell the B12 kit is really just the B8 struts with the Eibach pro-kit springs. I did read a few comments that said the strut mounts get trashed because of the internal bump stops on the B8/B12. Is there any truth to that? B14 has the progressive springs and adjustability, with external bump stops.

I'm not really looking to go low at all so looks aren't an issue. I'm just wondering what the performance benefits would be between these three setups. The easy way is the B8 with my spare 60K mile springs, but if the springs included in the B12 or B14 are a better upgrade I may go with them. I'd definitely like some recent opinions about these three kits. It seems most of the reviews I read are several years old.
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      03-03-2021, 09:21 PM   #2
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I have the B12 kit mated with m3 front lower control arms on my 335is and I love it. Gives it a great ride quality and at the same time its nice and firm on the corners. I believe the B12 kit is just a bit different since they claim to have track tested and tweaked, but who knows.
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      03-04-2021, 10:53 AM   #3
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The springs in the B12 kit are tuned to the B8 struts & shocks. That's probably not the case w/ the BMW sport springs. In addition, you can get matched sway bars from Eibach that are also tuned to the B12 kit.
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      03-04-2021, 11:23 AM   #4
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Quote:
Originally Posted by mweisdorfer View Post
The springs in the B12 kit are tuned to the B8 struts & shocks. That's probably not the case w/ the BMW sport springs. In addition, you can get matched sway bars from Eibach that are also tuned to the B12 kit.
Thanks! I was actually going to PM you after seeing some of your posts about suspension, but this is the info I was looking for.

I'm guessing the B14s are matched too, though that doesn't explain why the B14 kit is about $60 cheaper than the B12. Is the B14 going to be more stiff and bouncey than the B12?


Also, I'm an idiot because there's a recent thread in this subforum on this exact topic, where I could have asked my questions instead of starting a new discussion.
I'm not sure I like the compressed upper coils on the third page of that discussion. It looks like when it's adjusted to keep the height high the springs are more compressed. I'm not looking for a big drop, so I'm thinking the B12 may be better for me.

Last edited by lowrydr310; 03-04-2021 at 11:42 AM..
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      03-04-2021, 12:39 PM   #5
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Quote:
Originally Posted by lowrydr310 View Post
Quote:
Originally Posted by mweisdorfer View Post
The springs in the B12 kit are tuned to the B8 struts & shocks. That's probably not the case w/ the BMW sport springs. In addition, you can get matched sway bars from Eibach that are also tuned to the B12 kit.
Thanks! I was actually going to PM you after seeing some of your posts about suspension, but this is the info I was looking for.

I'm guessing the B14s are matched too, though that doesn't explain why the B14 kit is about $60 cheaper than the B12. Is the B14 going to be more stiff and bouncey than the B12?


Also, I'm an idiot because there's a recent thread in this subforum on this exact topic, where I could have asked my questions instead of starting a new discussion.
I'm not sure I like the compressed upper coils on the third page of that discussion. It looks like when it's adjusted to keep the height high the springs are more compressed. I'm not looking for a big drop, so I'm thinking the B12 may be better for me.
You get a drop on the b12. It's about a 1" drop in the front & maybe 1.5" drop in the rear. Keep in mind, it will take all of 2000 miles to settle in.

I'd also do the 11-piece m3 control arm kit & new tie rods while you are in there.

For an extra $310.00, an upgraded sway bar set would really make it ideal.
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