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      07-21-2016, 11:57 AM   #1
i128
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Bilstein B6 Vs B8 strut

Hello,

I wanted to know if anyone knows the difference between the B6 or B8 strut? I'm set on the Bilsteins as i'm looking for a reliable long-term solution that will perform on the daily.

I have a 128i with factory OE M-sports suspension and don't plan on replacing the OE springs.

Thanks!
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      07-21-2016, 12:30 PM   #2
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Quote:
Originally Posted by i128 View Post
Hello,

I wanted to know if anyone knows the difference between the B6 or B8 strut? I'm set on the Bilsteins as i'm looking for a reliable long-term solution that will perform on the daily.

I have a 128i with factory OE M-sports suspension and don't plan on replacing the OE springs.

Thanks!
For OE M-sport springs, you can go with the B6. B6 is designed to work with springs that don't lower from factory, B8 is designed for springs that lower the car. The body of the B6 is longer than the B8, that's the primary difference. Dampening on the B8 is somewhere between 5 and 10% stiffer to compensate for less shock travel.

So in summary, with stock springs go with the B6.

EDIT: Meant to add, if you plan on upgrading to lowering springs at some point in the future you may want to start with the B8s then. OR - look at buying a kit of both shocks and springs together, the B12 kit for example is a matched set of Eibach pro-kit springs and Bilstein B8s, and the price of that kit is no much more than buying the B6s (B6 is more expensive than the B8 from what I've seen). I've seen the B12 kit for as low as $650USD with free shipping to the US. I just put in a B12 kit myself, bought from a local Toronto vendor that came pretty close in price to buying from the US.
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      07-21-2016, 01:02 PM   #3
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Quote:
Originally Posted by asbrr View Post
For OE M-sport springs, you can go with the B6. B6 is designed to work with springs that don't lower from factory, B8 is designed for springs that lower the car. The body of the B6 is longer than the B8, that's the primary difference. Dampening on the B8 is somewhere between 5 and 10% stiffer to compensate for less shock travel.

So in summary, with stock springs go with the B6.

EDIT: Meant to add, if you plan on upgrading to lowering springs at some point in the future you may want to start with the B8s then. OR - look at buying a kit of both shocks and springs together, the B12 kit for example is a matched set of Eibach pro-kit springs and Bilstein B8s, and the price of that kit is no much more than buying the B6s (B6 is more expensive than the B8 from what I've seen). I've seen the B12 kit for as low as $650USD with free shipping to the US. I just put in a B12 kit myself, bought from a local Toronto vendor that came pretty close in price to buying from the US.

Thanks for the reply. You've pretty much confirmed what I've been reading for the last few hours.

I was looking at the B12 kit as well, as the pricing for that combo is very attractive. I was thinking of getting the B12 kit and selling off the springs. Unfortunately for me the B12 kit comes with B8 and not B6's.

But would there really be any adverse handling effects of installing B8's on OEM sport springs?

Apparently the B4 struts are for the OE springs...
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      07-21-2016, 01:12 PM   #4
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Quote:
Originally Posted by i128 View Post
Thanks for the reply. You've pretty much confirmed what I've been reading for the last few hours.

I was looking at the B12 kit as well, as the pricing for that combo is very attractive. I was thinking of getting the B12 kit and selling off the springs. Unfortunately for me the B12 kit comes with B8 and not B6's.

But would there really be any adverse handling effects of installing B8's on OEM sport springs?

Apparently the B4 struts are for the OE springs...

Well sort of - the B4 is meant as an OE "replacement", and is not an inverted monotube design like the B6 or B8 shocks. I don't know where the damping rates sit for the B4 with respect to OE non-sport and M-sport shocks, maybe somewhere in between? To me, the B6 is still a "performance" damper, just made for "taller" springs, and would upgrade your body control and damping, with some sacrifice on comfort (depends how you define comfort though, if you don't want to feel the road and don't mind floatiness, you'll think the B6 is less comfy than OEM).

Why are you looking to replace your dampers? Are they just old/blown or you're trying to address a particular issue with the OE setup? Will you be driving the car on track at any point? These are all questions you need to explore before arriving at a final answer.

You could run the B8s on the OE springs, I think you'd be running the shock in a somewhat non-optimal damping range so you may not be able to enjoy the full advantages of this upgrade.

If you're dead set on keeping the springs OEM, maybe just stick with the B6 set as you'll have a setup that is designed to operate together.
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      07-21-2016, 07:04 PM   #5
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The problem with combining Bilstein B8 with stock springs is the bump stops will be too short. It will give the front suspension a softer and longer travel.

Normally the solution would be to swap different bump stops. You can't do that with Bilstein B8 because the bump stops are incorporated into the front strut.
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      07-22-2016, 10:25 AM   #6
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Quote:
Originally Posted by John_01 View Post
The problem with combining Bilstein B8 with stock springs is the bump stops will be too short. It will give the front suspension a softer and longer travel.

Normally the solution would be to swap different bump stops. You can't do that with Bilstein B8 because the bump stops are incorporated into the front strut.
Ah, thank you for articulating that properly. It's what I was trying to get at but failed miserably
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      07-22-2016, 02:17 PM   #7
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Quote:
Originally Posted by John_01 View Post
The problem with combining Bilstein B8 with stock springs is the bump stops will be too short. It will give the front suspension a softer and longer travel.

Normally the solution would be to swap different bump stops. You can't do that with Bilstein B8 because the bump stops are incorporated into the front strut.
Do you know if the same applies for th B6's?
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      07-22-2016, 02:42 PM   #8
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Quote:
Originally Posted by i128 View Post
Do you know if the same applies for th B6's?
No - it shouldn't, since B6s are designed for stock spring lengths and are longer so the bump stops won't hit in normal operation. So basically B6 is the "upgrade" replacement for OE, B4 is the "similar" replacement for OE.

The B6 will work with stock springs and provide better body control and overall damping.
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      07-22-2016, 03:04 PM   #9
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Quote:
Originally Posted by asbrr View Post
No - it shouldn't, since B6s are designed for stock spring lengths and are longer so the bump stops won't hit in normal operation. So basically B6 is the "upgrade" replacement for OE, B4 is the "similar" replacement for OE.

The B6 will work with stock springs and provide better body control and overall damping.
Thanks, that's exactly what i'm trying to achieve.

Lastly would you recommend other bits and pieces that I should replace while i'm there replacing the dampers? bushings, screws etc... my car has 102XXX kms on he clock. (about 65,000miles)
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      07-22-2016, 03:44 PM   #10
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Quote:
Originally Posted by i128 View Post
Thanks, that's exactly what i'm trying to achieve.

Lastly would you recommend other bits and pieces that I should replace while i'm there replacing the dampers? bushings, screws etc... my car has 102XXX kms on he clock. (about 65,000miles)
Well, if you are set on just replacing dampers, you will need to take apart your front struts fully, so might as well replace all the small bits:

- Guide support/Strut mount
- Upper & lower spring pads (few bucks each)
- Dust protection collar
- Washer gasket

So that's parts 1,9,12,5,6,7 at a minimum. Technically you should be replacing all the top locknuts also which is part #2. You don't need to replace part numbers 3, 10, & 11 because the B6 comes with their own versions. Part #1 is the most expensive of all, you can get a non-BMW OEM part from a good manufacturer for half the price. Diagram for reference:

http://www.realoem.com/bmw/enUS/show...diagId=31_0695

For the rear, the shock and spring are separate. So you technically don't need to take the springs out to do the work. I would still recommend you replace the upper and lower spring pad, they are only a few bucks each. That's part 8 & 9 here http://www.realoem.com/bmw/enUS/show...diagId=33_1233

For the shock absorber, you should replace parts 5,6,7 in this diagram
http://www.realoem.com/bmw/enUS/show...diagId=33_1233

And also replace part #1 in this diagram
http://www.realoem.com/bmw/enUS/show...diagId=33_1928
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      07-22-2016, 11:01 PM   #11
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I think the most important thing to replace is the Top strut mount for the front. They tend to deteriorate over time as the take a lot of punishment according to the road conditions. You won't want to replace them as a separate job, so this is the ideal time to have them installed for no additional labour cost.

The rear shocks have deformable bushings/mounts at both top and bottom ends. Yours are probably still ok at 65k miles. Some people replace the top mount with stiffer aftermarket parts, especially if you want to use the car for any sort or performance driving. The lower rear shock mount can be replaced as they won't last forever, but that one isn't difficult to get out if you decide to replace them at a later time.
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      07-23-2016, 03:43 AM   #12
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My understanding is that the B4's are an OE replacement. Maybe not exactly like stock, but close enough as far as valving.

The B6's (used to be called HD) and B8's (used to be called Sport) are supposed to be valved identically - the difference is that the B8's are meant to be used with lowering springs and have less suspension travel. So if you're not going to lower the car (or you're going to lower conservatively) it makes more sense to go with the B6's as they will ride better due to the extra suspension travel. If you're going to lower much, you'll probably want the B8's.
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      07-23-2016, 04:08 AM   #13
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Why not just go with a Bilstein kit that has some matched mild lowering springs with it?

Like this kit...
http://www.ajusa.com/Bilstein-46-180...it-acb089.html
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      07-23-2016, 12:46 PM   #14
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Quote:
Originally Posted by Dackelone View Post
Why not just go with a Bilstein kit that has some matched mild lowering springs with it?

Like this kit...
http://www.ajusa.com/Bilstein-46-180...it-acb089.html
This kit covers 2008-2012. Is there any reason not 2008-2013? I've seen this elsewhere for US based parts.
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      07-24-2016, 03:14 PM   #15
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Quote:
Originally Posted by gjm120 View Post
This kit covers 2008-2012. Is there any reason not 2008-2013? I've seen this elsewhere for US based parts.
Probably just a typo. I believe all 1er's are the same suspension wise where they bolt up.

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      07-24-2016, 09:48 PM   #16
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Quote:
Originally Posted by Dackelone View Post
Probably just a typo. I believe all 1er's are the same suspension wise where they bolt up.

Dack
That's what I thought/hoped.
Thanks!
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      11-16-2016, 07:39 PM   #17
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Quote:
Originally Posted by asbrr View Post
For OE M-sport springs, you can go with the B6. B6 is designed to work with springs that don't lower from factory, B8 is designed for springs that lower the car. The body of the B6 is longer than the B8, that's the primary difference. Dampening on the B8 is somewhere between 5 and 10% stiffer to compensate for less shock travel.
Bodies are actually the same...

http://www.1addicts.com/forums/showthread.php?t=1325384

Not sure what to think now.
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      11-17-2016, 01:32 PM   #18
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Quote:
Originally Posted by PrematureApex View Post
Bodies are actually the same...

http://www.1addicts.com/forums/showthread.php?t=1325384

Not sure what to think now.
Huh - weird indeed. Could it be perhaps that the internal chamber is shorter/smaller somehow but the external body is the same? Is that possible?
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      11-20-2016, 10:04 PM   #19
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I've done exactly what you're talking about : B6's with stock Sport Pkg. springs. Works great, no issues at all.
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      11-22-2016, 03:18 PM   #20
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Quote:
Originally Posted by Olgeezer1 View Post
I've done exactly what you're talking about : B6's with stock Sport Pkg. springs. Works great, no issues at all.

How do they match? Do they feel overdampened or underdampened with the m sport springs.
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      12-11-2016, 02:41 PM   #21
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Quote:
Originally Posted by FrostyDC4 View Post
How do they match? Do they feel overdampened or underdampened with the m sport springs.
Not sure how to answer that. They feel just right to me. On the firm side without being harsh, very good rebound control at all speeds. Raised the car very slightly, maybe 1/4". This and getting rid of the runflats = big improvement.
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      05-01-2017, 10:43 PM   #22
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I emailed Bilstein, they replied recommending the B8 to match the Msport springs that come factory fitted with my 135i.

Having a shortened strut length could be a good thing. If it is too long at full extension, it could be to long that the spring could fall out. Of course I do not know how long the wishbones can extend till the springs do drop out.
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