The great Bilstein B6 or B8 mystery

[mrscalex]

To the best of my understanding when Bilstein shocks are discussed on the forum the options mentioned are B4, B6 & B8.

The existence of the B4 is well established and is the direct OEM replacement and a good shock in its own right.

But I've struggled to satisfy myself that there is both a B6 and B8 shock for a Z3.

The B6 shocks Bilstein described in general terms as uprated but with standard stroke. The B8s as uprated with shorter stroke.

I've exchanged a number of messages with Bilstein to understand if there is really a B6 & B8 for a Z3. It's taken quite a while to get to the bottom of it but the most recent message suggests that there is only a B6 shock and this is marketed as B8. Or is it the other way round? Confusing or what! This ties in with what I suspected myself.

Please note, that the BMW Z3 produced with the front axle of the BMW E36 and BMW E30 rear axle. We offered listed BILSTEIN shocks for the BMW E36 3Series as BILSTEIN B8, but the BMW Z3 was produced with a series lowering app. -15mm, so that we defined the B8 for your vehicle as B6 shocks.

The BILSTEIN B12 Pro-Kit is for the BMW Z3 the combination of BILSTEIN B6 shock absorbers with Eibach Pro-Kit lowering springs. You find in the attachment a copy of our catalog.

They go on to say...

Please look at Instagram bilstein_official our video B12 Pro-Kit, we installed the BILSTEIN B12 Pro-Kit suspension in the BMW Z3. The handling and daily driving of the Z3, which are given after the installatio of the B12 Pro-Kit suspension is sportier and more comfortable.

Had a quick look at the video mentioned. I don't use Instagram so maybe I was doing something wrong. But couldn't see anything much to look at. A few pictures and short video clips showing installation and just saying it worked well.

If anyone believes that the B6 and B8 do both exist for a Z3 then could you copy up the respective part numbers? Note there are 2 pairs (left/right) of B6 part numbers kicking around (old and new). But they are both B6 and not B6 & B8.

My conclusion is it's a B6 shock sometimes marketed as a B8. But it could be the other way round...

To be honest all I wanted was a B6 shock so the answer suits me. But it may come as a surprise if you think you have a B8.

For info - definitely no such thing as a B12 shock. That is the name of the Bilstein kit with a B6 or B8 shock and Eibach lowering spring.

 

[Nodzed]

Ok as I understand the B8 is the same rating as the B6 but with a shorter stroke which is what bilstein told me I had to have when I dropped my M 15mm as the B6 was too long, which marries up with what you have said.

 

[mrscalex]

Ok as I understand the B8 is the same rating as the B6 but with a shorter stroke which is what bilstein told me I had to have when I dropped my M 15mm as the B6 was too long, which marries up with what you have said.

My working theory though is there is no real B8. It’s a relabelled B6.

It’s this I’m trying to bottom out.

 

[Nodzed]

My working theory though is there is no real B8. It’s a relabelled B6.

It’s this I’m trying to bottom out.

I think you are totally correct, thats how I understand it, its a shorter throw B6 with the same performance as the B6. The only difference in the length

 

[mrscalex]

I think you are totally correct, thats how I understand it, its a shorter throw B6 with the same performance as the B6. The only difference in the length

Well the devil is in the detail here. So at the risk of over-analysing and potentially causing unnecessary concern/confusion.

My understanding from what Bilstein are telling me is that their Z3 (and it might be different for M) shock range consists of only 2 products:

• B4
• B6. Performance strut but standard stroke length.

B8. There is no B8. No shorter stroke length product. However they sometimes market the B6 as a B8. So what I'm flagging is whether people are buying B8s for their Z3s in name only and actually getting a B6 with standard stroke.

Perhaps someone who has had non-M Bilstein B6/B8 shocks can tell us what part numbers they were supplied with and whether the stroke appeared to be shortened or not?

 

[mrscalex]

Ok as I understand the B8 is the same rating as the B6 but with a shorter stroke which is what bilstein told me I had to have when I dropped my M 15mm as the B6 was too long, which marries up with what you have said.

View attachment 100029

What website and Z model is that? Can you post the link?

 

[Nodzed]

Its for the Z3M and cant remember where it was tbh just google it, Eurocar Parts do the B6 & B8 too

 

[andyglym]

Ok as I understand the B8 is the same rating as the B6 but with a shorter stroke which is what bilstein told me I had to have when I dropped my M 15mm as the B6 was too long, which marries up with what you have said.

View attachment 100029

Looking at the Top and bottom ones they are different in shape, the bottom one has bits protruding that the top one doesn't.

 

[Nodzed]

Well the devil is in the detail here. So at the risk of over-analysing and potentially causing unnecessary concern/confusion.

My understanding from what Bilstein are telling me is that their Z3 (and it might be different for M) shock range consists of only 2 products:

• B4
• B6. Performance strut but standard stroke length.

B8. There is no B8. No shorter stroke length product. However they sometimes market the B6 as a B8. So what I'm flagging is whether people are buying B8s for their Z3s in name only and actually getting a B6 with standard stroke.

Perhaps someone who has had non-M Bilstein B6/B8 shocks can tell us what part numbers they were supplied with and whether the stroke appeared to be shortened or not?

Not what I was told Rob, I was told the B8 is a shorter strut (as in stroke) than the B6 (not saying thats correct just what I was told) as dropping the M 15mm is equivalent to dropping a standard Z3 by 30mm and the B6 was too long??

 

[Nodzed]

There is another point the M and non M struts are different anyway in where the drop links attach maybe theres the difference?

 

[mrscalex]

Sorry @Nodzed no idea on the M. This was meant to be a question about non-M but I might not have been clear about that.

 

[Mario]

Here's what I have

 

[Mario]

And this

 

[billz]

As far as i was made aware when i upgraded the Z3 3.0 Sport the B8 are for lowered Zeds and the B6 is for standard ride height Zeds due to the length of the shock. The B12 kit is to lower the car and comes with B8 shocks

 

[mrscalex]

The trouble is there’s a lot of general knowledge around about B6 and B8 shocks and it’s correct that they are marketed as being for non-lowered and lowered respectively.

The issue is Bilstein’s own catalogues are extremely confusing.

After a lot of time spent yesterday I can now see that Bilstein only market B8 (Sport/Performance Plus) shocks for the Z3. They do not market B6 (HD/Performance) shocks.

However sometimes they refer to the B8 Sport shocks as B6 Sport (note not regular HD or performance labelling). Eh? They are B8 though.

I will post the table later I did to summarise but the bottom line is there isn’t really any Z3 specific front B6/B8 shocks at all. They are carried over from the E36. Bilstein only market the B8 for the Z3. The B6 you won’t find in any Bilstein current catalogue but you can use the E36 listed part.

For the rear, which is Z3 specific, you can only get the B8. So if you put B6 E36s on you will have a mismatched B8 Z3 on the rear. Maybe that doesn’t matter though.

Now all of this may be inconsequential to some. But it is seriously confusing and numerous emails to Bilstein have not helped.

So safest perspective is that you can only fit a matched set of B8s to a Z3. The B6 fitment does not officially exist for a Z3.

Then you have the matter of Sport springs. B4, unofficial/mixed B6 or B8. Which of the 3 is best?

The B4 is marketed for the Z3 in non-Sport length only. However there is a hush-hush E36 B4 with shortened stroke for M-Tech/Sport. Though confusingly the standard E36 B4 standard has a different part number to the Z3. Presumably the E36 parts would be fine on a Z3. They will physically fit but who knows if they are suited mechanically.

If you want a performance (B6/B8) shock for a Z3 Sport (-15mm) spring - which is all I ever wanted to know!, I’m none the wiser.

Use too short a stroke, so potentially B8, on a spring that is too long and you will preload it and potentially get the wrong characteristics.

But as best as I can tell, through the contradictory/unclear/issue skipping emails from Bilstein, the B8 should be used for a Sport spring.

And don’t even bother asking what rides best - B4, B6 or B8. Opinions vary widely and are mostly around standard and -30mm springs. Very little on Sport matching. You might as well ask what the best football team is and expect everyone to say the same thing.

@DrWong will appreciate this thread even if I’ve lost everyone else or sent them to sleep

And if anyone still thinks there are B6 and B8 shocks for a Z3 then I’ll be pleased to see a current catalogue from Bilstein evidenced with the appropriate part numbers. And remember the rear too

No point looking on eBay or supplier sites as they label stuff up wrongly and frequently use wrong or generic images.

 

[DrWong]

Haha, very good effort Rob Gotta say though, I gave up looking into shocks when I found out Monroe's worked for others, precisely because of the confusion in the market. Manufacturers seem to be making it up as they go along. My understanding was B4 is OEM, B6 was sportier, and B8 was sportiest. But then you get inconsistent information from retailers selling Bilsteins and I believe one of them isn't even made any more (B6?).

Anyway I gave up and went with Monroes, which means I'm committed to them when I do the rear shocks. If I was going to do it again I think I'd just get Sachs dampers, as I didn't realise the price difference to Monroes can be fairly negligible if you shop around a little.

 

[mrscalex]

Haha, very good effort Rob Gotta say though, I gave up looking into shocks when I found out Monroe's worked for others, precisely because of the confusion in the market. Manufacturers seem to be making it up as they go along. My understanding was B4 is OEM, B6 was sportier, and B8 was sportiest. But then you get inconsistent information from retailers selling Bilsteins and I believe one of them isn't even made any more (B6?).

Anyway I gave up and went with Monroes, which means I'm committed to them when I do the rear shocks. If I was going to do it again I think I'd just get Sachs dampers, as I didn't realise the price difference to Monroes can be fairly negligible if you shop around a little.

The B6 explanation is embedded in my rambling