Bilstein B6 on Z3 1.9i stock springs

[mrscalex]

Exactly.

Because I want to fit the B6 on my car (1.9) and it looks like they will raise the front by 10mm I was thinking
if I can replace only the front springs with the M sport 15mm ones and leave the rear stock. This way I will
not change the ride stance and weight distribution.

Is this a good or bad idea?

Beyond my knowledge if a shock itself can change the ride height. Thought only the spring can do that.

 

[hgg]

I thought the same as well, that a shock cannot change the ride height.
It turns out that the high pressure gas monotubes (360psi) are indeed
able to increase the height by a small amount. The problem with the Z3
is that they will raise the front more than the rear. This is most probably
because the rear spring is a lot shorter than the front. Although I am
not 100% sure yet about the later.

 

[Lee]

The Z3 ride height is controlled by the spring, Shock controls the rebound rate, The only options I can see for you are:

Stock ride height (Varies with wheel size)
Sport -15mm
Eibach -30mm

You also have rear spring pads that can vary mm depending on thickness.

If you keep the same spring with new shocks the ride height will roughly be the same.

 

[hgg]

This is true for the majority of oil shocks and oil / low pressure gas shocks of about 40 psi,
but not true for the Bilstein B6 high pressure monotube shocks (360 psi average)

The weight of the car is partially unloaded by the dynamic energy stored in the compressed springs.
If you grab the front wheel fender you will see how easy it is to lift the car by 1cm. On the other hand
if you try to compress the B6 you will see how difficult it is to compress it and the shaft will return
pretty fast as well. It turns out that the B6 is be able to lift the unloaded weight of the Z3 by 1cm.

 

[Lee]

I think your over complicating the matter.

They do list the B6 for the Z3, I very much doubt they will sell you a shock that will make it look like your doing a wheelie.

Long as you dont mix and match the types you'll be fine.

If you dont visit tracks or seriously push your zed I would stick with the B4, they work fine.

 

[hgg]

They do list the B6 for the Z3

For the Z3 1.9 things are a bit confusing.
Bilstein on their front page they list the B6 together with the B12, but when you go
on the online catalog they only list the B4 and the B8. They told me that they are
calling the B8 as B6 for this car...! B8 being the one with the shorter stroke.
So they are suggesting a shorter length shock for stock springs which seems
to me that it will be far worse than a wheelie Z3. Maybe they have in mind only
the Z3s with the sport M suspension.

Anyway, do you know if the B4s are tighter than the stock Sachs shocks?
If they are, I think I will go for the B4s at the end.

 

[Lee]

For the Z3 1.9 things are a bit confusing.
Bilstein on their front page they list the B6 together with the B12, but when you go
on the online catalog they only list the B4 and the B8. They told me that they are
calling the B8 as B6 for this car...! B8 being the one with the shorter stroke.
So they are suggesting a shorter length shock for stock springs which seems
to me that it will be far worse than a wheelie Z3. Maybe they have in mind only
the Z3s with the sport M suspension.

Anyway, do you know if the B4s are tighter than the stock Sachs shocks?
If they are, I think I will go for the B4s at the end.

If they quote the B4 as being OEM I doubt they will be any different.