Bilstein B6 Strut installation in knuckle

[Bry5on]

The bumpstop is internal in B6.

Agree, but the force of the bump stop, when internal, is acting on the strut tube directly (and therefore the strut rubber bushing), rather than the strut mount directly. This means all of the bump stop force is felt in shear through the upper strut bushing until an upper washer limits deflection of the rubber in the strut mount. If there is no washer, you run the risk of shearing the rubber in the strut bearing.

The diameter of the Bilstein strut tube might prevent contact with the hood if the bushing shears, but I’m not 100% on that.

[E46m3zcp]

Tbonem3 is right and this “washer” is not needed according to Bilstein technical support.

I just asked them and got their reply.

[FBloggs]

This is the pounding that the strut mount experiences in normal driving with stock suspension.
The mounting sleeve is being forced upwards by the hammering.
old on the left, new on the right.
The rear takes as much and shear forces from the suspension travel.

[K-Dawg]

Tbonem3 is right and this “washer” is not needed according to Bilstein technical support.

I just asked them and got their reply.

I find it unlikely that anyone at Bilstein who knows what they are talking about would say the washer/spacer is not necessary.

[Tbonem3]

Are you guys jumping your M3s or going off roading?

I've been rocking my washerless setup for 4 years on E46 and almost a year now on E90.

Question - How is the bushing going to shear and shoot upwards when the spring is blocked and can't go up any further? You guys realize the bottom spring perch is fixed to the shock body right?

[eacmen]

I always thought the alignment tab on the bottom of the shock was to prevent rotation in the knuckle. Is it really just the for proper alignment?


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[E46m3zcp]

K-Dawg then you'll have to decide:
A- I am forging this email for some reason or
B- Joseph from Bilstein doesn't know what he's talking about

[E46m3zcp]

BTW, just to make sure, we're all talking about this right?

[Tbonem3]

I always thought the alignment tab on the bottom of the shock was to prevent rotation in the knuckle. Is it really just the for proper alignment?


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Correct. Once clamped, it can't rotate, pin or no pin. Though what force would be acting on it causing it to rotate? What will rotate easily is the top mount's thrust bearing and the damper shaft itself.

[K-Dawg]

Are you guys jumping your M3s or going off roading?

I've been rocking my washerless setup for 4 years on E46 and almost a year now on E90.

Question - How is the bushing going to shear and shoot upwards when the spring is blocked and can't go up any further? You guys realize the bottom spring perch is fixed to the shock body right?

I drive my car on the road, where the car is constantly pushing and pulling on the strut shaft (or the strut shaft is constantly pushing and pulling on the car, depending on perspective). Just because you haven't noticed a problem, doesn't mean that it's right. IIRC, you've also said you don't drive your cars much.

If the strut mount rubber fails, the strut shaft is going to extend as far as it can, possibly contacting the hood.

K-Dawg then you'll have to decide:
A- I am forging this email for some reason or
B- Joseph from Bilstein doesn't know what he's talking about
[/ATTACH]

If Bilstein didn't intend for the washer/spacer to be used, they wouldn't have put a tapered shoulder on the shaft. Without the washer/spacer, that tapered shoulder is acting like a wedge trying to open up the sleeve in the strut mount. The washer is pictured in the instructions, and it used to be specifically mentioned on the Bilstein website (apparently Bilstein has changed their product pages). I recently threw away some notes where I wrote down exactly what it said, but it was something to the effect of "use the stock strut spacer"

E4-WM5-Y207A05.pdf

FWIW, BMW thought that washers were necessary both on bottom and top of the strut mount.

[Tbonem3]

I drive my car on the road, where the car is constantly pushing and pulling on the strut shaft (or the strut shaft is constantly pushing and pulling on the car, depending on perspective). Just because you haven't noticed a problem, doesn't mean that it's right. IIRC, you've also said you don't drive your cars much.

If the strut mount rubber fails, the strut shaft is going to extend as far as it can, possibly contacting the hood.

You didn't answer my question. Once the spring is blocked, the strut shaft will not be extending upwards.

It's incredible how testy a couple of members are here about this bilstein/strut mount stuff.

It reminds me of how angry people got 20 years ago if you didn't use 10w60 oil in these s54/s65/s85s.

[oceansize]

You can pry my 10w60 from my cold dead hands. Remember that dummy (who was actually really knowledgeable but man was he a little Napoleon, think he started his own forum) who went all to pieces because people used leatherique? I mean those were wars some wars over leather conditioner. Dude went bananas.

[K-Dawg]

You didn't answer my question. Once the spring is blocked, the strut shaft will not be extending upwards.

It's incredible how testy a couple of members are here about this bilstein/strut mount stuff.

It reminds me of how angry people got 20 years ago if you didn't use 10w60 oil in these s54/s65/s85s.

If the spring and strut shaft become disconnected due to a failed mount, the strut shaft is going to extend. Just like my wee-wee when I see a thread about this bilstein/strut mount stuff! 😂

[Bry5on]

You didn't answer my question. Once the spring is blocked, the strut shaft will not be extending upwards.

It's incredible how testy a couple of members are here about this bilstein/strut mount stuff.

It reminds me of how angry people got 20 years ago if you didn't use 10w60 oil in these s54/s65/s85s.

That’s actually not true, which might be leading to the confusion. The spring and strut use different mounting points - one through a roller bearing and into the strut mount metal, another through a rubber isolated bushing and into the strut mount metal. Both ultimately load the cast metal strut mount, but only the strut puts its load through the rubber strut mount. Going for factual accuracy here and not personal opinion, the engineered load paths are quite clear.

I daily my car, and I grew up working at my family’s independent BMW (and Mini) service shop and have seen this happen to a car assembled without washers, and as such I would run them on my car. Given that the Bilstein strut diameter is so large, it may prevent a full blown puncture and pass through, but without dimensions, I can’t say one way or another.

An analogy that might be helpful: stock rear shock mounts are rubber and are loaded in similar directions during the drive cycle. It’s more common for those to fail due to repeated shear loads in the rubber. If you can visualize this same failure mode in the shock mount, it might be more clear. Those mounts do not protrude into the trunk because of the presence of the washer underneath them.

Hope this helps folks make an educated call, ultimately it’s up to each person.

Failed strut of a different model car without lower washer installed:


Example of the same failure mode, but in a BMW rear shock mount, installed without its lower washer :

[Bry5on]

K-Dawg then you'll have to decide:
A- I am forging this email for some reason or
B- Joseph from Bilstein doesn't know what he's talking about

They are correct, you do not use the OE washer. I’m understanding from this thread that Bilstein includes their own washer that is installed in place of the OE one.