Rear Bilstein B4 (Sport / Touring) OEM Replacement issue with bump stop washer
 

I'm replacing the rear struts on my 2006 MCS. The B4's I'm using do not have a tapered mount for the washer that goes above the bump stop. I tried to figure out the best way to mount it and was able the get them setup with the washer upside down and pressed into the bump stop. Similar to the OEM setup.

On my test drive there's all kinds of noise coming from the struts. I read another thread on a BMW forum where a guy had a similar issue and ended up not using the washers.

Has anyone else installed these and how did it go? What did you do with the washer?

Thanks.

https://www.northamericanmotoring.co...-assembly.html

There's a video in this thread, sounds like mine.

That is weird for when I pull up pictures of the B4 OE grade they show a large pan washer sitting on a machined perch,

I have also found that the RealOEM templates do not reflect the two piece foam spacers that the first sits between the spring plate and the guide support and then the smaller second one fits on top of the guide support and the concave washer.

Yes, I followed this guide actually. The washer in question is figure 9.

https://cimg8.ibsrv.net/gimg/www.nor...9ea126ce6e.jpg

Also notice that in the user comments - two people describe the same issue I'm having.

I pushed the new bump stop down on the piston, then put the washer concave side UP (opposite from OEM) since the flange is flat on the piston and not tapered like on the oem shock. It's effectively the same setup as stock.

It makes a pretty awful racket. I'm good at wrenching and take my time. The 13mm bolts were torqued to 41 ft/lbs and the large 21mm lower bolt torqued to 106 ft/lbs per the instructions on Pelican Parts. It's not making noise because I missed something or it's not tight.

Does anyone else have these on their car?

End links are tight and not aftermarket?

I had the same problem with the knocking, I posted my results in an earlier post. My struts did not have this washer, I went to the hardware store and got a washer that would fit. I'm still trying to figure out how putting the washer in keeps it from knocking. The bump stop is made to work on the compression of the strut which would push the bump stop up against the top of the strut housing and the bottom half of the strut, with that being said, I added the washer and the thumping stopped.

The washer is dissipating the force from below more evenly across the top plate. Without the piston is able to rotate on the top parts thereby creating the noise??????

What is odd is that my car did not have these washers on either side. It was a one owner car that was only serviced by the stealer, which I have all the service history which shows them changing the struts several times. Who am I kidding, the service history also stated they changed the timing chain guides before they changed the oil pan gasket, when I went to change the oil pan gasket, BIG pieces of TIMING CHAIN GUIDE were in the oil pan....

But I installed the factory washer, so I shouldn't be having this noise. I pushed the washer down into the bump stop like the factory bump stop was.

:confused::confused::confused::confused::confused: :confused::confused::confused::confused::confused: :confused::confused::confused:

End links are stock and were not removed during the install. So no change there.

I literally pulled out the 13mm bolts, the 21mm lower bolt and slid them out. Compressed the spring, and swapped the B4 in, and re-installed.

That's why I wanted to run the washer - the surface area on the piston against that cap would be pretty small and I was worried it might bend without the washer. but now I have a noise.... :no:

The "pipe" extender is still in place between the spring plate and guide support?

I don't have the B4. As a bystander I suspect the knocking is due to the worn 2-piece "rubber" bushing that capture the strut shaft. If you have a high mileage car and these bushing is original, they are likely to long lost their elasticity. I can see the lower one compressed beyond its intended limit and allows the strut to hit the body sheet metal during a compression stoke, causing the knock.

Could this be an issue of not torquing the top strut nut to the proper spec? When I replaced the struts initially they did not make any thumping. Over time, maybe the nut loosened. Putting the washer there may just be a placebo effect and removing the nut and re-torquing the nut may resolve the problem? just my 2cents....

Very unlikely. The top nut's job is to clamp the top washer and the upper spring perch (both functions like washers) against the steel sleeve like a vice's screw. This allows these three parts to "float" within the constraints of the 2-piece "rubber" bushing. If the bushing is tired and old, the floating travel becomes excessive.

Remember, every slightest bump even down to the big gravels on the road these bushing parts get a workout.

One more thought on the synthetic bushing. It is designed to isolate the diamond shape upper suspension flange bracket coming into contact with the strut shaft. When they become tired and old, the shaft may be rubbing and hitting the hole of the flange's center hole as a result of sideways movements. I can see that can cause knocking as well.

https://cimg3.ibsrv.net/gimg/www.nor...56468614b.jpeg

I replaced all of the bushings

Yes

Replaced, see pic. Lemforder.

Not sure how to torque the top since you have to hold it with an allen wrench. I tightened it down until the bushing was nicely squished and there was about 1/2" of threads on top of the nut. Similar to where it was stock.

May be your knocking has nothing to do with the B4s. I had slight knocking. One was caused by new muffler. Once I fixed that, the knock remained. The other as a slightly loose nut on the rear sway bar drop link. The latter took a bit of work to find.

Is the big washer on the last photo came with the B4? My Koni yellow does not come with big washer. The only big washer is the stock one used on the very top which has the concave faces up. There is no big washer on top of the bump stop. The bump stop will rise to the top and stay there by friction.

Here is Koni's "drawing", showing the stock top washer (8) concave up.

https://cimg3.ibsrv.net/gimg/www.nor...aefcea5182.jpg

I wonder if it is possible that in your stackup, the steel sleeve is not being clamped tight by the stackup leaving a gap because of the bushing not being compressed enough. If so I can see you will have knocking on each stroke.