Strut replacement instructions?

[gskrills]

I am looking to replace my shocks and struts on my '89 635 csi but I have a question concerning the struts. I look at kits like bavauto's https://www.bavauto.com/bmw-suspension-kit-ske280016bil and I see the struts have no lower spring perches to hold the spring. Am I missing something here? I am confused as to how the shocks get their lower spring perches.

And if I look at say the catuned coil over kit https://catuned.com/catuned-bmw-coilovers-1-1 it says that you need to weld something to the bottom of the strut and b/c of that they have a core charge. What are they welding on? Does the bavauto kit require welding as well?

[Dschart]

Bav auto kit dampers are stock replacements. The original dampers slide into a tube structure. The lower structure has suspension mountings on the bottom and the lower spring seat and sway bar bracket combined. The dampers are retained by a threaded nut at the top of the structure tube. This design must use original diameter springs and is not adjustable for spring height.

Some aftermarket kits with adjustable spring height require that the tube structure be cut off and new tube/ spring perch welded on.

Are you looking for adjustable springs for racing? If yes, you probably need to cut and weld.


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[Dschart]

Stock design with tube structure on right

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[gskrills]

Dschart thanks so much for the explanation that makes a lot more sense now. I'm not planning to do any track/racing with the car which is why I am likely going to get a stock replacement as opposed to an adjustable coilover system. Do you have a personal recommendation of what kit is the best?

[Dschart]

I run Bilstein B6's all around on my 635. I believe they are a good value. You can get them from Rock Auto for decent cost. They are a bit more firm than stock and are very rigid for geometry due to the larger diameter strut rods. Handling is improved, although the other suspension components need to be in good shape for overall handling. From the sway bar/bushings to the tires and everything between needs to be right.

I run stock springs. If you do change the struts, make sure you have good rubber on the spring seats, and quality strut mounts...the rubber in the strut mounts is the 1st thing that perishes, and can make the struts feel bad. Get all of the parts along with the struts including the bellows and the bumper, and rebuilding the fronts is fairly simple.

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[88m53453]

Don't have enough time right now to explain etc, but your car came with self leveling rear shocks, which is also a strut technically. You will need to know before ordering if your car has been converted already. Look for a hydraulic line going to the lower body of the shock

[DaHose]

If you have the self-adjusting rear shocks, you will see a hydraulic pump in your spare wheel well. The B6's are the best option for a stock height. You can use your stock springs.

Jose

[roger hanley]

If you're deleting the SLS system, new springs will be required for the rear.

[gskrills]

SLS has already been deleted by previous owner.

[MMMEAT]

So on this subject..I just verified that my '85 635CSi has B6s but frankly would love about a 1" drop. I'm kind of amazed that the PO didn't do anything different, spring-wise, as these babies really sit up high, stock. But then I don't want a ridiculously low stance either..Just enough to take away that glaring fender gap. What is the opinion of the group on whether or not B6s are ok to use if going with a mild spring drop? Are H&Rs the best choice? I think I've read that the BavAuto lowering springs are a bit too much for the B6s..

Thanks,

[DaHose]

If you are going to lower the car, then I recommend B8's, with Eibach linear springs. It is a bit low, and doesn't play nice with steep driveways, but parking lot speed bumps, and most street situations are not a problem with my M6. The PO on mine started with 265/35 in rear, and that was pretty harsh. I went to 275/35, and the little bit of extra sidewall really softened the ride. If you are running 17's, you should be just fine with the same setup.

Jose

[Bert Poliakoff]

The problem you will have with B6s is the rear springs will pull out of their perches when you jack the car up. The valving in the B6 vs the B8s are the same. The difference is in the stroke or length of the shaft. The heavy duty has a longer shaft allowing more travel which will pull the shorter springs from the perch.That is why sport shocks are recommended for lowering springs. In the front it doesn't matter as the spring is held captive by the way it is mounted on the strut.

[88m53453]

my favorites are the factory M Technic springs