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I have an 88 US 635csi and may be in need of new front struts. I have the SLS in the back and everything is still functional well (imagine that)?!

Is there a setup that allows me to lower the front a little and adjust the SLS ride height in the rear? I have 16” rims and not an overly aggressive driver.

Or if there’s already a thread someone is aware of, please point me in the right direction. Couldn’t find much with SLS components.

you can buy lowering springs for the front that will give about a 1" drop. You can make fine adjustments with the rubber spring pads. These springs work with standard length strut inserts, eg Bilstein HDs (B6). Lowering any more than that gets you into a regime where the camber angles are screwed up enough that you will likely get bad tyre wear unless corrected.

At the rear a (ghetto) solution is to simply cut a turn out of the standard SLS springs, and/or adjust the SLS ride height correction (which is on a closed loop feedback via a linkage) accordingly.

cheers

Hello, I bought my front springs from Ireland Engineering. Lowered front by 1".

looks very nice man, well done

nice one Mr. Bostn635! Do you have SLS in the rear too?

Can anybody recommend a different strut insert other than Billstein? Can't find them anywhere. Backordered from Billstein. I assume i just need the inserts?

Bilstein B6 Performance Shocks - 34-002339

Hello, my SLS was removed years ago. Replaced with Bilsteins and H&R springs.

Back in the day (I think late 90's) when my sls was going out, I decided I will never put much weight in the trunk and it was cheaper to replace the springs and shocks then replace the sls so I decided on the Dinan setup up which included Bilstein shocks. After a coupe years of rear tire wear, tire replacements and alignments, I decided to spend the money on the Dinan adjustable rear subframe kit. I wish I would have done earlier.
Unfort Dinan no longer manufacture anymore E24 products from what I understand but I believe Turner Motorsports and Ireland may have the camber kits. If you want to keep the sls then change the springs, I'm sure that there are folks on this site have done that and can chime in. If not, probably a good idea to get the rear camber kit. Good luck.

I recently installed OE blue-stripe springs from an E30 (PN 31 33 1 127 503) in the front and lowered it by about 1-1.25in. They were the same size overall (height and diameter) but the coils were marginally thinner. Same number of turns. I also opted to retain the SLS since we somewhat recently got it working again. It rides just like it did with the original springs (yellow stripe, don't remember PN, I can go look), but you do have to trim the bump stops a bit. Cheap way to get more low on the front

Thanks all.

Update. I ordered sport springs from Ireland Engineering, but as many spring sets I’ve come to find out do not fit over the sls shock in the rear (slightly too narrow). And NOBODY makes a set of 1” lowering springs that are compatible with sls. Returning the springs and kind of at a loss of what to do. Don’t want mismatched springs front:rear so staying stock for the time being. Unless somebody knows who makes one-off custom springs.

I’ve also looked into late production M6s that had sls and different rear springs, but they are ‘unavailable’ and not sure if M6 sat any lower. The front springs appear to be the same PN, so may have had other suspension differences outside of just springs.

Thanks for all your help. Learning a lot and any ideas welcome.

Thanks Onthefritz. I may look into your option. So it dropped the front and then you adjusted the rear to match? Did you upgrade front strut inserts to make up for the slightly ‘softer’ e30 spring?

clayjo wrote: ↑Fri Sep 07, 2018 1:20 am Thanks Onthefritz. I may look into your option. So it dropped the front and then you adjusted the rear to match? Did you upgrade front strut inserts to make up for the slightly ‘softer’ e30 spring?

That's basically how it happened. At the time, I was experimenting with the rear ride height trying to find a good balance of soft vs stiff in the rear while maintaining decent clearance. I ended up settling on the rear height and finding a solution to adjust the front height later, which ended up being the E30 springs. Thankfully the rear height is so easily adjustable with the self-leveling equipment

I had replaced the front struts with new Bilstein B4s about 9 months prior, and since the operation I haven't noticed any abnormal handling characteristics compared to before. I did have to trim the bump stops, though: I took about 10mm off from the top side (side facing the top hat), and the results have been spot on. If anything, I feel like I need new/rebuilt rear shocks to make the rear equally as firm as the front, but that's to be expected when comparing new parts to old original stuff..

Fritz, how do you adjust the ride height with SLS? Mine is working pretty well...

To adjust height, I decided to re-position the lever arm that clamps on to the anti-roll bar. By rotating it forward or backward, you effectively "trick" the control module into thinking the ride height is higher/lower than it needs to be, and will adjust the fluid pressure to achieve the desired height (as designed to do originally). This has the added effect of stiffening/softening the bound/rebound rate of the shocks due to the lower/higher pressures associated with maintaining a specific ride height (higher pressure/stiffer rate for higher ride height, lower pressure/softer rate for lower height).

Personally, I have found that setting the rear suspension lower yields a softer ride, but too low will make the rear springy as if there were no shocks. Setting too high results in a ride that feels more akin to a work truck than a luxury grand tourer. I just so happened to find the point of best compromise is also the perfect height for the overall aesthetics

I have attached a visualization of how I adjust the height. It takes some mental gymnastics to understand the concepts of the mechanical parts, but it should serve as a good legend for reference. For orientation: this was taken from behind the left rear wheel. The front of the car is frame left, rear is frame right:

Hey thanks much OTF! Excellent explanation and pics.