After searching for a few years for some good Bilsteins for my car unsuccessfully, I knew I would have to find and modify something that is available. After much searching for a suitable adaptable shock I came across these, they are the rear shocks from a 1986-1995 BMW 7 series (E32 generation), I found a like new pair from a crashed E32 that I could try and experiment with.
Part number 24 011488 - Bilstein Heavy Duty
Or
F4-B46-1148-H0
I have found these for as little as $108 each new.
Now the spring is supported on the shock body by a small snap ring that fits in a shallow groove in the body however it is too high up for our purposes, I sent the shocks off to the machine shop and had them cut a new groove lower down on the body, It was something like 90mm lower down to match the spring perch height to the stock Girlings. Now you see the body is taller than stock girlings but that is not an issue even on heavily lowered cars like mine, the suspension will bind into the frame before you bottom out these shocks.
Test fit, you can see the new snap ring lower on the body.
The shocks will come with lower spring support ring that tightly fits over the shock's 32mm body, on top of this you could place the factory dmc lower spring cup and them the spring but you would have no adjustablity of the ride height. I instead bought a set of spring height sleeves from Ground Control Engineering (a suspension shop that has all sorts of neat parts like this) that also fit snugly on the Bilsteins body but now can adjust the spring height up or down. This adjuster will require cutting the stock dmc lower cup down so it's internal diameter will allow it to fit over the lockable adjuster.
The last part is the bushings, The lower bushing has a 17mm ID bushing which is far to large to work with the 1/2" lower bolt that our shocks bolt to. I searched for a urethane bushing I could replace that with but could not find one, Then I noticed the OD of the bushing was very similar to the factory lower control arm bushings in our cars, the 1.580" OD and .520" ID was exactly what I needed, It actually pressed right in nice and tight.
For the top I bought new 10mm ID universal urethane bushings also from Ground Control and used the small spacer that came with the shocks as the top stud of the shocks is longer to accommodate a top hat in the BMW
Now installing is just as simple as stock:
The only caveat is the rear tire can rub its side wall on the lower bushing body with 235 or wider tires during hard cornering, I ended up removing the hard sharp edge on the rear side of the lower bushing to prevent any sidewall damage with an angle grinder, The lower bushing are huge and much stronger than stock or much of any other shocks on the market for our cars so removing that corner is not an issue.
So how does it ride? fantastic, I have never had any bad things to say about Billys that I install in nearly all of my vehicles, Its hard to describe but they really do give a very well dampened Germanic feel to the car. They are not too stiff and certainly are not soft and willowy like KYBs. They feel lighter and smoother than the Houston Eibachs which is what I took off for these. Most of all they removed alot of rear road noise, I no longer hear or feel most expansion cracks on the highway that i always felt and heard with the Eibachs and stock Girlings. Also as you notice they are non adjustable, but like all Bilstein monotube shocks you can send them to Bilstein and they can rebuild them and change the valving to anything you want. Sure you could probably get these to feel even better with more tuning, after all they came off the heavy rear end of a bmw's full size flagship sedan and went on a rear engined sports/touring car that weighs nearly half as much. From my experience They work better than anything else Ive tried and are a whole lot cheaper too.
Thanks for looking.
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